diff --git a/.gitignore b/.gitignore
index 78e819ce..ca9c29d0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -23,4 +23,6 @@ doc/api/
 # Further artifacts
 *.exe
 *.zip
-bootstrap
\ No newline at end of file
+bootstrap
+
+.idea
\ No newline at end of file
diff --git a/.analysis_option.yaml b/analysis_options.yaml
similarity index 100%
rename from .analysis_option.yaml
rename to analysis_options.yaml
diff --git a/example/lib/main.dart b/example/lib/main.dart
index bb26dafb..02d0b25c 100644
--- a/example/lib/main.dart
+++ b/example/lib/main.dart
@@ -1,17 +1,17 @@
 import 'package:aws_lambda_dart_runtime/aws_lambda_dart_runtime.dart';
+import 'package:aws_lambda_dart_runtime/runtime/context.dart';
 
 void main() async {
   /// This demo's handling an API Gateway request.
-  final Handler<AwsApiGatewayEvent> helloApiGateway = (context, event) async {
-    final response = {"message": "hello ${context.requestId}"};
+  final helloApiGateway = (Context context, AwsApiGatewayEvent event) async {
+    final response = {'message': 'hello ${context.requestId}'};
 
-    /// it returns an encoded response to the gateway
-    return InvocationResult(
-        context.requestId, AwsApiGatewayResponse.fromJson(response));
+    /// it returns an response to the gateway
+    return AwsApiGatewayResponse.fromJson(response);
   };
 
   /// The Runtime is a singleton. You can define the handlers as you wish.
   Runtime()
-    ..registerHandler<AwsApiGatewayEvent>("hello.apigateway", helloApiGateway)
+    ..registerHandler<AwsApiGatewayEvent>('hello.apigateway', helloApiGateway)
     ..invoke();
 }
diff --git a/example/pubspec.yaml b/example/pubspec.yaml
index 1baa7e49..b19f9a3d 100644
--- a/example/pubspec.yaml
+++ b/example/pubspec.yaml
@@ -1,11 +1,11 @@
 name: example
 
 environment:
-  sdk: ">=2.6.0 <3.0.0"
+  sdk: ">=2.12.0 <3.0.0"
 
 dependencies:
   aws_lambda_dart_runtime:
-    git: https://github.com/awslabs/aws-lambda-dart-runtime.git
+    path: ..
 
 dev_dependencies:
   build_runner:
diff --git a/lib/client/client.dart b/lib/client/client.dart
index b8f7b509..f8ac809f 100644
--- a/lib/client/client.dart
+++ b/lib/client/client.dart
@@ -2,6 +2,8 @@ import 'dart:io';
 import 'dart:async';
 import 'dart:convert';
 
+import 'package:http/http.dart' as http;
+
 /// Next invocation data wraps the data from the
 /// invocation endpoint of the Lambda Runtime Interface.
 class NextInvocation {
@@ -20,43 +22,41 @@ class NextInvocation {
   final String requestId;
 
   /// Deadline milliseconds is the setting for ultimate cancelation of the invocation.
-  final String deadlineMs;
+  final String? deadlineMs;
 
   /// Invoked function ARN is the identifier of the function.
-  final String invokedFunctionArn;
+  final String? invokedFunctionArn;
 
   /// Tracing id is the identifier for tracing like X-Ray.
-  final String traceId;
+  final String? traceId;
 
   /// Client context is the context that is provided to the function.
-  final String clientContext;
+  final String? clientContext;
 
   /// Cognito identity is the identity that maybe is used for authorizing the request.
-  final String cognitoIdentity;
+  final String? cognitoIdentity;
 
   /// Digesting a [HttpClientResponse] into a [NextInvocation].
-  static Future<NextInvocation> fromResponse(
-      HttpClientResponse response) async {
-    return NextInvocation(
-        response: json
-            .decode((await response.transform(Utf8Decoder()).toList()).first),
-        requestId: response.headers.value(runtimeRequestId),
-        deadlineMs: response.headers.value(runtimeDeadlineMs),
-        invokedFunctionArn: response.headers.value(runtimeInvokedFunctionArn),
-        traceId: response.headers.value(runtimeTraceId),
-        clientContext: response.headers.value(runtimeClientContext),
-        cognitoIdentity: response.headers.value(runtimeCognitoIdentity));
-  }
-
-  const NextInvocation(
-      {this.requestId,
-      this.deadlineMs,
-      this.traceId,
-      this.clientContext,
-      this.cognitoIdentity,
-      this.invokedFunctionArn,
-      this.response})
-      : assert(requestId != null);
+  static Future<NextInvocation> fromResponse(http.Response response) async =>
+      NextInvocation(
+          response: (json.decode(utf8.decode(response.bodyBytes)) as Map)
+              .cast<String, dynamic>(),
+          requestId: response.headers[runtimeRequestId]!,
+          deadlineMs: response.headers[runtimeDeadlineMs],
+          invokedFunctionArn: response.headers[runtimeInvokedFunctionArn],
+          traceId: response.headers[runtimeTraceId],
+          clientContext: response.headers[runtimeClientContext],
+          cognitoIdentity: response.headers[runtimeCognitoIdentity]);
+
+  const NextInvocation({
+    required this.requestId,
+    this.deadlineMs,
+    this.traceId,
+    this.clientContext,
+    this.cognitoIdentity,
+    this.invokedFunctionArn,
+    required this.response,
+  });
 }
 
 /// Invocation result is the result that the invoked handler
@@ -71,9 +71,7 @@ class InvocationResult {
   /// any json-encodable data type.
   final dynamic body;
 
-  const InvocationResult(this.requestId, this.body)
-      : assert(requestId != null),
-        assert(body != null);
+  const InvocationResult(this.requestId, this.body) : assert(body != null);
 }
 
 /// Invocation error occurs when there has been an
@@ -92,8 +90,7 @@ class InvocationError {
   /// representation for the Runtime Interface.
   Map<String, dynamic> toJson() => {
         'errorMessage': error.toString(),
-        'errorType': "InvocationError",
-        'stackTrace': this.stackTrace.toString()
+        'errorType': 'InvocationError',
       };
 
   const InvocationError(this.error, this.stackTrace);
@@ -103,7 +100,7 @@ class InvocationError {
 /// It is implemented as a singleton whereby [Client.instance]
 /// always returns the already instantiated client.
 class Client {
-  HttpClient _client;
+  late http.Client _client;
 
   static final Client _singleton = Client._internal();
 
@@ -112,53 +109,45 @@ class Client {
   }
 
   Client._internal() {
-    _client = HttpClient();
+    _client = http.Client();
   }
 
   static const runtimeApiVersion = '2018-06-01';
-  static final runtimeApi = Platform.environment["AWS_LAMBDA_RUNTIME_API"];
 
-  /// Get the next inovation from the AWS Lambda Runtime Interface (see https://docs.aws.amazon.com/lambda/latest/dg/runtimes-api.html).
+  static String? get runtimeApi =>
+      Platform.environment['AWS_LAMBDA_RUNTIME_API'];
+
+  static String? get handlerName => Platform.environment['_HANDLER'];
+
+  /// Get the next invocation from the AWS Lambda Runtime Interface (see https://docs.aws.amazon.com/lambda/latest/dg/runtimes-api.html).
   Future<NextInvocation> getNextInvocation() async {
-    final request = await _client.getUrl(Uri.parse(
-        'http://${runtimeApi}/${runtimeApiVersion}/runtime/invocation/next'));
-    final response = await request.close();
+    final response = await _client.get(Uri.parse(
+        'http://$runtimeApi/$runtimeApiVersion/runtime/invocation/next'));
     return NextInvocation.fromResponse(response);
   }
 
   /// Post the invocation response to the AWS Lambda Runtime Interface.
-  Future<HttpClientResponse> postInvocationResponse(
-      InvocationResult result) async {
-    final request = await _client.postUrl(
+  Future<http.Response> postInvocationResponse(
+      String? requestId, dynamic payload) async {
+    return await _client.post(
       Uri.parse(
-        'http://${runtimeApi}/${runtimeApiVersion}/runtime/invocation/${result.requestId}/response',
+        'http://$runtimeApi/$runtimeApiVersion/runtime/invocation/$requestId/response',
       ),
+      body: jsonEncode(payload),
     );
-    request.add(
-      utf8.encode(
-        json.encode(result.body),
-      ),
-    );
-
-    return await request.close();
   }
 
   /// Post an invocation error to the AWS Lambda Runtime Interface.
   /// It takes in an [InvocationError] and the [requestId]. The [requestId]
   /// is used to map the error to the execution.
-  Future<HttpClientResponse> postInvocationError(
+  Future<http.Response> postInvocationError(
       String requestId, InvocationError err) async {
-    final request = await _client.postUrl(
+    return await _client.post(
       Uri.parse(
-        'http://${runtimeApi}/${runtimeApiVersion}/runtime/invocation/$requestId/error',
+        'http://$runtimeApi/$runtimeApiVersion/runtime/invocation/$requestId/error',
       ),
+      body: jsonEncode(err),
+      headers: {'Content-type': 'application/json'},
     );
-    request.add(
-        utf8.encode(
-            json.encode(err)
-        )
-    );
-
-    return await request.close();
   }
 }
diff --git a/lib/events/alb_event.dart b/lib/events/alb_event.dart
index 05a4f963..b0d0cd0d 100644
--- a/lib/events/alb_event.dart
+++ b/lib/events/alb_event.dart
@@ -1,5 +1,6 @@
 import 'dart:io';
 
+import 'package:aws_lambda_dart_runtime/runtime/event.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'alb_event.g.dart';
@@ -7,50 +8,51 @@ part 'alb_event.g.dart';
 /// Event send by an Application Load Balancer to the
 /// invocation to the Lambda.
 @JsonSerializable()
-class AwsALBEvent {
+class AwsALBEvent extends Event {
   /// Request context in which this request is executed.
   /// For the ELB this is the ARN of the target group.
   @JsonKey()
-  final AwsALBEventContext context;
+  final AwsALBEventContext? context;
 
   /// HTTP method that is used to trigger the invocation of the Lambda.
   @JsonKey()
-  final String httpMethod;
+  final String? httpMethod;
 
   /// The URI that is accessed to trigger the invocation of the Lambda.
   @JsonKey()
-  final String path;
+  final String? path;
 
   /// HTTP headers that are send with the request to the load balancer.
   @JsonKey()
-  final Map<String, dynamic> headers;
+  final Map<String, dynamic>? headers;
 
   /// The query parameters for the request to the load balancer.
   @JsonKey()
-  final Map<String, dynamic> queryStringParameters;
+  final Map<String, dynamic>? queryStringParameters;
 
   /// Body of the request. This can be data that is send with the POST
   /// to the request.
   @JsonKey()
-  final String body;
+  final String? body;
 
   /// Singals that the request is Base64 encoded.
   @JsonKey()
-  final bool isBase64Encoded;
+  final bool? isBase64Encoded;
 
   factory AwsALBEvent.fromJson(Map<String, dynamic> json) =>
       _$AwsALBEventFromJson(json);
 
   Map<String, dynamic> toJson() => _$AwsALBEventToJson(this);
 
-  const AwsALBEvent(
-      {this.context,
-      this.httpMethod,
-      this.path,
-      this.headers,
-      this.queryStringParameters,
-      this.body,
-      this.isBase64Encoded});
+  const AwsALBEvent({
+    this.context,
+    this.httpMethod,
+    this.path,
+    this.headers,
+    this.queryStringParameters,
+    this.body,
+    this.isBase64Encoded,
+  });
 }
 
 /// Response for a request from an Application Load Balancer.
@@ -58,20 +60,20 @@ class AwsALBEvent {
 /// They should reflect the informationen needed here.
 class AwsALBResponse {
   /// The body of the HTTP Response send from the API Gateway to the client.
-  String body;
+  String? body;
 
   /// Indicates if the [body] is Base64 encoded or not. By default is `false`.
-  bool isBase64Encoded;
+  bool? isBase64Encoded;
 
   /// HTTP status code of the response of the API Gateway to the client.
   /// The default status code is `200 OK`.
-  int statusCode;
+  int? statusCode;
 
   /// Description of the send HTTP status code.
-  String statusDescription;
+  String? statusDescription;
 
   /// The HTTP headers that should be send with the response to the client.
-  Map<String, String> headers;
+  Map<String, String>? headers;
 
   /// Returns the JSON representation of the response. This is called by
   /// the JSON encoder to produce the response.
@@ -85,10 +87,10 @@ class AwsALBResponse {
 
   factory AwsALBResponse.fromString(
     String body, {
-    bool isBase64Encoded,
-    int statusCode,
-    String statusDescription,
-    Map<String, String> headers,
+    bool? isBase64Encoded,
+    int? statusCode,
+    String? statusDescription,
+    Map<String, String>? headers,
   }) {
     return AwsALBResponse(
         body: body,
@@ -100,13 +102,18 @@ class AwsALBResponse {
 
   /// The Response that should be returned to the Application Load Balancer.
   /// It is constructed with some default values for the optional parameters.
-  AwsALBResponse(
-      {body, headers, isBase64Encoded, statusCode, statusDescription}) {
+  AwsALBResponse({
+    String? body,
+    Map<String, String>? headers,
+    bool? isBase64Encoded,
+    int? statusCode,
+    String? statusDescription,
+  }) {
     this.body = body ?? '';
     this.isBase64Encoded = isBase64Encoded ?? false;
-    this.headers = headers ?? {"Content-Type": "text/html; charset=utf-8"};
+    this.headers = headers ?? {'Content-Type': 'text/html; charset=utf-8'};
     this.statusCode = statusCode ?? HttpStatus.ok;
-    this.statusDescription = statusDescription ?? "200 OK";
+    this.statusDescription = statusDescription ?? '200 OK';
   }
 }
 
diff --git a/lib/events/alb_event.g.dart b/lib/events/alb_event.g.dart
index f6c69f9f..66010b53 100644
--- a/lib/events/alb_event.g.dart
+++ b/lib/events/alb_event.g.dart
@@ -11,13 +11,13 @@ AwsALBEvent _$AwsALBEventFromJson(Map<String, dynamic> json) {
     context: json['context'] == null
         ? null
         : AwsALBEventContext.fromJson(json['context'] as Map<String, dynamic>),
-    httpMethod: json['httpMethod'] as String,
-    path: json['path'] as String,
-    headers: json['headers'] as Map<String, dynamic>,
+    httpMethod: json['httpMethod'] as String?,
+    path: json['path'] as String?,
+    headers: json['headers'] as Map<String, dynamic>?,
     queryStringParameters:
-        json['queryStringParameters'] as Map<String, dynamic>,
-    body: json['body'] as String,
-    isBase64Encoded: json['isBase64Encoded'] as bool,
+        json['queryStringParameters'] as Map<String, dynamic>?,
+    body: json['body'] as String?,
+    isBase64Encoded: json['isBase64Encoded'] as bool?,
   );
 }
 
diff --git a/lib/events/alexa_event.dart b/lib/events/alexa_event.dart
index 5bf63110..c0198e63 100644
--- a/lib/events/alexa_event.dart
+++ b/lib/events/alexa_event.dart
@@ -1,3 +1,4 @@
+import 'package:aws_lambda_dart_runtime/runtime/event.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'alexa_event.g.dart';
@@ -7,15 +8,15 @@ part 'alexa_event.g.dart';
 class AwsAlexaEventHeader {
   /// Version of the send payload.
   @JsonKey()
-  final String payloadVersion;
+  final String? payloadVersion;
 
   /// Namespace of the event.
   @JsonKey()
-  final String namespace;
+  final String? namespace;
 
   /// Name of the event
   @JsonKey()
-  final String name;
+  final String? name;
 
   factory AwsAlexaEventHeader.fromJson(Map<String, dynamic> json) =>
       _$AwsAlexaEventHeaderFromJson(json);
@@ -28,14 +29,14 @@ class AwsAlexaEventHeader {
 /// Event send by an Application Load Balancer to the
 /// invocation to the Lambda.
 @JsonSerializable()
-class AwsAlexaEvent {
+class AwsAlexaEvent extends Event {
   /// Meta information about the event.
   @JsonKey()
-  final AwsAlexaEventHeader header;
+  final AwsAlexaEventHeader? header;
 
   /// Payload of the event send by Alexa.
   @JsonKey()
-  final Map<String, dynamic> payload;
+  final Map<String, dynamic>? payload;
 
   factory AwsAlexaEvent.fromJson(Map<String, dynamic> json) =>
       _$AwsAlexaEventFromJson(json);
diff --git a/lib/events/alexa_event.g.dart b/lib/events/alexa_event.g.dart
index e94b6c6f..163961b4 100644
--- a/lib/events/alexa_event.g.dart
+++ b/lib/events/alexa_event.g.dart
@@ -8,9 +8,9 @@ part of 'alexa_event.dart';
 
 AwsAlexaEventHeader _$AwsAlexaEventHeaderFromJson(Map<String, dynamic> json) {
   return AwsAlexaEventHeader(
-    namespace: json['namespace'] as String,
-    payloadVersion: json['payloadVersion'] as String,
-    name: json['name'] as String,
+    namespace: json['namespace'] as String?,
+    payloadVersion: json['payloadVersion'] as String?,
+    name: json['name'] as String?,
   );
 }
 
@@ -27,7 +27,7 @@ AwsAlexaEvent _$AwsAlexaEventFromJson(Map<String, dynamic> json) {
     header: json['header'] == null
         ? null
         : AwsAlexaEventHeader.fromJson(json['header'] as Map<String, dynamic>),
-    payload: json['payload'] as Map<String, dynamic>,
+    payload: json['payload'] as Map<String, dynamic>?,
   );
 }
 
diff --git a/lib/events/apigateway_event.dart b/lib/events/apigateway_event.dart
index 83845f2b..c79baacb 100644
--- a/lib/events/apigateway_event.dart
+++ b/lib/events/apigateway_event.dart
@@ -1,6 +1,7 @@
 import 'dart:io';
 import 'dart:convert';
 
+import 'package:aws_lambda_dart_runtime/runtime/event.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'apigateway_event.g.dart';
@@ -11,36 +12,41 @@ part 'apigateway_event.g.dart';
 /// Furthermore it indicates if the [body] is Base64 encoded or not.
 class AwsApiGatewayResponse {
   /// The body of the HTTP Response send from the API Gateway to the client.
-  String body;
+  String? body;
 
   /// Indicates if the [body] is Base64 encoded or not. By default is `false`.
-  bool isBase64Encoded;
+  bool? isBase64Encoded;
 
   // HTTP Status Code of the response of the API Gateway to the client.
-  int statusCode;
+  int? statusCode;
 
   /// The HTTP headers that should be send with the response to the client.
-  Map<String, String> headers;
+  Map<String, String>? headers;
 
   /// Returns the JSON representation of the response. This is called by
   /// the JSON encoder to produce the response.
   Map<String, dynamic> toJson() => {
-        'body': body,
+        if (body != null) 'body': body,
         'isBase64Encoded': isBase64Encoded,
         'statusCode': statusCode,
-        'headers': headers
+        if (headers != null) 'headers': headers
       };
 
   /// The factory creates a new [AwsApiGatewayResponse] from JSON.
   /// It optionally accepts the Base64 encoded flag and a HTTP Status Code
   /// for the response.
-  factory AwsApiGatewayResponse.fromJson(Map<String, dynamic> body,
-      {bool isBase64Encoded, int statusCode, Map<String, String> headers}) {
+  factory AwsApiGatewayResponse.fromJson(
+    Map<String, dynamic> body, {
+    bool isBase64Encoded = false,
+    int statusCode = HttpStatus.ok,
+    Map<String, String>? headers,
+  }) {
     return AwsApiGatewayResponse(
-        body: json.encode(body),
-        isBase64Encoded: isBase64Encoded,
-        headers: headers,
-        statusCode: statusCode);
+      body: json.encode(body),
+      isBase64Encoded: isBase64Encoded,
+      headers: headers,
+      statusCode: statusCode,
+    );
   }
 
   /// The Response that should be returned by the API Gateway for the
@@ -48,55 +54,55 @@ class AwsApiGatewayResponse {
   /// But also it signals if the [body] is Base64 encoded and what the HTTP Status Code
   /// of the response is.
   AwsApiGatewayResponse({
-    String body,
-    bool isBase64Encoded,
-    Map<String, String> headers,
-    int statusCode,
+    String? body,
+    bool isBase64Encoded = false,
+    Map<String, String>? headers,
+    int? statusCode,
   }) {
-    this.body = body ?? '';
-    this.isBase64Encoded = isBase64Encoded ?? false;
-    this.headers = headers ?? {"Content-Type": "application/json"};
+    this.body = body;
+    this.isBase64Encoded = isBase64Encoded;
+    this.headers = headers ?? {'Content-Type': 'application/json'};
     this.statusCode = statusCode ?? HttpStatus.ok;
   }
 }
 
 /// API Gateway Event ...
 @JsonSerializable()
-class AwsApiGatewayEvent {
+class AwsApiGatewayEvent extends Event {
   /// URL Path ...
   @JsonKey()
-  final String path;
+  final String? path;
 
   /// Resource ...
   @JsonKey()
-  final String resource;
+  final String? resource;
 
   /// HTTP Method ...
   @JsonKey()
-  final String httpMethod;
+  final String? httpMethod;
 
   /// Body ...
   @JsonKey()
-  final String body;
+  final String? body;
 
   /// Headers ...
   @JsonKey()
-  final AwsApiGatewayEventHeaders headers;
+  final AwsApiGatewayEventHeaders? headers;
 
   /// Path Parameters ...
   @JsonKey()
-  final Map<String, dynamic> pathParameters;
+  final Map<String, dynamic>? pathParameters;
 
   /// Query String Parameters ...
   @JsonKey()
-  final Map<String, dynamic> queryStringParameters;
+  final Map<String, dynamic>? queryStringParameters;
 
   /// Stage Variables ...
   @JsonKey()
-  final Map<String, dynamic> stageVariables;
+  final Map<String, dynamic>? stageVariables;
 
   /// Request Context ...
-  final AwsApiGatewayEventRequestContext requestContext;
+  final AwsApiGatewayEventRequestContext? requestContext;
 
   factory AwsApiGatewayEvent.fromJson(Map<String, dynamic> json) =>
       _$AwsApiGatewayEventFromJson(json);
@@ -118,62 +124,62 @@ class AwsApiGatewayEvent {
 /// API Gateway Event Headers ...
 @JsonSerializable()
 class AwsApiGatewayEventHeaders {
-  @JsonKey(name: "Accept")
-  final String accept;
+  @JsonKey(name: 'Accept')
+  final String? accept;
 
-  @JsonKey(name: "Accept-Encoding")
-  final String acceptEncoding;
+  @JsonKey(name: 'Accept-Encoding')
+  final String? acceptEncoding;
 
-  @JsonKey(name: "CloudFront-Forwarded-Proto")
-  final String cloudfrontForwardProto;
+  @JsonKey(name: 'CloudFront-Forwarded-Proto')
+  final String? cloudfrontForwardProto;
 
-  @JsonKey(name: "CloudFront-Is-Desktop-Viewer")
-  final String cloudfrontIsDesktopViewer;
+  @JsonKey(name: 'CloudFront-Is-Desktop-Viewer')
+  final String? cloudfrontIsDesktopViewer;
 
-  @JsonKey(name: "CloudFront-Is-Mobile-Viewer")
-  final String cloudfrontIsMobileViewer;
+  @JsonKey(name: 'CloudFront-Is-Mobile-Viewer')
+  final String? cloudfrontIsMobileViewer;
 
-  @JsonKey(name: "CloudFront-Is-SmartTV-Viewer")
-  final String cloudfrontIsSmartTvViewer;
+  @JsonKey(name: 'CloudFront-Is-SmartTV-Viewer')
+  final String? cloudfrontIsSmartTvViewer;
 
-  @JsonKey(name: "CloudFront-Is-Tablet-Viewer")
-  final String cloudfrontIsTabletViewer;
+  @JsonKey(name: 'CloudFront-Is-Tablet-Viewer')
+  final String? cloudfrontIsTabletViewer;
 
-  @JsonKey(name: "CloudFront-Viewer-Country")
-  final String cloudfrontViewerCountry;
+  @JsonKey(name: 'CloudFront-Viewer-Country')
+  final String? cloudfrontViewerCountry;
 
-  @JsonKey(name: "Host")
-  final String host;
+  @JsonKey(name: 'Host')
+  final String? host;
 
-  @JsonKey(name: "Upgrade-Insecure-Requests")
-  final String upgradeInsecureRequests;
+  @JsonKey(name: 'Upgrade-Insecure-Requests')
+  final String? upgradeInsecureRequests;
 
-  @JsonKey(name: "User-Agent")
-  final String userAgent;
+  @JsonKey(name: 'User-Agent')
+  final String? userAgent;
 
-  @JsonKey(name: "Via")
-  final String via;
+  @JsonKey(name: 'Via')
+  final String? via;
 
-  @JsonKey(name: "X-Amz-Cf-Id")
-  final String xAmzCfId;
+  @JsonKey(name: 'X-Amz-Cf-Id')
+  final String? xAmzCfId;
 
-  @JsonKey(name: "X-Forwarded-For")
-  final String xForwardedFor;
+  @JsonKey(name: 'X-Forwarded-For')
+  final String? xForwardedFor;
 
-  @JsonKey(name: "X-Forwarded-Port")
-  final String xForwardedPort;
+  @JsonKey(name: 'X-Forwarded-Port')
+  final String? xForwardedPort;
 
-  @JsonKey(name: "X-Forwarded-Proto")
-  final String xForwardedProto;
+  @JsonKey(name: 'X-Forwarded-Proto')
+  final String? xForwardedProto;
 
-  @JsonKey(name: "Cache-Control")
-  final String cacheControl;
+  @JsonKey(name: 'Cache-Control')
+  final String? cacheControl;
 
-  @JsonKey(name: "X-Amzn-Trace-Id")
-  final String xAmznTraceId;
+  @JsonKey(name: 'X-Amzn-Trace-Id')
+  final String? xAmznTraceId;
 
   @JsonKey(ignore: true)
-  Map<String, dynamic> raw;
+  late Map<String, dynamic> raw;
 
   factory AwsApiGatewayEventHeaders.fromJson(Map<String, dynamic> json) {
     final event = _$AwsApiGatewayEventHeadersFromJson(json);
@@ -209,25 +215,25 @@ class AwsApiGatewayEventHeaders {
 @JsonSerializable()
 class AwsApiGatewayEventRequestContext {
   @JsonKey()
-  final String accountId;
+  final String? accountId;
 
   @JsonKey()
-  final String resourceId;
+  final String? resourceId;
 
   @JsonKey()
-  final String stage;
+  final String? stage;
 
   @JsonKey()
-  final String requestId;
+  final String? requestId;
 
   @JsonKey()
-  final String resourcePath;
+  final String? resourcePath;
 
   @JsonKey()
-  final String httpMethod;
+  final String? httpMethod;
 
   @JsonKey()
-  final String apiId;
+  final String? apiId;
 
   factory AwsApiGatewayEventRequestContext.fromJson(
           Map<String, dynamic> json) =>
@@ -250,37 +256,37 @@ class AwsApiGatewayEventRequestContext {
 @JsonSerializable()
 class AwsApiGatewayEventRequestContextIdentity {
   @JsonKey()
-  final String cognitoIdentityPoolId;
+  final String? cognitoIdentityPoolId;
 
   @JsonKey()
-  final String accountId;
+  final String? accountId;
 
   @JsonKey()
-  final String cognitoIdentityId;
+  final String? cognitoIdentityId;
 
   @JsonKey()
-  final String caller;
+  final String? caller;
 
   @JsonKey()
-  final String apiKey;
+  final String? apiKey;
 
   @JsonKey()
-  final String sourceIp;
+  final String? sourceIp;
 
   @JsonKey()
-  final String cognitoAuthenticationType;
+  final String? cognitoAuthenticationType;
 
   @JsonKey()
-  final String cognitoAuthenticationProvider;
+  final String? cognitoAuthenticationProvider;
 
   @JsonKey()
-  final String userArn;
+  final String? userArn;
 
   @JsonKey()
-  final String userAgent;
+  final String? userAgent;
 
   @JsonKey()
-  final String user;
+  final String? user;
 
   factory AwsApiGatewayEventRequestContextIdentity.fromJson(
           Map<String, dynamic> json) =>
diff --git a/lib/events/apigateway_event.g.dart b/lib/events/apigateway_event.g.dart
index df9aea8d..e1496487 100644
--- a/lib/events/apigateway_event.g.dart
+++ b/lib/events/apigateway_event.g.dart
@@ -8,22 +8,22 @@ part of 'apigateway_event.dart';
 
 AwsApiGatewayEvent _$AwsApiGatewayEventFromJson(Map<String, dynamic> json) {
   return AwsApiGatewayEvent(
-    resource: json['resource'] as String,
-    path: json['path'] as String,
-    httpMethod: json['httpMethod'] as String,
-    body: json['body'] as String,
+    resource: json['resource'] as String?,
+    path: json['path'] as String?,
+    httpMethod: json['httpMethod'] as String?,
+    body: json['body'] as String?,
     headers: json['headers'] == null
         ? null
         : AwsApiGatewayEventHeaders.fromJson(
             json['headers'] as Map<String, dynamic>),
     queryStringParameters:
-        json['queryStringParameters'] as Map<String, dynamic>,
-    stageVariables: json['stageVariables'] as Map<String, dynamic>,
+        json['queryStringParameters'] as Map<String, dynamic>?,
+    stageVariables: json['stageVariables'] as Map<String, dynamic>?,
     requestContext: json['requestContext'] == null
         ? null
         : AwsApiGatewayEventRequestContext.fromJson(
             json['requestContext'] as Map<String, dynamic>),
-    pathParameters: json['pathParameters'] as Map<String, dynamic>,
+    pathParameters: json['pathParameters'] as Map<String, dynamic>?,
   );
 }
 
@@ -43,24 +43,24 @@ Map<String, dynamic> _$AwsApiGatewayEventToJson(AwsApiGatewayEvent instance) =>
 AwsApiGatewayEventHeaders _$AwsApiGatewayEventHeadersFromJson(
     Map<String, dynamic> json) {
   return AwsApiGatewayEventHeaders(
-    accept: json['Accept'] as String,
-    acceptEncoding: json['Accept-Encoding'] as String,
-    cloudfrontIsDesktopViewer: json['CloudFront-Is-Desktop-Viewer'] as String,
-    cloudfrontIsMobileViewer: json['CloudFront-Is-Mobile-Viewer'] as String,
-    cloudfrontIsSmartTvViewer: json['CloudFront-Is-SmartTV-Viewer'] as String,
-    cloudfrontForwardProto: json['CloudFront-Forwarded-Proto'] as String,
-    cloudfrontIsTabletViewer: json['CloudFront-Is-Tablet-Viewer'] as String,
-    cloudfrontViewerCountry: json['CloudFront-Viewer-Country'] as String,
-    upgradeInsecureRequests: json['Upgrade-Insecure-Requests'] as String,
-    cacheControl: json['Cache-Control'] as String,
-    host: json['Host'] as String,
-    via: json['Via'] as String,
-    userAgent: json['User-Agent'] as String,
-    xAmzCfId: json['X-Amz-Cf-Id'] as String,
-    xAmznTraceId: json['X-Amzn-Trace-Id'] as String,
-    xForwardedFor: json['X-Forwarded-For'] as String,
-    xForwardedPort: json['X-Forwarded-Port'] as String,
-    xForwardedProto: json['X-Forwarded-Proto'] as String,
+    accept: json['Accept'] as String?,
+    acceptEncoding: json['Accept-Encoding'] as String?,
+    cloudfrontIsDesktopViewer: json['CloudFront-Is-Desktop-Viewer'] as String?,
+    cloudfrontIsMobileViewer: json['CloudFront-Is-Mobile-Viewer'] as String?,
+    cloudfrontIsSmartTvViewer: json['CloudFront-Is-SmartTV-Viewer'] as String?,
+    cloudfrontForwardProto: json['CloudFront-Forwarded-Proto'] as String?,
+    cloudfrontIsTabletViewer: json['CloudFront-Is-Tablet-Viewer'] as String?,
+    cloudfrontViewerCountry: json['CloudFront-Viewer-Country'] as String?,
+    upgradeInsecureRequests: json['Upgrade-Insecure-Requests'] as String?,
+    cacheControl: json['Cache-Control'] as String?,
+    host: json['Host'] as String?,
+    via: json['Via'] as String?,
+    userAgent: json['User-Agent'] as String?,
+    xAmzCfId: json['X-Amz-Cf-Id'] as String?,
+    xAmznTraceId: json['X-Amzn-Trace-Id'] as String?,
+    xForwardedFor: json['X-Forwarded-For'] as String?,
+    xForwardedPort: json['X-Forwarded-Port'] as String?,
+    xForwardedProto: json['X-Forwarded-Proto'] as String?,
   );
 }
 
@@ -90,13 +90,13 @@ Map<String, dynamic> _$AwsApiGatewayEventHeadersToJson(
 AwsApiGatewayEventRequestContext _$AwsApiGatewayEventRequestContextFromJson(
     Map<String, dynamic> json) {
   return AwsApiGatewayEventRequestContext(
-    accountId: json['accountId'] as String,
-    resourceId: json['resourceId'] as String,
-    stage: json['stage'] as String,
-    requestId: json['requestId'] as String,
-    resourcePath: json['resourcePath'] as String,
-    httpMethod: json['httpMethod'] as String,
-    apiId: json['apiId'] as String,
+    accountId: json['accountId'] as String?,
+    resourceId: json['resourceId'] as String?,
+    stage: json['stage'] as String?,
+    requestId: json['requestId'] as String?,
+    resourcePath: json['resourcePath'] as String?,
+    httpMethod: json['httpMethod'] as String?,
+    apiId: json['apiId'] as String?,
   );
 }
 
@@ -116,18 +116,18 @@ AwsApiGatewayEventRequestContextIdentity
     _$AwsApiGatewayEventRequestContextIdentityFromJson(
         Map<String, dynamic> json) {
   return AwsApiGatewayEventRequestContextIdentity(
-    cognitoIdentityPoolId: json['cognitoIdentityPoolId'] as String,
+    cognitoIdentityPoolId: json['cognitoIdentityPoolId'] as String?,
     cognitoAuthenticationProvider:
-        json['cognitoAuthenticationProvider'] as String,
-    cognitoAuthenticationType: json['cognitoAuthenticationType'] as String,
-    caller: json['caller'] as String,
-    accountId: json['accountId'] as String,
-    cognitoIdentityId: json['cognitoIdentityId'] as String,
-    apiKey: json['apiKey'] as String,
-    sourceIp: json['sourceIp'] as String,
-    user: json['user'] as String,
-    userAgent: json['userAgent'] as String,
-    userArn: json['userArn'] as String,
+        json['cognitoAuthenticationProvider'] as String?,
+    cognitoAuthenticationType: json['cognitoAuthenticationType'] as String?,
+    caller: json['caller'] as String?,
+    accountId: json['accountId'] as String?,
+    cognitoIdentityId: json['cognitoIdentityId'] as String?,
+    apiKey: json['apiKey'] as String?,
+    sourceIp: json['sourceIp'] as String?,
+    user: json['user'] as String?,
+    userAgent: json['userAgent'] as String?,
+    userArn: json['userArn'] as String?,
   );
 }
 
diff --git a/lib/events/appsync_event.dart b/lib/events/appsync_event.dart
index 3223f6be..0a6ad7a9 100644
--- a/lib/events/appsync_event.dart
+++ b/lib/events/appsync_event.dart
@@ -1,18 +1,19 @@
+import 'package:aws_lambda_dart_runtime/runtime/event.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'appsync_event.g.dart';
 
 /// App Sync Event ...
 @JsonSerializable()
-class AwsAppSyncEvent {
-  @JsonKey(name: "version")
-  final String version;
+class AwsAppSyncEvent extends Event {
+  @JsonKey(name: 'version')
+  final String? version;
 
-  @JsonKey(name: "operation")
-  final String operation;
+  @JsonKey(name: 'operation')
+  final String? operation;
 
-  @JsonKey(name: "payload")
-  final String payload;
+  @JsonKey(name: 'payload')
+  final String? payload;
 
   factory AwsAppSyncEvent.fromJson(Map<String, dynamic> json) =>
       _$AwsAppSyncEventFromJson(json);
diff --git a/lib/events/appsync_event.g.dart b/lib/events/appsync_event.g.dart
index 6ff0c8f3..edf22c6a 100644
--- a/lib/events/appsync_event.g.dart
+++ b/lib/events/appsync_event.g.dart
@@ -8,9 +8,9 @@ part of 'appsync_event.dart';
 
 AwsAppSyncEvent _$AwsAppSyncEventFromJson(Map<String, dynamic> json) {
   return AwsAppSyncEvent(
-    version: json['version'] as String,
-    operation: json['operation'] as String,
-    payload: json['payload'] as String,
+    version: json['version'] as String?,
+    operation: json['operation'] as String?,
+    payload: json['payload'] as String?,
   );
 }
 
diff --git a/lib/events/cloudwatch_event.dart b/lib/events/cloudwatch_event.dart
index 28aa9013..96d588f6 100644
--- a/lib/events/cloudwatch_event.dart
+++ b/lib/events/cloudwatch_event.dart
@@ -1,3 +1,4 @@
+import 'package:aws_lambda_dart_runtime/runtime/event.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'cloudwatch_event.g.dart';
@@ -22,38 +23,38 @@ part 'cloudwatch_event.g.dart';
 /// }
 /// ```
 @JsonSerializable()
-class AwsCloudwatchEvent {
+class AwsCloudwatchEvent extends Event {
   /// Resources ...
   @JsonKey()
-  final List<String> resources;
+  final List<String>? resources;
 
   /// Region ...
   @JsonKey()
-  final String region;
+  final String? region;
 
   /// Id ...
   @JsonKey()
-  final String id;
+  final String? id;
 
   /// Source ...
   @JsonKey()
-  final String source;
+  final String? source;
 
   /// Account ...
   @JsonKey()
-  final String account;
+  final String? account;
 
   /// Data Type ...
-  @JsonKey(name: "detail-type")
-  final String detailType;
+  @JsonKey(name: 'detail-type')
+  final String? detailType;
 
   /// Detail ...
   @JsonKey()
-  final Map<String, dynamic> detail;
+  final Map<String, dynamic>? detail;
 
   /// Time ...
   @JsonKey()
-  final DateTime time;
+  final DateTime? time;
 
   factory AwsCloudwatchEvent.fromJson(Map<String, dynamic> json) =>
       _$AwsCloudwatchEventFromJson(json);
diff --git a/lib/events/cloudwatch_event.g.dart b/lib/events/cloudwatch_event.g.dart
index c14b9eac..1726f885 100644
--- a/lib/events/cloudwatch_event.g.dart
+++ b/lib/events/cloudwatch_event.g.dart
@@ -8,13 +8,14 @@ part of 'cloudwatch_event.dart';
 
 AwsCloudwatchEvent _$AwsCloudwatchEventFromJson(Map<String, dynamic> json) {
   return AwsCloudwatchEvent(
-    resources: (json['resources'] as List)?.map((e) => e as String)?.toList(),
-    region: json['region'] as String,
-    id: json['id'] as String,
-    source: json['source'] as String,
-    account: json['account'] as String,
-    detailType: json['detail-type'] as String,
-    detail: json['detail'] as Map<String, dynamic>,
+    resources:
+        (json['resources'] as List<dynamic>?)?.map((e) => e as String).toList(),
+    region: json['region'] as String?,
+    id: json['id'] as String?,
+    source: json['source'] as String?,
+    account: json['account'] as String?,
+    detailType: json['detail-type'] as String?,
+    detail: json['detail'] as Map<String, dynamic>?,
     time: json['time'] == null ? null : DateTime.parse(json['time'] as String),
   );
 }
diff --git a/lib/events/cloudwatch_log_event.dart b/lib/events/cloudwatch_log_event.dart
index ea7ab929..366469e9 100644
--- a/lib/events/cloudwatch_log_event.dart
+++ b/lib/events/cloudwatch_log_event.dart
@@ -1,3 +1,4 @@
+import 'package:aws_lambda_dart_runtime/runtime/event.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'cloudwatch_log_event.g.dart';
@@ -10,10 +11,10 @@ part 'cloudwatch_log_event.g.dart';
 
 /// Cloudwatch Log Event ...
 @JsonSerializable()
-class AwsCloudwatchLogEvent {
+class AwsCloudwatchLogEvent extends Event {
   /// awslogs ...
   @JsonKey()
-  final Map<String, dynamic> awslogs;
+  final Map<String, dynamic>? awslogs;
 
   factory AwsCloudwatchLogEvent.fromJson(Map<String, dynamic> json) =>
       _$AwsCloudwatchLogEventFromJson(json);
diff --git a/lib/events/cloudwatch_log_event.g.dart b/lib/events/cloudwatch_log_event.g.dart
index 73a181d1..dd032b02 100644
--- a/lib/events/cloudwatch_log_event.g.dart
+++ b/lib/events/cloudwatch_log_event.g.dart
@@ -9,7 +9,7 @@ part of 'cloudwatch_log_event.dart';
 AwsCloudwatchLogEvent _$AwsCloudwatchLogEventFromJson(
     Map<String, dynamic> json) {
   return AwsCloudwatchLogEvent(
-    awslogs: json['awslogs'] as Map<String, dynamic>,
+    awslogs: json['awslogs'] as Map<String, dynamic>?,
   );
 }
 
diff --git a/lib/events/cognito_event.dart b/lib/events/cognito_event.dart
index 4c8862f3..99baf2df 100644
--- a/lib/events/cognito_event.dart
+++ b/lib/events/cognito_event.dart
@@ -1,32 +1,33 @@
+import 'package:aws_lambda_dart_runtime/runtime/event.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'cognito_event.g.dart';
 
 @JsonSerializable()
-class AwsCognitoEvent {
+class AwsCognitoEvent extends Event {
   @JsonKey()
-  final int version;
+  final int? version;
 
   @JsonKey()
-  final String triggerSource;
+  final String? triggerSource;
 
   @JsonKey()
-  final String region;
+  final String? region;
 
   @JsonKey()
-  final String userPoolId;
+  final String? userPoolId;
 
   @JsonKey()
-  final String userName;
+  final String? userName;
 
   @JsonKey()
-  final Map<String, String> callerContext;
+  final Map<String, String>? callerContext;
 
   @JsonKey()
-  final AwsCognitoRequest request;
+  final AwsCognitoRequest? request;
 
   @JsonKey()
-  final AwsCognitoResponse response;
+  final AwsCognitoResponse? response;
 
   const AwsCognitoEvent(
       {this.version,
@@ -47,25 +48,25 @@ class AwsCognitoEvent {
 @JsonSerializable()
 class AwsCognitoRequest {
   @JsonKey()
-  final Map<String, dynamic> userAttributes;
+  final Map<String, dynamic>? userAttributes;
 
   @JsonKey()
-  final Map<String, String> validationData;
+  final Map<String, String>? validationData;
 
   @JsonKey()
-  final Map<String, String> clientMetadata;
+  final Map<String, String>? clientMetadata;
 
   @JsonKey()
-  final bool newDeviceUsed;
+  final bool? newDeviceUsed;
 
   @JsonKey()
-  final AwsGroupConfiguration groupConfiguration;
+  final AwsGroupConfiguration? groupConfiguration;
 
   @JsonKey()
-  final String password;
+  final String? password;
 
   @JsonKey()
-  final String codeParameter;
+  final String? codeParameter;
 
   const AwsCognitoRequest(
       {this.userAttributes,
@@ -85,40 +86,40 @@ class AwsCognitoRequest {
 @JsonSerializable()
 class AwsCognitoResponse {
   @JsonKey()
-  final bool autoConfirmUser;
+  final bool? autoConfirmUser;
 
   @JsonKey()
-  final bool autoVerifyPhone;
+  final bool? autoVerifyPhone;
 
   @JsonKey()
-  final bool autoVerifyEmail;
+  final bool? autoVerifyEmail;
 
   @JsonKey()
-  final AwsClaimOverrideDetails claimsOverrideDetails;
+  final AwsClaimOverrideDetails? claimsOverrideDetails;
 
   @JsonKey()
-  final Map<String, String> userAttributes;
+  final Map<String, String>? userAttributes;
 
   @JsonKey()
-  final String finalUserStatus;
+  final String? finalUserStatus;
 
   @JsonKey()
-  final String messageAction;
+  final String? messageAction;
 
   @JsonKey()
-  final List<String> desiredDeliveryMediums;
+  final List<String>? desiredDeliveryMediums;
 
   @JsonKey()
-  final bool forceAliasCreation;
+  final bool? forceAliasCreation;
 
   @JsonKey()
-  final String smsMessage;
+  final String? smsMessage;
 
   @JsonKey()
-  final String emailMessage;
+  final String? emailMessage;
 
   @JsonKey()
-  final String emailSubject;
+  final String? emailSubject;
 
   const AwsCognitoResponse(
       {this.autoConfirmUser,
@@ -143,16 +144,16 @@ class AwsCognitoResponse {
 @JsonSerializable()
 class AwsGroupConfiguration {
   @JsonKey()
-  final List<String> groupsToOverride;
+  final List<String>? groupsToOverride;
 
   @JsonKey()
-  final List<String> iamRolesToOverride;
+  final List<String>? iamRolesToOverride;
 
   @JsonKey()
-  final String preferredRole;
+  final String? preferredRole;
 
   @JsonKey()
-  final Map<String, String> clientMetadata;
+  final Map<String, String>? clientMetadata;
 
   const AwsGroupConfiguration(
       {this.groupsToOverride,
@@ -169,13 +170,13 @@ class AwsGroupConfiguration {
 @JsonSerializable()
 class AwsClaimOverrideDetails {
   @JsonKey()
-  final Map<String, String> claimsToAddOrOverride;
+  final Map<String, String>? claimsToAddOrOverride;
 
   @JsonKey()
-  final List<String> claimsToSuppress;
+  final List<String>? claimsToSuppress;
 
   @JsonKey()
-  final AwsGroupConfiguration groupOverrideDetails;
+  final AwsGroupConfiguration? groupOverrideDetails;
 
   const AwsClaimOverrideDetails(
       {this.claimsToAddOrOverride,
diff --git a/lib/events/cognito_event.g.dart b/lib/events/cognito_event.g.dart
index 99584150..b3e1e06e 100644
--- a/lib/events/cognito_event.g.dart
+++ b/lib/events/cognito_event.g.dart
@@ -8,12 +8,12 @@ part of 'cognito_event.dart';
 
 AwsCognitoEvent _$AwsCognitoEventFromJson(Map<String, dynamic> json) {
   return AwsCognitoEvent(
-    version: json['version'] as int,
-    triggerSource: json['triggerSource'] as String,
-    region: json['region'] as String,
-    userPoolId: json['userPoolId'] as String,
-    userName: json['userName'] as String,
-    callerContext: (json['callerContext'] as Map<String, dynamic>)?.map(
+    version: json['version'] as int?,
+    triggerSource: json['triggerSource'] as String?,
+    region: json['region'] as String?,
+    userPoolId: json['userPoolId'] as String?,
+    userName: json['userName'] as String?,
+    callerContext: (json['callerContext'] as Map<String, dynamic>?)?.map(
       (k, e) => MapEntry(k, e as String),
     ),
     request: json['request'] == null
@@ -39,16 +39,16 @@ Map<String, dynamic> _$AwsCognitoEventToJson(AwsCognitoEvent instance) =>
 
 AwsCognitoRequest _$AwsCognitoRequestFromJson(Map<String, dynamic> json) {
   return AwsCognitoRequest(
-    userAttributes: json['userAttributes'] as Map<String, dynamic>,
-    validationData: (json['validationData'] as Map<String, dynamic>)?.map(
+    userAttributes: json['userAttributes'] as Map<String, dynamic>?,
+    validationData: (json['validationData'] as Map<String, dynamic>?)?.map(
       (k, e) => MapEntry(k, e as String),
     ),
-    clientMetadata: (json['clientMetadata'] as Map<String, dynamic>)?.map(
+    clientMetadata: (json['clientMetadata'] as Map<String, dynamic>?)?.map(
       (k, e) => MapEntry(k, e as String),
     ),
-    newDeviceUsed: json['newDeviceUsed'] as bool,
-    codeParameter: json['codeParameter'] as String,
-    password: json['password'] as String,
+    newDeviceUsed: json['newDeviceUsed'] as bool?,
+    codeParameter: json['codeParameter'] as String?,
+    password: json['password'] as String?,
     groupConfiguration: json['groupConfiguration'] == null
         ? null
         : AwsGroupConfiguration.fromJson(
@@ -69,25 +69,25 @@ Map<String, dynamic> _$AwsCognitoRequestToJson(AwsCognitoRequest instance) =>
 
 AwsCognitoResponse _$AwsCognitoResponseFromJson(Map<String, dynamic> json) {
   return AwsCognitoResponse(
-    autoConfirmUser: json['autoConfirmUser'] as bool,
-    autoVerifyEmail: json['autoVerifyEmail'] as bool,
-    autoVerifyPhone: json['autoVerifyPhone'] as bool,
+    autoConfirmUser: json['autoConfirmUser'] as bool?,
+    autoVerifyEmail: json['autoVerifyEmail'] as bool?,
+    autoVerifyPhone: json['autoVerifyPhone'] as bool?,
     claimsOverrideDetails: json['claimsOverrideDetails'] == null
         ? null
         : AwsClaimOverrideDetails.fromJson(
             json['claimsOverrideDetails'] as Map<String, dynamic>),
-    userAttributes: (json['userAttributes'] as Map<String, dynamic>)?.map(
+    userAttributes: (json['userAttributes'] as Map<String, dynamic>?)?.map(
       (k, e) => MapEntry(k, e as String),
     ),
-    finalUserStatus: json['finalUserStatus'] as String,
-    desiredDeliveryMediums: (json['desiredDeliveryMediums'] as List)
+    finalUserStatus: json['finalUserStatus'] as String?,
+    desiredDeliveryMediums: (json['desiredDeliveryMediums'] as List<dynamic>?)
         ?.map((e) => e as String)
-        ?.toList(),
-    forceAliasCreation: json['forceAliasCreation'] as bool,
-    messageAction: json['messageAction'] as String,
-    smsMessage: json['smsMessage'] as String,
-    emailMessage: json['emailMessage'] as String,
-    emailSubject: json['emailSubject'] as String,
+        .toList(),
+    forceAliasCreation: json['forceAliasCreation'] as bool?,
+    messageAction: json['messageAction'] as String?,
+    smsMessage: json['smsMessage'] as String?,
+    emailMessage: json['emailMessage'] as String?,
+    emailSubject: json['emailSubject'] as String?,
   );
 }
 
@@ -110,12 +110,14 @@ Map<String, dynamic> _$AwsCognitoResponseToJson(AwsCognitoResponse instance) =>
 AwsGroupConfiguration _$AwsGroupConfigurationFromJson(
     Map<String, dynamic> json) {
   return AwsGroupConfiguration(
-    groupsToOverride:
-        (json['groupsToOverride'] as List)?.map((e) => e as String)?.toList(),
-    iamRolesToOverride:
-        (json['iamRolesToOverride'] as List)?.map((e) => e as String)?.toList(),
-    preferredRole: json['preferredRole'] as String,
-    clientMetadata: (json['clientMetadata'] as Map<String, dynamic>)?.map(
+    groupsToOverride: (json['groupsToOverride'] as List<dynamic>?)
+        ?.map((e) => e as String)
+        .toList(),
+    iamRolesToOverride: (json['iamRolesToOverride'] as List<dynamic>?)
+        ?.map((e) => e as String)
+        .toList(),
+    preferredRole: json['preferredRole'] as String?,
+    clientMetadata: (json['clientMetadata'] as Map<String, dynamic>?)?.map(
       (k, e) => MapEntry(k, e as String),
     ),
   );
@@ -134,11 +136,12 @@ AwsClaimOverrideDetails _$AwsClaimOverrideDetailsFromJson(
     Map<String, dynamic> json) {
   return AwsClaimOverrideDetails(
     claimsToAddOrOverride:
-        (json['claimsToAddOrOverride'] as Map<String, dynamic>)?.map(
+        (json['claimsToAddOrOverride'] as Map<String, dynamic>?)?.map(
       (k, e) => MapEntry(k, e as String),
     ),
-    claimsToSuppress:
-        (json['claimsToSuppress'] as List)?.map((e) => e as String)?.toList(),
+    claimsToSuppress: (json['claimsToSuppress'] as List<dynamic>?)
+        ?.map((e) => e as String)
+        .toList(),
     groupOverrideDetails: json['groupOverrideDetails'] == null
         ? null
         : AwsGroupConfiguration.fromJson(
diff --git a/lib/events/dynamodb_event.dart b/lib/events/dynamodb_event.dart
index 8ca4e06c..3ccf96c7 100644
--- a/lib/events/dynamodb_event.dart
+++ b/lib/events/dynamodb_event.dart
@@ -1,3 +1,4 @@
+import 'package:aws_lambda_dart_runtime/runtime/event.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'dynamodb_event.g.dart';
@@ -5,18 +6,18 @@ part 'dynamodb_event.g.dart';
 /// Event send by a DynamoDB stream that contains
 /// the updated records in the DynamoDB table.
 @JsonSerializable()
-class AwsDynamoDBUpdateRecord {
+class AwsDynamoDBUpdateRecord extends Event {
   /// Keys ...
-  @JsonKey(name: "Keys")
-  final Map<String, dynamic> keys;
+  @JsonKey(name: 'Keys')
+  final Map<String, dynamic>? keys;
 
   /// New Image ...
-  @JsonKey(name: "NewImage")
-  final Map<String, dynamic> oldImage;
+  @JsonKey(name: 'NewImage')
+  final Map<String, dynamic>? oldImage;
 
   /// Old Image ....
-  @JsonKey(name: "OldImage")
-  final Map<String, dynamic> newImage;
+  @JsonKey(name: 'OldImage')
+  final Map<String, dynamic>? newImage;
 
   factory AwsDynamoDBUpdateRecord.fromJson(Map<String, dynamic> json) =>
       _$AwsDynamoDBUpdateRecordFromJson(json);
@@ -31,27 +32,27 @@ class AwsDynamoDBUpdateRecord {
 class AwsDynamoDBUpdateEventRecord {
   /// Event Id ...
   @JsonKey()
-  final String eventId;
+  final String? eventId;
 
   /// Event Name ...
   @JsonKey()
-  final String eventName;
+  final String? eventName;
 
   /// Event Source ...
   @JsonKey()
-  final String eventSource;
+  final String? eventSource;
 
   /// Event Version ...
   @JsonKey()
-  final String eventVersion;
+  final String? eventVersion;
 
   /// AWS Region ...
   @JsonKey()
-  final String awsRegion;
+  final String? awsRegion;
 
   /// Event Source ARN ...
   @JsonKey()
-  final String eventSourceARN;
+  final String? eventSourceARN;
 
   factory AwsDynamoDBUpdateEventRecord.fromJson(Map<String, dynamic> json) =>
       _$AwsDynamoDBUpdateEventRecordFromJson(json);
@@ -69,10 +70,10 @@ class AwsDynamoDBUpdateEventRecord {
 
 /// DynamoDB Update Event ...
 @JsonSerializable()
-class AwsDynamoDBUpdateEvent {
+class AwsDynamoDBUpdateEvent extends Event {
   /// awslogs ...
-  @JsonKey(name: "Records")
-  final List<AwsDynamoDBUpdateEventRecord> records;
+  @JsonKey(name: 'Records')
+  final List<AwsDynamoDBUpdateEventRecord>? records;
 
   factory AwsDynamoDBUpdateEvent.fromJson(Map<String, dynamic> json) =>
       _$AwsDynamoDBUpdateEventFromJson(json);
diff --git a/lib/events/dynamodb_event.g.dart b/lib/events/dynamodb_event.g.dart
index 82de5627..92d497a0 100644
--- a/lib/events/dynamodb_event.g.dart
+++ b/lib/events/dynamodb_event.g.dart
@@ -9,9 +9,9 @@ part of 'dynamodb_event.dart';
 AwsDynamoDBUpdateRecord _$AwsDynamoDBUpdateRecordFromJson(
     Map<String, dynamic> json) {
   return AwsDynamoDBUpdateRecord(
-    keys: json['Keys'] as Map<String, dynamic>,
-    oldImage: json['NewImage'] as Map<String, dynamic>,
-    newImage: json['OldImage'] as Map<String, dynamic>,
+    keys: json['Keys'] as Map<String, dynamic>?,
+    oldImage: json['NewImage'] as Map<String, dynamic>?,
+    newImage: json['OldImage'] as Map<String, dynamic>?,
   );
 }
 
@@ -26,12 +26,12 @@ Map<String, dynamic> _$AwsDynamoDBUpdateRecordToJson(
 AwsDynamoDBUpdateEventRecord _$AwsDynamoDBUpdateEventRecordFromJson(
     Map<String, dynamic> json) {
   return AwsDynamoDBUpdateEventRecord(
-    eventId: json['eventId'] as String,
-    eventName: json['eventName'] as String,
-    eventSource: json['eventSource'] as String,
-    eventVersion: json['eventVersion'] as String,
-    awsRegion: json['awsRegion'] as String,
-    eventSourceARN: json['eventSourceARN'] as String,
+    eventId: json['eventId'] as String?,
+    eventName: json['eventName'] as String?,
+    eventSource: json['eventSource'] as String?,
+    eventVersion: json['eventVersion'] as String?,
+    awsRegion: json['awsRegion'] as String?,
+    eventSourceARN: json['eventSourceARN'] as String?,
   );
 }
 
@@ -49,11 +49,10 @@ Map<String, dynamic> _$AwsDynamoDBUpdateEventRecordToJson(
 AwsDynamoDBUpdateEvent _$AwsDynamoDBUpdateEventFromJson(
     Map<String, dynamic> json) {
   return AwsDynamoDBUpdateEvent(
-    records: (json['Records'] as List)
-        ?.map((e) => e == null
-            ? null
-            : AwsDynamoDBUpdateEventRecord.fromJson(e as Map<String, dynamic>))
-        ?.toList(),
+    records: (json['Records'] as List<dynamic>?)
+        ?.map((e) =>
+            AwsDynamoDBUpdateEventRecord.fromJson(e as Map<String, dynamic>))
+        .toList(),
   );
 }
 
diff --git a/lib/events/kinesis_data_firehose_event.dart b/lib/events/kinesis_data_firehose_event.dart
index fcfd8fdb..bea0ed0c 100644
--- a/lib/events/kinesis_data_firehose_event.dart
+++ b/lib/events/kinesis_data_firehose_event.dart
@@ -1,21 +1,22 @@
+import 'package:aws_lambda_dart_runtime/runtime/event.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'kinesis_data_firehose_event.g.dart';
 
 /// Kinesis .....
 @JsonSerializable()
-class AwsKinesisFirehoseData {
+class AwsKinesisFirehoseData extends Event {
   /// Record ID ...
   @JsonKey()
-  final String recordId;
+  final String? recordId;
 
   /// Approximated Arrival Timestamp ...
   @JsonKey()
-  final int approximateArrivalTimestamp;
+  final int? approximateArrivalTimestamp;
 
   /// Data ...
   @JsonKey()
-  final String data;
+  final String? data;
 
   factory AwsKinesisFirehoseData.fromJson(Map<String, dynamic> json) {
     return _$AwsKinesisFirehoseDataFromJson(json);
@@ -32,19 +33,19 @@ class AwsKinesisFirehoseData {
 class AwsKinesisFirehoseDataEvent {
   /// Invocation ID ...
   @JsonKey()
-  final String invocationId;
+  final String? invocationId;
 
   /// Delivery Stream ARN ...
   @JsonKey()
-  final String deliveryStreamArn;
+  final String? deliveryStreamArn;
 
   /// Region ...
   @JsonKey()
-  final String region;
+  final String? region;
 
   /// Records ...
   @JsonKey()
-  final List<AwsKinesisFirehoseData> records;
+  final List<AwsKinesisFirehoseData>? records;
 
   factory AwsKinesisFirehoseDataEvent.fromJson(Map<String, dynamic> json) {
     return _$AwsKinesisFirehoseDataEventFromJson(json);
diff --git a/lib/events/kinesis_data_firehose_event.g.dart b/lib/events/kinesis_data_firehose_event.g.dart
index 7785f615..028b9446 100644
--- a/lib/events/kinesis_data_firehose_event.g.dart
+++ b/lib/events/kinesis_data_firehose_event.g.dart
@@ -9,9 +9,9 @@ part of 'kinesis_data_firehose_event.dart';
 AwsKinesisFirehoseData _$AwsKinesisFirehoseDataFromJson(
     Map<String, dynamic> json) {
   return AwsKinesisFirehoseData(
-    recordId: json['recordId'] as String,
-    data: json['data'] as String,
-    approximateArrivalTimestamp: json['approximateArrivalTimestamp'] as int,
+    recordId: json['recordId'] as String?,
+    data: json['data'] as String?,
+    approximateArrivalTimestamp: json['approximateArrivalTimestamp'] as int?,
   );
 }
 
@@ -26,14 +26,12 @@ Map<String, dynamic> _$AwsKinesisFirehoseDataToJson(
 AwsKinesisFirehoseDataEvent _$AwsKinesisFirehoseDataEventFromJson(
     Map<String, dynamic> json) {
   return AwsKinesisFirehoseDataEvent(
-    records: (json['records'] as List)
-        ?.map((e) => e == null
-            ? null
-            : AwsKinesisFirehoseData.fromJson(e as Map<String, dynamic>))
-        ?.toList(),
-    invocationId: json['invocationId'] as String,
-    deliveryStreamArn: json['deliveryStreamArn'] as String,
-    region: json['region'] as String,
+    records: (json['records'] as List<dynamic>?)
+        ?.map((e) => AwsKinesisFirehoseData.fromJson(e as Map<String, dynamic>))
+        .toList(),
+    invocationId: json['invocationId'] as String?,
+    deliveryStreamArn: json['deliveryStreamArn'] as String?,
+    region: json['region'] as String?,
   );
 }
 
diff --git a/lib/events/kinesis_data_stream_event.dart b/lib/events/kinesis_data_stream_event.dart
index c83a0865..a3ea4b78 100644
--- a/lib/events/kinesis_data_stream_event.dart
+++ b/lib/events/kinesis_data_stream_event.dart
@@ -1,29 +1,30 @@
+import 'package:aws_lambda_dart_runtime/runtime/event.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'kinesis_data_stream_event.g.dart';
 
 /// Kinesis .....
 @JsonSerializable()
-class AwsKinesisDataStream {
+class AwsKinesisDataStream extends Event {
   /// Partition Key ...
   @JsonKey()
-  final String partitionKey;
+  final String? partitionKey;
 
   /// Kinesis Schema Version ...
   @JsonKey()
-  final String kinesisSchemaVersion;
+  final String? kinesisSchemaVersion;
 
   /// Data ...
   @JsonKey()
-  final String data;
+  final String? data;
 
   /// Sequenzer Number ...
   @JsonKey()
-  final String sequenceNumber;
+  final String? sequenceNumber;
 
   /// Approximate Arrival Timestamp ...
   @JsonKey()
-  final int approximateArrivalTimestamp;
+  final int? approximateArrivalTimestamp;
 
   factory AwsKinesisDataStream.fromJson(Map<String, dynamic> json) {
     return _$AwsKinesisDataStreamFromJson(json);
@@ -44,35 +45,35 @@ class AwsKinesisDataStream {
 class AwsKinesisDataStreamRecord {
   /// Data ...
   @JsonKey()
-  final AwsKinesisDataStream kinesis;
+  final AwsKinesisDataStream? kinesis;
 
   /// Source of the Event.
   @JsonKey()
-  final String eventSource;
+  final String? eventSource;
 
   /// Event Id ...
   @JsonKey()
-  final String eventID;
+  final String? eventID;
 
   /// Event Version ...
   @JsonKey()
-  final String eventVersion;
+  final String? eventVersion;
 
   /// Event Name ...
   @JsonKey()
-  final String eventName;
+  final String? eventName;
 
   /// Event Source ARN ...
   @JsonKey()
-  final String eventSourceARN;
+  final String? eventSourceARN;
 
   /// Invokey Identity ARN ...
   @JsonKey()
-  final String invokeIdentityArn;
+  final String? invokeIdentityArn;
 
   /// Aws Region this event was emitted from
   @JsonKey()
-  final String awsRegion;
+  final String? awsRegion;
 
   factory AwsKinesisDataStreamRecord.fromJson(Map<String, dynamic> json) {
     return _$AwsKinesisDataStreamRecordFromJson(json);
@@ -93,10 +94,10 @@ class AwsKinesisDataStreamRecord {
 
 /// Kinesis Event ...
 @JsonSerializable()
-class AwsKinesisDataStreamEvent {
+class AwsKinesisDataStreamEvent extends Event {
   /// The SQS message records that have been send with the event.
-  @JsonKey(name: "Records")
-  final List<AwsKinesisDataStreamRecord> records;
+  @JsonKey(name: 'Records')
+  final List<AwsKinesisDataStreamRecord>? records;
 
   factory AwsKinesisDataStreamEvent.fromJson(Map<String, dynamic> json) {
     return _$AwsKinesisDataStreamEventFromJson(json);
diff --git a/lib/events/kinesis_data_stream_event.g.dart b/lib/events/kinesis_data_stream_event.g.dart
index 8bfd3cb6..c1bbf2ac 100644
--- a/lib/events/kinesis_data_stream_event.g.dart
+++ b/lib/events/kinesis_data_stream_event.g.dart
@@ -8,11 +8,11 @@ part of 'kinesis_data_stream_event.dart';
 
 AwsKinesisDataStream _$AwsKinesisDataStreamFromJson(Map<String, dynamic> json) {
   return AwsKinesisDataStream(
-    partitionKey: json['partitionKey'] as String,
-    kinesisSchemaVersion: json['kinesisSchemaVersion'] as String,
-    data: json['data'] as String,
-    sequenceNumber: json['sequenceNumber'] as String,
-    approximateArrivalTimestamp: json['approximateArrivalTimestamp'] as int,
+    partitionKey: json['partitionKey'] as String?,
+    kinesisSchemaVersion: json['kinesisSchemaVersion'] as String?,
+    data: json['data'] as String?,
+    sequenceNumber: json['sequenceNumber'] as String?,
+    approximateArrivalTimestamp: json['approximateArrivalTimestamp'] as int?,
   );
 }
 
@@ -33,13 +33,13 @@ AwsKinesisDataStreamRecord _$AwsKinesisDataStreamRecordFromJson(
         ? null
         : AwsKinesisDataStream.fromJson(
             json['kinesis'] as Map<String, dynamic>),
-    invokeIdentityArn: json['invokeIdentityArn'] as String,
-    eventName: json['eventName'] as String,
-    eventID: json['eventID'] as String,
-    eventSource: json['eventSource'] as String,
-    eventVersion: json['eventVersion'] as String,
-    eventSourceARN: json['eventSourceARN'] as String,
-    awsRegion: json['awsRegion'] as String,
+    invokeIdentityArn: json['invokeIdentityArn'] as String?,
+    eventName: json['eventName'] as String?,
+    eventID: json['eventID'] as String?,
+    eventSource: json['eventSource'] as String?,
+    eventVersion: json['eventVersion'] as String?,
+    eventSourceARN: json['eventSourceARN'] as String?,
+    awsRegion: json['awsRegion'] as String?,
   );
 }
 
@@ -59,11 +59,10 @@ Map<String, dynamic> _$AwsKinesisDataStreamRecordToJson(
 AwsKinesisDataStreamEvent _$AwsKinesisDataStreamEventFromJson(
     Map<String, dynamic> json) {
   return AwsKinesisDataStreamEvent(
-    records: (json['Records'] as List)
-        ?.map((e) => e == null
-            ? null
-            : AwsKinesisDataStreamRecord.fromJson(e as Map<String, dynamic>))
-        ?.toList(),
+    records: (json['Records'] as List<dynamic>?)
+        ?.map((e) =>
+            AwsKinesisDataStreamRecord.fromJson(e as Map<String, dynamic>))
+        .toList(),
   );
 }
 
diff --git a/lib/events/s3_event.dart b/lib/events/s3_event.dart
index 26af55bf..67eede36 100644
--- a/lib/events/s3_event.dart
+++ b/lib/events/s3_event.dart
@@ -1,3 +1,4 @@
+import 'package:aws_lambda_dart_runtime/runtime/event.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 's3_event.g.dart';
@@ -5,9 +6,9 @@ part 's3_event.g.dart';
 /// Representing a recorded S3 Event send to the Lambda.
 /// This can be send in batches of operations.
 @JsonSerializable()
-class AwsS3Event {
-  @JsonKey(name: "Records")
-  final List<AwsS3EventRecord> records;
+class AwsS3Event extends Event {
+  @JsonKey(name: 'Records')
+  final List<AwsS3EventRecord>? records;
 
   const AwsS3Event({this.records});
 
@@ -20,15 +21,15 @@ class AwsS3Event {
 /// Notifcation Event for Lambda in S3.
 @JsonSerializable()
 class AwsS3EventRecord {
-  final String eventVersion;
-  final String eventSource;
-  final String awsRegion;
-  final DateTime eventTime;
-  final String eventName;
-  final AwsS3UserIdentity userIdentity;
-  final Map<String, String> requestParameters;
-  final Map<String, String> responseElements;
-  final AwsS3Data s3;
+  final String? eventVersion;
+  final String? eventSource;
+  final String? awsRegion;
+  final DateTime? eventTime;
+  final String? eventName;
+  final AwsS3UserIdentity? userIdentity;
+  final Map<String, String>? requestParameters;
+  final Map<String, String>? responseElements;
+  final AwsS3Data? s3;
 
   const AwsS3EventRecord(
       {this.eventName,
@@ -49,10 +50,10 @@ class AwsS3EventRecord {
 
 @JsonSerializable()
 class AwsS3Data {
-  String s3SchemaVersion;
-  String configurationId;
-  AwsS3Bucket bucket;
-  AWSS3EventObject object;
+  String? s3SchemaVersion;
+  String? configurationId;
+  AwsS3Bucket? bucket;
+  AWSS3EventObject? object;
 
   AwsS3Data(
       {this.s3SchemaVersion, this.configurationId, this.bucket, this.object});
@@ -65,9 +66,9 @@ class AwsS3Data {
 
 @JsonSerializable()
 class AwsS3Bucket {
-  String name;
-  AwsS3UserIdentity ownerIdentity;
-  String arn;
+  String? name;
+  AwsS3UserIdentity? ownerIdentity;
+  String? arn;
 
   AwsS3Bucket({this.name, this.ownerIdentity, this.arn});
 
@@ -79,10 +80,10 @@ class AwsS3Bucket {
 
 @JsonSerializable()
 class AWSS3EventObject {
-  String key;
-  int size;
-  String eTag;
-  String sequencer;
+  String? key;
+  int? size;
+  String? eTag;
+  String? sequencer;
 
   AWSS3EventObject({this.key, this.size, this.eTag, this.sequencer});
 
@@ -94,7 +95,7 @@ class AWSS3EventObject {
 
 @JsonSerializable()
 class AwsS3UserIdentity {
-  String principalId;
+  String? principalId;
 
   AwsS3UserIdentity({this.principalId});
 
diff --git a/lib/events/s3_event.g.dart b/lib/events/s3_event.g.dart
index 6654fdf8..a8a36df5 100644
--- a/lib/events/s3_event.g.dart
+++ b/lib/events/s3_event.g.dart
@@ -8,11 +8,9 @@ part of 's3_event.dart';
 
 AwsS3Event _$AwsS3EventFromJson(Map<String, dynamic> json) {
   return AwsS3Event(
-    records: (json['Records'] as List)
-        ?.map((e) => e == null
-            ? null
-            : AwsS3EventRecord.fromJson(e as Map<String, dynamic>))
-        ?.toList(),
+    records: (json['Records'] as List<dynamic>?)
+        ?.map((e) => AwsS3EventRecord.fromJson(e as Map<String, dynamic>))
+        .toList(),
   );
 }
 
@@ -23,21 +21,22 @@ Map<String, dynamic> _$AwsS3EventToJson(AwsS3Event instance) =>
 
 AwsS3EventRecord _$AwsS3EventRecordFromJson(Map<String, dynamic> json) {
   return AwsS3EventRecord(
-    eventName: json['eventName'] as String,
-    eventSource: json['eventSource'] as String,
-    awsRegion: json['awsRegion'] as String,
+    eventName: json['eventName'] as String?,
+    eventSource: json['eventSource'] as String?,
+    awsRegion: json['awsRegion'] as String?,
     eventTime: json['eventTime'] == null
         ? null
         : DateTime.parse(json['eventTime'] as String),
-    eventVersion: json['eventVersion'] as String,
+    eventVersion: json['eventVersion'] as String?,
     userIdentity: json['userIdentity'] == null
         ? null
         : AwsS3UserIdentity.fromJson(
             json['userIdentity'] as Map<String, dynamic>),
-    requestParameters: (json['requestParameters'] as Map<String, dynamic>)?.map(
+    requestParameters:
+        (json['requestParameters'] as Map<String, dynamic>?)?.map(
       (k, e) => MapEntry(k, e as String),
     ),
-    responseElements: (json['responseElements'] as Map<String, dynamic>)?.map(
+    responseElements: (json['responseElements'] as Map<String, dynamic>?)?.map(
       (k, e) => MapEntry(k, e as String),
     ),
     s3: json['s3'] == null
@@ -61,8 +60,8 @@ Map<String, dynamic> _$AwsS3EventRecordToJson(AwsS3EventRecord instance) =>
 
 AwsS3Data _$AwsS3DataFromJson(Map<String, dynamic> json) {
   return AwsS3Data(
-    s3SchemaVersion: json['s3SchemaVersion'] as String,
-    configurationId: json['configurationId'] as String,
+    s3SchemaVersion: json['s3SchemaVersion'] as String?,
+    configurationId: json['configurationId'] as String?,
     bucket: json['bucket'] == null
         ? null
         : AwsS3Bucket.fromJson(json['bucket'] as Map<String, dynamic>),
@@ -81,12 +80,12 @@ Map<String, dynamic> _$AwsS3DataToJson(AwsS3Data instance) => <String, dynamic>{
 
 AwsS3Bucket _$AwsS3BucketFromJson(Map<String, dynamic> json) {
   return AwsS3Bucket(
-    name: json['name'] as String,
+    name: json['name'] as String?,
     ownerIdentity: json['ownerIdentity'] == null
         ? null
         : AwsS3UserIdentity.fromJson(
             json['ownerIdentity'] as Map<String, dynamic>),
-    arn: json['arn'] as String,
+    arn: json['arn'] as String?,
   );
 }
 
@@ -99,10 +98,10 @@ Map<String, dynamic> _$AwsS3BucketToJson(AwsS3Bucket instance) =>
 
 AWSS3EventObject _$AWSS3EventObjectFromJson(Map<String, dynamic> json) {
   return AWSS3EventObject(
-    key: json['key'] as String,
-    size: json['size'] as int,
-    eTag: json['eTag'] as String,
-    sequencer: json['sequencer'] as String,
+    key: json['key'] as String?,
+    size: json['size'] as int?,
+    eTag: json['eTag'] as String?,
+    sequencer: json['sequencer'] as String?,
   );
 }
 
@@ -116,7 +115,7 @@ Map<String, dynamic> _$AWSS3EventObjectToJson(AWSS3EventObject instance) =>
 
 AwsS3UserIdentity _$AwsS3UserIdentityFromJson(Map<String, dynamic> json) {
   return AwsS3UserIdentity(
-    principalId: json['principalId'] as String,
+    principalId: json['principalId'] as String?,
   );
 }
 
diff --git a/lib/events/sqs_event.dart b/lib/events/sqs_event.dart
index b3cc57c8..21c6acdc 100644
--- a/lib/events/sqs_event.dart
+++ b/lib/events/sqs_event.dart
@@ -1,45 +1,46 @@
+import 'package:aws_lambda_dart_runtime/runtime/event.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'sqs_event.g.dart';
 
 /// SQS Event Record that is send via [AwsSQSEvent].
 @JsonSerializable()
-class AwsSQSEventRecord {
+class AwsSQSEventRecord extends Event {
   /// Id of the SQS message.
   @JsonKey()
-  final String messageId;
+  final String? messageId;
 
   /// Name of the receipt handle.
   @JsonKey()
-  final String receiptHandle;
+  final String? receiptHandle;
 
   /// Body of the message
   @JsonKey()
-  final String body;
+  final String? body;
 
   /// Attributes that are send with the event.
   @JsonKey()
-  final Map<String, dynamic> attributes;
+  final Map<String, dynamic>? attributes;
 
   /// Message attributes that are send with the event.
   @JsonKey()
-  final Map<String, dynamic> messageAttributes;
+  final Map<String, dynamic>? messageAttributes;
 
   /// The md5 hash of the message body.
   @JsonKey()
-  final String md5OfBody;
+  final String? md5OfBody;
 
   /// Source of the Event.
   @JsonKey()
-  final String eventSource;
+  final String? eventSource;
 
   /// Source of the Event ARN.
   @JsonKey()
-  final String eventSourceARN;
+  final String? eventSourceARN;
 
   /// Aws Region this event was emitted from
   @JsonKey()
-  final String awsRegion;
+  final String? awsRegion;
 
   factory AwsSQSEventRecord.fromJson(Map<String, dynamic> json) {
     return _$AwsSQSEventRecordFromJson(json);
@@ -62,10 +63,10 @@ class AwsSQSEventRecord {
 /// Event that is send via SQS to trigger for an innovation
 /// of a Lambda.
 @JsonSerializable()
-class AwsSQSEvent {
+class AwsSQSEvent extends Event {
   /// The SQS message records that have been send with the event.
-  @JsonKey(name: "Records")
-  final List<AwsSQSEventRecord> records;
+  @JsonKey(name: 'Records')
+  final List<AwsSQSEventRecord>? records;
 
   factory AwsSQSEvent.fromJson(Map<String, dynamic> json) {
     return _$AwsSQSEventFromJson(json);
diff --git a/lib/events/sqs_event.g.dart b/lib/events/sqs_event.g.dart
index df3b983f..ac257207 100644
--- a/lib/events/sqs_event.g.dart
+++ b/lib/events/sqs_event.g.dart
@@ -8,15 +8,15 @@ part of 'sqs_event.dart';
 
 AwsSQSEventRecord _$AwsSQSEventRecordFromJson(Map<String, dynamic> json) {
   return AwsSQSEventRecord(
-    messageId: json['messageId'] as String,
-    body: json['body'] as String,
-    receiptHandle: json['receiptHandle'] as String,
-    attributes: json['attributes'] as Map<String, dynamic>,
-    messageAttributes: json['messageAttributes'] as Map<String, dynamic>,
-    md5OfBody: json['md5OfBody'] as String,
-    eventSource: json['eventSource'] as String,
-    eventSourceARN: json['eventSourceARN'] as String,
-    awsRegion: json['awsRegion'] as String,
+    messageId: json['messageId'] as String?,
+    body: json['body'] as String?,
+    receiptHandle: json['receiptHandle'] as String?,
+    attributes: json['attributes'] as Map<String, dynamic>?,
+    messageAttributes: json['messageAttributes'] as Map<String, dynamic>?,
+    md5OfBody: json['md5OfBody'] as String?,
+    eventSource: json['eventSource'] as String?,
+    eventSourceARN: json['eventSourceARN'] as String?,
+    awsRegion: json['awsRegion'] as String?,
   );
 }
 
@@ -35,11 +35,9 @@ Map<String, dynamic> _$AwsSQSEventRecordToJson(AwsSQSEventRecord instance) =>
 
 AwsSQSEvent _$AwsSQSEventFromJson(Map<String, dynamic> json) {
   return AwsSQSEvent(
-    records: (json['Records'] as List)
-        ?.map((e) => e == null
-            ? null
-            : AwsSQSEventRecord.fromJson(e as Map<String, dynamic>))
-        ?.toList(),
+    records: (json['Records'] as List<dynamic>?)
+        ?.map((e) => AwsSQSEventRecord.fromJson(e as Map<String, dynamic>))
+        .toList(),
   );
 }
 
diff --git a/lib/runtime/context.dart b/lib/runtime/context.dart
index 231eaafb..2bfe5801 100644
--- a/lib/runtime/context.dart
+++ b/lib/runtime/context.dart
@@ -1,4 +1,5 @@
 import 'dart:io' show Platform;
+
 import '../client/client.dart';
 
 /// Context contains the Lambda execution context information.
@@ -24,72 +25,74 @@ class Context {
 
   /// Creates a new [Context] from [NextInvocation] which is the data
   /// from the Lambda Runtime Interface for the next [Handler<T>] invocation.
-  static fromNextInvocation(NextInvocation nextInvocation) {
+  static Context fromNextInvocation(NextInvocation nextInvocation) {
     return Context(
-        requestId: nextInvocation.requestId,
-        invokedFunction: nextInvocation.invokedFunctionArn);
+      handler: Client.handlerName!,
+      requestId: nextInvocation.requestId,
+      invokedFunction: nextInvocation.invokedFunctionArn,
+    );
   }
 
   /// Handler that is used for the invocation of the function
-  String handler;
+  String? handler;
 
   /// Name of the function that is invoked.
-  String functionName;
+  String? functionName;
 
   /// Version of the function that is invoked.
-  String functionVersion;
+  String? functionVersion;
 
   /// Memory sized that is allocated to execution of the function.
-  String functionMemorySize;
+  String? functionMemorySize;
 
   /// Cloudwatch LogGroup that is associated with the Lambda.
-  String logGroupName;
+  String? logGroupName;
 
   /// Cloudwach LogStream that is associated with the Lambda.
-  String logStreamName;
+  String? logStreamName;
 
   /// Region that this function exists in.
-  String region;
+  String? region;
 
   /// The execution environment of the function.
-  String executionEnv;
+  String? executionEnv;
 
   /// Access key that is acquired via STS.
-  String accessKey;
+  String? accessKey;
 
   /// Secret access key that is acquired via STS.
-  String secretAccessKey;
+  String? secretAccessKey;
 
   /// The session token from STS.
-  String sessionToken;
+  String? sessionToken;
 
   /// Id of the request.
   /// You can use this to track the request for the invocation.
-  String requestId;
+  String? requestId;
 
   /// The ARN to identify the function.
-  String invokedFunctionArn;
-
-  Context(
-      {String handler,
-      String functionName,
-      String functionMemorySize,
-      String logGroupName,
-      String logStreamName,
-      String requestId,
-      String invokedFunction,
-      String region,
-      String executionEnv,
-      String accessKey,
-      String secretAccessKey,
-      String sessionToken}) {
-    assert(requestId != null);
+  String? invokedFunctionArn;
+
+  Context({
+    String? handler,
+    String? functionName,
+    String? functionMemorySize,
+    String? logGroupName,
+    String? logStreamName,
+    required String requestId,
+    String? invokedFunction,
+    String? region,
+    String? executionEnv,
+    String? accessKey,
+    String? secretAccessKey,
+    String? sessionToken,
+  }) {
     assert(handler != null);
 
     this.handler = handler ?? Platform.environment[_kAWSLambdaHandler];
     this.functionName =
         functionName ?? Platform.environment[_kAWSLambdaFunctionName];
-    this.functionVersion =
+    functionVersion =
         functionVersion ?? Platform.environment[_kAWSLambdaFunctionVersion];
     this.functionMemorySize = functionMemorySize ??
         Platform.environment[_kAWSLambdaFunctionMemorySize];
@@ -98,7 +101,7 @@ class Context {
     this.logStreamName =
         logStreamName ?? Platform.environment[_kAWSLambdaLogStreamName];
     this.requestId = requestId;
-    this.invokedFunctionArn = invokedFunctionArn;
+    invokedFunctionArn = invokedFunction;
     this.region = region ?? Platform.environment[_kAWSLambdaRegion];
     this.executionEnv =
         executionEnv ?? Platform.environment[_kAWSLambdaExecutionEnv];
@@ -110,27 +113,28 @@ class Context {
   }
 
   /// Allows to copy a created [Context] over with some new settings.
-  Context copyWith(
-      {String handler,
-      String functionName,
-      String functionMemorySize,
-      String logGroupName,
-      String logStreamName,
-      String requestId,
-      String invokedFunction,
-      String region,
-      String executionEnv,
-      String accessKey,
-      String secretAccessKey,
-      String sessionToken}) {
+  Context copyWith({
+    String? handler,
+    String? functionName,
+    String? functionMemorySize,
+    String? logGroupName,
+    String? logStreamName,
+    String? requestId,
+    String? invokedFunction,
+    String? region,
+    String? executionEnv,
+    String? accessKey,
+    String? secretAccessKey,
+    String? sessionToken,
+  }) {
     return Context(
-        handler: handler ?? this.handler,
+        handler: handler ?? this.handler!,
         functionName: functionName ?? this.functionName,
         functionMemorySize: functionMemorySize ?? this.functionMemorySize,
         logGroupName: logGroupName ?? this.logGroupName,
         logStreamName: logStreamName ?? this.logStreamName,
-        requestId: requestId ?? this.requestId,
-        invokedFunction: invokedFunction ?? this.invokedFunctionArn,
+        requestId: requestId ?? this.requestId!,
+        invokedFunction: invokedFunction ?? invokedFunctionArn,
         region: region ?? this.region,
         executionEnv: executionEnv ?? this.executionEnv,
         accessKey: accessKey ?? this.accessKey,
diff --git a/lib/runtime/event.dart b/lib/runtime/event.dart
index 3802e2cb..47ee9831 100644
--- a/lib/runtime/event.dart
+++ b/lib/runtime/event.dart
@@ -1,3 +1,5 @@
+import 'package:aws_lambda_dart_runtime/aws_lambda_dart_runtime.dart';
+
 import '../events/alb_event.dart';
 import '../events/alexa_event.dart';
 import '../events/apigateway_event.dart';
@@ -16,50 +18,47 @@ import '../events/kinesis_data_stream_event.dart';
 /// Note is currently not supported to register your
 /// own events here.
 abstract class Event {
-  static final _registry = {
-    AwsCognitoEvent: (Map<String, dynamic> json) =>
-        AwsCognitoEvent.fromJson(json),
-    AwsS3Event: (Map<String, dynamic> json) => AwsS3Event.fromJson(json),
-    AwsApiGatewayEvent: (Map<String, dynamic> json) =>
-        AwsApiGatewayEvent.fromJson(json),
-    AwsAppSyncEvent: (Map<String, dynamic> json) =>
-        AwsAppSyncEvent.fromJson(json),
-    AwsALBEvent: (Map<String, dynamic> json) => AwsALBEvent.fromJson(json),
-    AwsAlexaEvent: (Map<String, dynamic> json) => AwsAlexaEvent.fromJson(json),
-    AwsSQSEvent: (Map<String, dynamic> json) => AwsSQSEvent.fromJson(json),
-    AwsCloudwatchEvent: (Map<String, dynamic> json) =>
-        AwsCloudwatchEvent.fromJson(json),
-    AwsCloudwatchLogEvent: (Map<String, dynamic> json) =>
-        AwsCloudwatchLogEvent.fromJson(json),
-    AwsDynamoDBUpdateEvent: (Map<String, dynamic> json) =>
-        AwsDynamoDBUpdateEvent.fromJson(json),
-    AwsKinesisDataStreamEvent: (Map<String, dynamic> json) =>
-        AwsKinesisDataStreamEvent.fromJson(json)
+  const Event();
+  static final Map<Type, Function(Map<String, dynamic>)> _registry = {
+    AwsCognitoEvent: (Map<String, dynamic>? json) =>
+        AwsCognitoEvent.fromJson(json!),
+    AwsS3Event: (Map<String, dynamic>? json) => AwsS3Event.fromJson(json!),
+    AwsApiGatewayEvent: (Map<String, dynamic>? json) =>
+        AwsApiGatewayEvent.fromJson(json!),
+    AwsAppSyncEvent: (Map<String, dynamic>? json) =>
+        AwsAppSyncEvent.fromJson(json!),
+    AwsALBEvent: (Map<String, dynamic>? json) => AwsALBEvent.fromJson(json!),
+    AwsAlexaEvent: (Map<String, dynamic>? json) =>
+        AwsAlexaEvent.fromJson(json!),
+    AwsSQSEvent: (Map<String, dynamic>? json) => AwsSQSEvent.fromJson(json!),
+    AwsCloudwatchEvent: (Map<String, dynamic>? json) =>
+        AwsCloudwatchEvent.fromJson(json!),
+    AwsCloudwatchLogEvent: (Map<String, dynamic>? json) =>
+        AwsCloudwatchLogEvent.fromJson(json!),
+    AwsDynamoDBUpdateEvent: (Map<String, dynamic>? json) =>
+        AwsDynamoDBUpdateEvent.fromJson(json!),
+    AwsKinesisDataStreamEvent: (Map<String, dynamic>? json) =>
+        AwsKinesisDataStreamEvent.fromJson(json!)
   };
 
   /// Checks if a type of event is already registered.
-  static exists<T>() {
+  static bool exists<T>() {
     return Event._registry.containsKey(T);
   }
 
   /// Returs the value of a registered event. It is [null]
   /// if no such event has been registered.
-  static value<T>() {
-    return Event._registry[T];
-  }
+  static T Function(Map<String, dynamic>)? value<T extends Event>() =>
+      Event._registry[T] as T Function(Map<String, dynamic>)?;
 
   /// Registers an event.
-  static registerEvent<T>(func) {
-    Event._registry[T] = func;
-  }
+  static void registerEvent<T>(T Function(Map<String, dynamic>) func) =>
+      Event._registry[T] = func;
 
   /// Deregisters an event.
-  static deregisterEvent<T>() {
-    Event._registry.remove(T);
-  }
+  static void deregisterEvent<T>() => Event._registry.remove(T);
 
   /// Creates a new event from a handler type with the [NextInvocation.response].
-  static fromHandler<T>(Type type, Map<String, dynamic> json) {
-    return _registry[type](json);
-  }
+  static dynamic fromHandler<T>(Type type, Map<String, dynamic> json) =>
+      _registry[type]!(json);
 }
diff --git a/lib/runtime/exception.dart b/lib/runtime/exception.dart
index b655b0ad..b774f1e1 100644
--- a/lib/runtime/exception.dart
+++ b/lib/runtime/exception.dart
@@ -7,5 +7,5 @@ class RuntimeException implements Exception {
   final String cause;
 
   @override
-  String toString() => "RuntimeException: $cause";
+  String toString() => 'RuntimeException: $cause';
 }
diff --git a/lib/runtime/runtime.dart b/lib/runtime/runtime.dart
index 106d7474..06a929f7 100644
--- a/lib/runtime/runtime.dart
+++ b/lib/runtime/runtime.dart
@@ -1,23 +1,22 @@
 import 'dart:async';
 
-import '../client/client.dart';
-import 'event.dart';
-import 'context.dart';
-import 'exception.dart';
+import 'package:aws_lambda_dart_runtime/aws_lambda_dart_runtime.dart';
+
+import 'package:aws_lambda_dart_runtime/client/client.dart';
+import 'package:aws_lambda_dart_runtime/runtime/event.dart';
+import 'package:aws_lambda_dart_runtime/runtime/context.dart';
+import 'package:aws_lambda_dart_runtime/runtime/exception.dart';
 
 /// A function which ingests and Event and a [Context]
 /// and returns a [InvocationResult]. The result is ecoded
 /// by the [Runtime] and posted to the Lambda API.
-typedef Handler<T> = Future<InvocationResult> Function(
-    Context context, T event);
+typedef Handler<E> = Future Function(Context context, E event);
 
 class _RuntimeHandler {
   final Type type;
   final dynamic handler;
 
-  const _RuntimeHandler(this.type, this.handler)
-      : assert(type != null),
-        assert(handler != null);
+  const _RuntimeHandler(this.type, this.handler) : assert(handler != null);
 }
 
 /// A Runtime manages the interface to the Lambda API.
@@ -37,8 +36,8 @@ class _RuntimeHandler {
 /// ```
 ///
 /// Note: You can register an
-class Runtime<T> {
-  Client _client;
+class Runtime {
+  late Client _client;
 
   static final Runtime _singleton = Runtime._internal();
   final Map<String, _RuntimeHandler> _handlers = {};
@@ -54,7 +53,7 @@ class Runtime<T> {
   /// Lists the registered handlers by name.
   /// The name is a simple [String] which reflects
   /// the name of the trigger in the Lambda Execution API.
-  List<String> get handlers => _handlers.keys;
+  List<String> get handlers => _handlers.keys.toList();
 
   /// Checks if a specific handlers has been registered
   /// with the runtime.
@@ -62,27 +61,24 @@ class Runtime<T> {
 
   /// Register a handler function [Handler<T>] with [name]
   /// which digests an event [T].
-  Handler<T> registerHandler<T>(String name, Handler<T> handler) {
-    _handlers[name] = _RuntimeHandler(T, handler);
+  Handler<E> registerHandler<E>(String name, Handler<E> handler) {
+    _handlers[name] = _RuntimeHandler(E, handler);
 
-    return _handlers[name].handler;
+    return handler;
   }
 
-  /// Unregister a handler function [Handler<T>] with [name].
-  Handler<T> deregisterHandler<T>(String name) =>
-      _handlers.remove(name).handler;
+  /// Unregister a handler function [Handler] with [name].
+  Handler? deregisterHandler(String name) =>
+      _handlers.remove(name)?.handler as Handler?;
 
   /// Register an new event to be ingested by a handler.
   /// The type should reflect your type in your handler definition [Handler<T>].
-  void registerEvent<T>(func) {
-    Event.registerEvent<T>(func);
-  }
+  void registerEvent<T>(T Function(Map<String, dynamic>) func) =>
+      Event.registerEvent<T>(func);
 
   /// Deregister an new event to be ingested by a handler.
   /// The type should reflect your type in your handler definition [Handler<T>].
-  void deregisterEvent<T>() {
-    Event.deregisterEvent<T>();
-  }
+  void deregisterEvent<T>() => Event.deregisterEvent<T>();
 
   /// Run the [Runtime] in loop and digest events that are
   /// fetched from the AWS Lambda API Interface. The events are processed
@@ -90,34 +86,31 @@ class Runtime<T> {
   ///
   /// If the invocation of an event was successful the function
   /// sends the [InvocationResult] via [_client.postInvocationResponse(result)] to the API.
-  /// If there is an error during the execution. The execption gets catched
+  /// If there is an error during the execution. The exception gets caught
   /// and the error is posted via [_client.postInvocationError(err)] to the API.
   void invoke() async {
-    do {
-      NextInvocation nextInvocation;
-
-      try {
-        // get the next invocation
-        nextInvocation = await _client.getNextInvocation();
-
-        // creating the new context
-        final context = Context.fromNextInvocation(nextInvocation);
-
-        final func = _handlers[context.handler];
-        if(func == null) {
-          throw RuntimeException('No handler with name "${context.handler}" registered in runtime!');
-        }
-        final event =
-            Event.fromHandler(func.type, await nextInvocation.response);
-        final result = await func.handler(context, event);
-
-        await _client.postInvocationResponse(result);
-      } on Exception catch (error, stacktrace) {
-        await _client.postInvocationError(
-            nextInvocation.requestId, InvocationError(error, stacktrace));
-      }
+    while (true) {
+      await _handleInvocation(await _client.getNextInvocation());
+    }
+  }
+
+  Future<void> _handleInvocation(NextInvocation nextInvocation) async {
+    try {
+      // creating the new context
+      final context = Context.fromNextInvocation(nextInvocation);
 
-      nextInvocation = null;
-    } while (true);
+      final func = _handlers[context.handler];
+      if (func == null) {
+        throw RuntimeException(
+            'No handler with name "${context.handler}" registered in runtime!');
+      }
+      final event = Event.fromHandler(func.type, nextInvocation.response);
+      final result = await func.handler(context, event);
+
+      await _client.postInvocationResponse(context.requestId, result);
+    } catch (error, stacktrace) {
+      await _client.postInvocationError(
+          nextInvocation.requestId, InvocationError(error, stacktrace));
+    }
   }
 }
diff --git a/pubspec.yaml b/pubspec.yaml
index a2ea236f..cf577479 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -6,14 +6,16 @@ homepage: https://github.com/awslabs/aws-lambda-dart-runtime
 documentation: https://awslabs.github.io/aws-lambda-dart-runtime/
 
 environment:
-  sdk: ">=2.6.0 <3.0.0"
+  sdk: '>=2.12.0 <3.0.0'
 
 dependencies:
-  json_annotation: ^3.0.0
+  json_annotation: ^4.0.1
+  meta: ^1.3.0
+  http: ^0.13.1
 
 dev_dependencies:
-  json_serializable: ^3.2.3
+  json_serializable: ^4.1.0
   build_runner: ^1.7.2
-  test: ^1.9.4
-  mockito: ^4.1.1
-  pedantic: ^1.0.0
+  test: ^1.16.8
+  mockito: ^5.0.3
+  pedantic: ^1.11.0
diff --git a/test/alb_event_test.dart b/test/alb_event_test.dart
index 5917753c..9ce66c04 100644
--- a/test/alb_event_test.dart
+++ b/test/alb_event_test.dart
@@ -1,46 +1,46 @@
 import 'dart:io';
 
 import 'package:aws_lambda_dart_runtime/aws_lambda_dart_runtime.dart';
-import "package:test/test.dart";
+import 'package:test/test.dart';
 
 void main() {
-  group("albevent_default", () {
-    test("factory creates response with default values", () {
-      final response = AwsALBResponse.fromString("SUCCESS");
+  group('albevent_default', () {
+    test('factory creates response with default values', () {
+      final response = AwsALBResponse.fromString('SUCCESS');
 
-      expect(response.body, equals("SUCCESS"));
+      expect(response.body, equals('SUCCESS'));
       expect(response.statusCode, equals(200));
       expect(response.isBase64Encoded, equals(false));
     });
 
-    test("factory creates a response with HTTP Status 400", () {
-      final response = AwsALBResponse.fromString("SUCCESS",
+    test('factory creates a response with HTTP Status 400', () {
+      final response = AwsALBResponse.fromString('SUCCESS',
           statusCode: HttpStatus.badRequest);
 
-      expect(response.body, equals("SUCCESS"));
+      expect(response.body, equals('SUCCESS'));
       expect(response.statusCode, equals(HttpStatus.badRequest));
       expect(response.isBase64Encoded, equals(false));
     });
 
-    test("factory creates an event with html/text Header", () {
-      final response = AwsALBResponse.fromString("");
+    test('factory creates an event with html/text Header', () {
+      final response = AwsALBResponse.fromString('');
 
       expect(response.headers,
-          equals({"Content-Type": "text/html; charset=utf-8"}));
+          equals({'Content-Type': 'text/html; charset=utf-8'}));
     });
 
-    test("factory creates an event with JSON Header", () {
-      final response = AwsALBResponse.fromString("",
-          headers: {"Content-Type": "application/json"});
+    test('factory creates an event with JSON Header', () {
+      final response = AwsALBResponse.fromString('',
+          headers: {'Content-Type': 'application/json'});
 
-      expect(response.headers, equals({"Content-Type": "application/json"}));
+      expect(response.headers, equals({'Content-Type': 'application/json'}));
     });
 
-    test("factory creates response which is base64 encoded", () {
+    test('factory creates response which is base64 encoded', () {
       final response =
-          AwsALBResponse.fromString("SUCCESS", isBase64Encoded: true);
+          AwsALBResponse.fromString('SUCCESS', isBase64Encoded: true);
 
-      expect(response.body, equals("SUCCESS"));
+      expect(response.body, equals('SUCCESS'));
       expect(response.statusCode, equals(HttpStatus.ok));
       expect(response.isBase64Encoded, equals(true));
     });
diff --git a/test/apigateway_event_test.dart b/test/apigateway_event_test.dart
index 09d7dc02..71be7e13 100644
--- a/test/apigateway_event_test.dart
+++ b/test/apigateway_event_test.dart
@@ -3,32 +3,33 @@ import 'dart:io' show File;
 import 'dart:convert';
 
 import 'package:aws_lambda_dart_runtime/aws_lambda_dart_runtime.dart';
-import "package:test/test.dart";
+import 'package:test/test.dart';
 
 final file = 'data/apigateway_event.json';
 
-final String contents = new File(file).readAsStringSync();
-final Map<String, dynamic> json = jsonDecode(contents);
+final String contents = File(file).readAsStringSync();
+final Map<String, dynamic>? json =
+    jsonDecode(contents) as Map<String, dynamic>?;
 
 void main() {
-  group("apigateway_default", () {
-    test("json got parsed and creates an event", () async {
-      final event = AwsApiGatewayEvent.fromJson(json);
+  group('apigateway_default', () {
+    test('json got parsed and creates an event', () async {
+      final event = AwsApiGatewayEvent.fromJson(json!);
 
-      expect(event.body, equals(jsonEncode({"foo": "bar"})));
-      expect(event.path, equals("/test/hello"));
-      expect(event.headers.acceptEncoding,
-          equals("gzip, deflate, lzma, sdch, br"));
-      expect(event.requestContext.httpMethod, equals("POST"));
-      expect(event.requestContext.accountId, equals("123456789012"));
-      expect(event.requestContext.requestId,
-          equals("41b45ea3-70b5-11e6-b7bd-69b5aaebc7d9"));
-      expect(event.queryStringParameters, equals({"name": "me"}));
-      expect(event.requestContext.resourcePath, equals("/{proxy+}"));
-      expect(event.headers.raw['Accept-Encoding'],
-          equals("gzip, deflate, lzma, sdch, br"));
+      expect(event.body, equals(jsonEncode({'foo': 'bar'})));
+      expect(event.path, equals('/test/hello'));
+      expect(event.headers!.acceptEncoding,
+          equals('gzip, deflate, lzma, sdch, br'));
+      expect(event.requestContext!.httpMethod, equals('POST'));
+      expect(event.requestContext!.accountId, equals('123456789012'));
+      expect(event.requestContext!.requestId,
+          equals('41b45ea3-70b5-11e6-b7bd-69b5aaebc7d9'));
+      expect(event.queryStringParameters, equals({'name': 'me'}));
+      expect(event.requestContext!.resourcePath, equals('/{proxy+}'));
+      expect(event.headers!.raw['Accept-Encoding'],
+          equals('gzip, deflate, lzma, sdch, br'));
     });
-    test("factory creates event with default values", () {
+    test('factory creates event with default values', () {
       final response = AwsApiGatewayResponse.fromJson({});
 
       expect(response.body, equals({}.toString()));
@@ -36,7 +37,7 @@ void main() {
       expect(response.isBase64Encoded, equals(false));
     });
 
-    test("factory creates an event with HTTP Status 400", () {
+    test('factory creates an event with HTTP Status 400', () {
       final response =
           AwsApiGatewayResponse.fromJson({}, statusCode: HttpStatus.badRequest);
 
@@ -45,21 +46,21 @@ void main() {
       expect(response.isBase64Encoded, equals(false));
     });
 
-    test("factory creates an event with JSON Header", () {
+    test('factory creates an event with JSON Header', () {
       final response = AwsApiGatewayResponse.fromJson({});
 
-      expect(response.headers, equals({"Content-Type": "application/json"}));
+      expect(response.headers, equals({'Content-Type': 'application/json'}));
     });
 
-    test("factory creates an event with text/html Header", () {
+    test('factory creates an event with text/html Header', () {
       final response = AwsApiGatewayResponse.fromJson({},
-          headers: {"Content-Type": "text/html; charset=utf-8"});
+          headers: {'Content-Type': 'text/html; charset=utf-8'});
 
       expect(response.headers,
-          equals({"Content-Type": "text/html; charset=utf-8"}));
+          equals({'Content-Type': 'text/html; charset=utf-8'}));
     });
 
-    test("factory creates an event with is based 64 encoded", () {
+    test('factory creates an event with is based 64 encoded', () {
       final response =
           AwsApiGatewayResponse.fromJson({}, isBase64Encoded: true);
 
diff --git a/test/client_test.dart b/test/client_test.dart
index 6552fe6f..1a3d2f5e 100644
--- a/test/client_test.dart
+++ b/test/client_test.dart
@@ -1,20 +1,20 @@
-import "package:test/test.dart";
+import 'package:test/test.dart';
 
 import 'package:aws_lambda_dart_runtime/client/client.dart';
 
 void main() {
   group('invocation', () {
-    test("invocation result gets populated", () {
-      final result = InvocationResult("1234567890", "SUCCESS");
+    test('invocation result gets populated', () {
+      final result = InvocationResult('1234567890', 'SUCCESS');
 
-      expect(result.requestId, "1234567890");
-      expect(result.body, "SUCCESS");
+      expect(result.requestId, '1234567890');
+      expect(result.body, 'SUCCESS');
     });
 
-    test("invocation error gets populated", () {
-      final stateError = new StateError("foo");
+    test('invocation error gets populated', () {
+      final stateError = StateError('foo');
       final invocationError =
-          InvocationError(stateError, new StackTrace.fromString(""));
+          InvocationError(stateError, StackTrace.fromString(''));
 
       expect(invocationError.error, stateError);
     });
diff --git a/test/cloudwatch_event_test.dart b/test/cloudwatch_event_test.dart
index 42717a24..2bbbcd12 100644
--- a/test/cloudwatch_event_test.dart
+++ b/test/cloudwatch_event_test.dart
@@ -2,24 +2,24 @@ import 'dart:convert';
 import 'dart:io' show File;
 
 import 'package:aws_lambda_dart_runtime/aws_lambda_dart_runtime.dart';
-import "package:test/test.dart";
+import 'package:test/test.dart';
 
 final file = 'data/cloudwatch_event.json';
 
-final String contents = new File(file).readAsStringSync();
-final Map<String, dynamic> json = jsonDecode(contents);
+final String contents = File(file).readAsStringSync();
+final json = jsonDecode(contents) as Map<String, dynamic>?;
 
 void main() {
-  group("cloudwatch_default", () {
-    test("json got parsed and creates an event", () async {
-      final event = AwsCloudwatchEvent.fromJson(json);
+  group('cloudwatch_default', () {
+    test('json got parsed and creates an event', () async {
+      final event = AwsCloudwatchEvent.fromJson(json!);
 
-      expect(event.account, equals("1234567890"));
-      expect(event.region, equals("eu-west-1"));
-      expect(event.detailType, equals("Scheduled Event"));
-      expect(event.id, equals("cdc73f9d-aea9-11e3-9d5a-835b769c0d9c"));
+      expect(event.account, equals('1234567890'));
+      expect(event.region, equals('eu-west-1'));
+      expect(event.detailType, equals('Scheduled Event'));
+      expect(event.id, equals('cdc73f9d-aea9-11e3-9d5a-835b769c0d9c'));
       expect(event.detail, equals({}));
-      expect(event.time, equals(DateTime.parse("1970-01-01T00:00:00Z")));
+      expect(event.time, equals(DateTime.parse('1970-01-01T00:00:00Z')));
     });
   });
 }
diff --git a/test/cloudwatch_log_event_test.dart b/test/cloudwatch_log_event_test.dart
index 316e4c5f..cb6faebb 100644
--- a/test/cloudwatch_log_event_test.dart
+++ b/test/cloudwatch_log_event_test.dart
@@ -2,23 +2,23 @@ import 'dart:convert';
 import 'dart:io' show File;
 
 import 'package:aws_lambda_dart_runtime/aws_lambda_dart_runtime.dart';
-import "package:test/test.dart";
+import 'package:test/test.dart';
 
 final file = 'data/cloudwatch_log_event.json';
 
-final String contents = new File(file).readAsStringSync();
-final Map<String, dynamic> json = jsonDecode(contents);
+final String contents = File(file).readAsStringSync();
+final json = jsonDecode(contents) as Map<String, dynamic>?;
 
 void main() {
-  group("cloudwatch_log_default", () {
-    test("json got parsed and creates an event", () async {
-      final event = AwsCloudwatchLogEvent.fromJson(json);
+  group('cloudwatch_log_default', () {
+    test('json got parsed and creates an event', () async {
+      final event = AwsCloudwatchLogEvent.fromJson(json!);
 
       expect(
           event.awslogs,
           equals({
-            "data":
-                "H4sIAAAAAAAAAHWPwQqCQBCGX0Xm7EFtK+smZBEUgXoLCdMhFtKV3akI8d0bLYmibvPPN3wz00CJxmQnTO41whwWQRIctmEcB6sQbFC3CjW3XW8kxpOpP+OC22d1Wml1qZkQGtoMsScxaczKN3plG8zlaHIta5KqWsozoTYw3/djzwhpLwivWFGHGpAFe7DL68JlBUk+l7KSN7tCOEJ4M3/qOI49vMHj+zCKdlFqLaU2ZHV2a4Ct/an0/ivdX8oYc1UVX860fQDQiMdxRQEAAA=="
+            'data':
+                'H4sIAAAAAAAAAHWPwQqCQBCGX0Xm7EFtK+smZBEUgXoLCdMhFtKV3akI8d0bLYmibvPPN3wz00CJxmQnTO41whwWQRIctmEcB6sQbFC3CjW3XW8kxpOpP+OC22d1Wml1qZkQGtoMsScxaczKN3plG8zlaHIta5KqWsozoTYw3/djzwhpLwivWFGHGpAFe7DL68JlBUk+l7KSN7tCOEJ4M3/qOI49vMHj+zCKdlFqLaU2ZHV2a4Ct/an0/ivdX8oYc1UVX860fQDQiMdxRQEAAA=='
           }));
     });
   });
diff --git a/test/cognito_event_test.dart b/test/cognito_event_test.dart
index 24ba6966..25f69ed5 100644
--- a/test/cognito_event_test.dart
+++ b/test/cognito_event_test.dart
@@ -2,24 +2,24 @@ import 'dart:convert';
 import 'dart:io' show File;
 
 import 'package:aws_lambda_dart_runtime/aws_lambda_dart_runtime.dart';
-import "package:test/test.dart";
+import 'package:test/test.dart';
 
 final file = 'data/cognito_event.json';
 
-final String contents = new File(file).readAsStringSync();
-final Map<String, dynamic> json = jsonDecode(contents);
+final String contents = File(file).readAsStringSync();
+final json = jsonDecode(contents) as Map<String, dynamic>?;
 
 void main() {
-  group("cognito_default", () {
-    test("json got parsed and creates an event", () async {
-      final event = AwsCognitoEvent.fromJson(json);
+  group('cognito_default', () {
+    test('json got parsed and creates an event', () async {
+      final event = AwsCognitoEvent.fromJson(json!);
 
       expect(event.version, equals(1));
-      expect(event.userPoolId, equals("1234567"));
-      expect(event.userName, equals("foo"));
-      expect(event.response.smsMessage, equals("foo"));
-      expect(event.response.emailSubject, equals("foo"));
-      expect(event.response.emailMessage, equals("bar"));
+      expect(event.userPoolId, equals('1234567'));
+      expect(event.userName, equals('foo'));
+      expect(event.response!.smsMessage, equals('foo'));
+      expect(event.response!.emailSubject, equals('foo'));
+      expect(event.response!.emailMessage, equals('bar'));
     });
   });
 }
diff --git a/test/common.dart b/test/common.dart
deleted file mode 100644
index 291d16c5..00000000
--- a/test/common.dart
+++ /dev/null
@@ -1,49 +0,0 @@
-import 'dart:io';
-
-import 'package:mockito/mockito.dart';
-
-class MockHttpClientResponse extends Mock implements HttpClientResponse {
-  MockHttpClientResponse(this.statusCode,
-      {this.result, this.headers, this.body});
-
-  @override
-  final int statusCode;
-
-  final String result;
-
-  @override
-  final HttpHeaders headers;
-
-  // encode the response body as bytes.
-  final List<int> body;
-}
-
-/// A mocked [HttpHeaders] that ignores all writes.
-class MockHttpHeaders extends HttpHeaders {
-  @override
-  List<String> operator [](String name) => <String>[];
-
-  @override
-  void add(String name, Object value, {bool preserveHeaderCase = false}) {}
-
-  @override
-  void clear() {}
-
-  @override
-  void forEach(void Function(String name, List<String> values) f) {}
-
-  @override
-  void noFolding(String name) {}
-
-  @override
-  void remove(String name, Object value) {}
-
-  @override
-  void removeAll(String name) {}
-
-  @override
-  void set(String name, Object value, {bool preserveHeaderCase = false}) {}
-
-  @override
-  String value(String name) => null;
-}
diff --git a/test/context_test.dart b/test/context_test.dart
index d6bfaad8..d587bd76 100644
--- a/test/context_test.dart
+++ b/test/context_test.dart
@@ -1,48 +1,43 @@
-import "dart:convert";
-
-import "package:test/test.dart";
+import 'package:http/http.dart';
+import 'package:test/test.dart';
 
 import 'package:aws_lambda_dart_runtime/runtime/context.dart';
 import 'package:aws_lambda_dart_runtime/client/client.dart';
-import 'common.dart';
 
 void main() {
   group('context', () {
-    test("Context gets initialized with a Platform.environment", () async {
-      final Map<String, String> environment = {
-        "_HANDLER": "foo",
-        "AWS_LAMBDA_FUNCTION_NAME": "bar",
-        "AWS_LAMBDA_FUNCTION_VERSION": "1",
-        "AWS_LAMBDA_LOG_GROUP_NAME": "foo",
-        "AWS_LAMBDA_LOG_STREAM_NAME": "foo",
-        "AWS_LAMBDA_FUNCTION_MEMORY_SIZE": "128",
-        "AWS_REGION": "eu-west-1",
-        "AWS_EXECUTION_ENV": "foo",
-        "AWS_ACCESS_KEY_ID": "secret",
-        "AWS_SECRET_ACCESS_KEY": "key",
-        "AWS_SESSION_TOKEN": "1234567890"
+    test('Context gets initialized with a Platform.environment', () async {
+      final environment = {
+        '_HANDLER': 'foo',
+        'AWS_LAMBDA_FUNCTION_NAME': 'bar',
+        'AWS_LAMBDA_FUNCTION_VERSION': '1',
+        'AWS_LAMBDA_LOG_GROUP_NAME': 'foo',
+        'AWS_LAMBDA_LOG_STREAM_NAME': 'foo',
+        'AWS_LAMBDA_FUNCTION_MEMORY_SIZE': '128',
+        'AWS_REGION': 'eu-west-1',
+        'AWS_EXECUTION_ENV': 'foo',
+        'AWS_ACCESS_KEY_ID': 'secret',
+        'AWS_SECRET_ACCESS_KEY': 'key',
+        'AWS_SESSION_TOKEN': '1234567890'
       };
 
-      final headers = MockHttpHeaders();
-
-      final response = MockHttpClientResponse(200,
-          result: "", headers: headers, body: utf8.encode("{}"));
-      final nextInvocation = await NextInvocation.fromResponse(response);
+      final nextInvocation =
+          await NextInvocation.fromResponse(Response('{}', 200));
 
       final ctx = Context.fromNextInvocation(nextInvocation);
 
-      expect(ctx.handler, environment["_HANDLER"]);
-      expect(ctx.functionName, environment["AWS_LAMBDA_FUNCTION_NAME"]);
-      expect(ctx.functionVersion, environment["AWS_LAMBDA_FUNCTION_VERSION"]);
-      expect(ctx.logGroupName, environment["AWS_LAMBDA_LOG_GROUP_NAME"]);
-      expect(ctx.logStreamName, environment["AWS_LAMBDA_LOG_STREAM_NAME"]);
+      expect(ctx.handler, environment['_HANDLER']);
+      expect(ctx.functionName, environment['AWS_LAMBDA_FUNCTION_NAME']);
+      expect(ctx.functionVersion, environment['AWS_LAMBDA_FUNCTION_VERSION']);
+      expect(ctx.logGroupName, environment['AWS_LAMBDA_LOG_GROUP_NAME']);
+      expect(ctx.logStreamName, environment['AWS_LAMBDA_LOG_STREAM_NAME']);
       expect(ctx.functionMemorySize,
-          environment["AWS_LAMBDA_FUNCTION_MEMORY_SIZE"]);
-      expect(ctx.region, environment["AWS_REGION"]);
-      expect(ctx.executionEnv, environment["AWS_EXECUTION_ENV"]);
-      expect(ctx.accessKey, environment["AWS_ACCESS_KEY_ID"]);
-      expect(ctx.secretAccessKey, environment["AWS_SECRET_ACCESS_KEY"]);
-      expect(ctx.sessionToken, environment["AWS_SESSION_TOKEN"]);
+          environment['AWS_LAMBDA_FUNCTION_MEMORY_SIZE']);
+      expect(ctx.region, environment['AWS_REGION']);
+      expect(ctx.executionEnv, environment['AWS_EXECUTION_ENV']);
+      expect(ctx.accessKey, environment['AWS_ACCESS_KEY_ID']);
+      expect(ctx.secretAccessKey, environment['AWS_SECRET_ACCESS_KEY']);
+      expect(ctx.sessionToken, environment['AWS_SESSION_TOKEN']);
     });
-  }, skip: "the tests are not quite ready");
+  }, skip: 'the tests are not quite ready');
 }
diff --git a/test/dynamodb_event_test.dart b/test/dynamodb_event_test.dart
index 31ebb878..01daec3c 100644
--- a/test/dynamodb_event_test.dart
+++ b/test/dynamodb_event_test.dart
@@ -2,19 +2,19 @@ import 'dart:convert';
 import 'dart:io' show File;
 
 import 'package:aws_lambda_dart_runtime/aws_lambda_dart_runtime.dart';
-import "package:test/test.dart";
+import 'package:test/test.dart';
 
 final file = 'data/dynamodb_event.json';
 
-final String contents = new File(file).readAsStringSync();
-final Map<String, dynamic> json = jsonDecode(contents);
+final String contents = File(file).readAsStringSync();
+final json = jsonDecode(contents) as Map<String, dynamic>?;
 
 void main() {
-  group("dynamodb_default", () {
-    test("json got parsed and creates an event", () async {
-      final event = AwsDynamoDBUpdateEvent.fromJson(json);
+  group('dynamodb_default', () {
+    test('json got parsed and creates an event', () async {
+      final event = AwsDynamoDBUpdateEvent.fromJson(json!);
 
-      expect(event.records.length, equals(1));
+      expect(event.records!.length, equals(1));
     });
   });
 }
diff --git a/test/event_test.dart b/test/event_test.dart
index f7f7c416..4a04d655 100644
--- a/test/event_test.dart
+++ b/test/event_test.dart
@@ -1,8 +1,8 @@
-import "package:test/test.dart";
+import 'package:test/test.dart';
 
 import 'package:aws_lambda_dart_runtime/runtime/event.dart';
 
-class CustomTestEvent {
+class CustomTestEvent extends Event {
   factory CustomTestEvent.fromJson(Map<String, dynamic> json) {
     return CustomTestEvent();
   }
@@ -12,16 +12,16 @@ class CustomTestEvent {
 
 void main() {
   group('runtime', () {
-    test("Custom event is add to the events", () {
+    test('Custom event is add to the events', () {
       Event.registerEvent<CustomTestEvent>(
-          (Map<String, dynamic> json) => CustomTestEvent.fromJson({}));
+          (Map<String, dynamic>? json) => CustomTestEvent.fromJson({}));
 
       expect(Event.exists<CustomTestEvent>(), true);
     });
 
-    test("Custom event is deregistered", () {
+    test('Custom event is deregistered', () {
       Event.registerEvent<CustomTestEvent>(
-          (Map<String, dynamic> json) => CustomTestEvent.fromJson({}));
+          (Map<String, dynamic>? json) => CustomTestEvent.fromJson({}));
 
       Event.deregisterEvent<CustomTestEvent>();
 
diff --git a/test/exception_test.dart b/test/exception_test.dart
index 9d620fbd..e98457c0 100644
--- a/test/exception_test.dart
+++ b/test/exception_test.dart
@@ -1,17 +1,17 @@
-import "package:test/test.dart";
+import 'package:test/test.dart';
 
 import 'package:aws_lambda_dart_runtime/aws_lambda_dart_runtime.dart';
 
 void main() {
-  group("runtime exception", () {
-    test("return the cause a string", () {
-      final exception = RuntimeException("missing handler");
-      expect(exception.toString(), equals("RuntimeException: missing handler"));
+  group('runtime exception', () {
+    test('return the cause a string', () {
+      final exception = RuntimeException('missing handler');
+      expect(exception.toString(), equals('RuntimeException: missing handler'));
     });
 
-    test("catch exception with cause", () {
+    test('catch exception with cause', () {
       try {
-        throw RuntimeException("missing handler");
+        throw RuntimeException('missing handler');
       } on RuntimeException catch (e) {
         expect(e.cause, 'missing handler');
         return;
diff --git a/test/kinesis_data_firehose_event.dart b/test/kinesis_data_firehose_event.dart
index 34a7f702..716d0fec 100644
--- a/test/kinesis_data_firehose_event.dart
+++ b/test/kinesis_data_firehose_event.dart
@@ -2,28 +2,28 @@ import 'dart:convert';
 import 'dart:io' show File;
 
 import 'package:aws_lambda_dart_runtime/aws_lambda_dart_runtime.dart';
-import "package:test/test.dart";
+import 'package:test/test.dart';
 
 final file = 'data/kinesis_data_firehose_event.json';
 
-final String contents = new File(file).readAsStringSync();
-final Map<String, dynamic> json = jsonDecode(contents);
+final String contents = File(file).readAsStringSync();
+final json = jsonDecode(contents) as Map<String, dynamic>?;
 
 void main() {
-  group("kinesis_firehose_default", () {
-    test("json got parsed and creates an event", () async {
-      final event = AwsKinesisFirehoseDataEvent.fromJson(json);
+  group('kinesis_firehose_default', () {
+    test('json got parsed and creates an event', () async {
+      final event = AwsKinesisFirehoseDataEvent.fromJson(json!);
 
-      expect(event.records.length, equals(1));
-      expect(event.invocationId, equals("invocationIdExample"));
-      expect(event.deliveryStreamArn, equals("arn:aws:kinesis:EXAMPLE"));
-      expect(event.region, equals("eu-west-1"));
-      expect(event.records[0].recordId,
-          equals("49546986683135544286507457936321625675700192471156785154"));
+      expect(event.records!.length, equals(1));
+      expect(event.invocationId, equals('invocationIdExample'));
+      expect(event.deliveryStreamArn, equals('arn:aws:kinesis:EXAMPLE'));
+      expect(event.region, equals('eu-west-1'));
+      expect(event.records![0].recordId,
+          equals('49546986683135544286507457936321625675700192471156785154'));
       expect(
-          event.records[0].approximateArrivalTimestamp, equals(1495072949453));
-      expect(event.records[0].data,
-          equals("SGVsbG8sIHRoaXMgaXMgYSB0ZXN0IDEyMy4="));
+          event.records![0].approximateArrivalTimestamp, equals(1495072949453));
+      expect(event.records![0].data,
+          equals('SGVsbG8sIHRoaXMgaXMgYSB0ZXN0IDEyMy4='));
     });
   });
 }
diff --git a/test/kinesis_data_stream_event_test.dart b/test/kinesis_data_stream_event_test.dart
index dc082785..0ad8bd66 100644
--- a/test/kinesis_data_stream_event_test.dart
+++ b/test/kinesis_data_stream_event_test.dart
@@ -2,35 +2,36 @@ import 'dart:convert';
 import 'dart:io' show File;
 
 import 'package:aws_lambda_dart_runtime/aws_lambda_dart_runtime.dart';
-import "package:test/test.dart";
+import 'package:test/test.dart';
 
 final file = 'data/kinesis_data_stream_event.json';
 
-final String contents = new File(file).readAsStringSync();
-final Map<String, dynamic> json = jsonDecode(contents);
+final String contents = File(file).readAsStringSync();
+final json = jsonDecode(contents) as Map<String, dynamic>?;
 
 void main() {
-  group("kinesis_default", () {
-    test("json got parsed and creates an event", () async {
-      final event = AwsKinesisDataStreamEvent.fromJson(json);
+  group('kinesis_default', () {
+    test('json got parsed and creates an event', () async {
+      final event = AwsKinesisDataStreamEvent.fromJson(json!);
 
-      expect(event.records.length, equals(1));
-      expect(event.records[0].eventSource, equals("aws:kinesis"));
+      expect(event.records!.length, equals(1));
+      expect(event.records![0].eventSource, equals('aws:kinesis'));
       expect(
-          event.records[0].eventID,
+          event.records![0].eventID,
           equals(
-              "shardId-000000000000:49545115243490985018280067714973144582180062593244200961"));
+              'shardId-000000000000:49545115243490985018280067714973144582180062593244200961'));
       expect(
-          event.records[0].eventSourceARN, equals("arn:aws:kinesis:EXAMPLE"));
-      expect(event.records[0].awsRegion, equals("eu-west-1"));
-      expect(event.records[0].eventVersion, equals("1.0"));
+          event.records![0].eventSourceARN, equals('arn:aws:kinesis:EXAMPLE'));
+      expect(event.records![0].awsRegion, equals('eu-west-1'));
+      expect(event.records![0].eventVersion, equals('1.0'));
       expect(
-          event.records[0].invokeIdentityArn, equals("arn:aws:iam::EXAMPLE"));
-      expect(event.records[0].kinesis.partitionKey, equals("partitionKey-03"));
-      expect(event.records[0].kinesis.data,
-          equals("SGVsbG8sIHRoaXMgaXMgYSB0ZXN0IDEyMy4="));
-      expect(event.records[0].kinesis.sequenceNumber,
-          equals("49545115243490985018280067714973144582180062593244200961"));
+          event.records![0].invokeIdentityArn, equals('arn:aws:iam::EXAMPLE'));
+      expect(
+          event.records![0].kinesis!.partitionKey, equals('partitionKey-03'));
+      expect(event.records![0].kinesis!.data,
+          equals('SGVsbG8sIHRoaXMgaXMgYSB0ZXN0IDEyMy4='));
+      expect(event.records![0].kinesis!.sequenceNumber,
+          equals('49545115243490985018280067714973144582180062593244200961'));
     });
   });
 }
diff --git a/test/runtime_test.dart b/test/runtime_test.dart
index ecc614ae..e8edd5a6 100644
--- a/test/runtime_test.dart
+++ b/test/runtime_test.dart
@@ -1,44 +1,43 @@
-import "package:test/test.dart";
+import 'package:test/test.dart';
 
 import 'package:aws_lambda_dart_runtime/aws_lambda_dart_runtime.dart';
 
 void main() {
   group('runtime', () {
-    test("instance is created without error", () {
+    test('instance is created without error', () {
       expect(() => Runtime(), returnsNormally);
     });
 
-    test("instance is same accross invocation", () async {
-      final runtime = await Runtime();
+    test('instance is same across invocation', () async {
+      final runtime = Runtime();
 
-      expect(runtime, await Runtime());
+      expect(runtime, Runtime());
     });
 
-    test("successfully add a handler to runtime", () async {
-      final runtime = await Runtime();
+    test('successfully add a handler to runtime', () async {
+      final runtime = Runtime();
 
-      final Handler<AwsS3Event> testHandler = (context, event) async {
-        return new InvocationResult(context.requestId, "HELLO WORLD");
+      final Handler testHandler = (context, event) async {
+        return true;
       };
 
-      final addHandler = runtime.registerHandler("test.handler", testHandler);
+      final addHandler = runtime.registerHandler('test.handler', testHandler);
 
-      expect(runtime.handlerExists("test.handler"), equals(true));
+      expect(runtime.handlerExists('test.handler'), equals(true));
       expect(addHandler, equals(testHandler));
     });
 
-    test("successfully deregister a handler to runtime", () async {
-      final runtime = await Runtime();
+    test('successfully deregister a handler to runtime', () async {
+      final runtime = Runtime();
 
-      final Handler<AwsS3Event> testHandler = (context, event) async {
-        return new InvocationResult(context.requestId, "HELLO WORLD");
+      final testHandler = (context, event) async {
+        return true;
       };
 
-      runtime.registerHandler("test.handler", testHandler);
-      final removedHandler =
-          runtime.deregisterHandler<AwsS3Event>("test.handler");
+      runtime.registerHandler('test.handler', testHandler);
+      final removedHandler = runtime.deregisterHandler('test.handler');
 
-      expect(runtime.handlerExists("test.handler"), equals(false));
+      expect(runtime.handlerExists('test.handler'), equals(false));
       expect(removedHandler, equals(testHandler));
     });
   });
diff --git a/test/s3_event.dart b/test/s3_event.dart
index 3f5a3d41..b02c59d4 100644
--- a/test/s3_event.dart
+++ b/test/s3_event.dart
@@ -2,29 +2,29 @@ import 'dart:convert';
 import 'dart:io' show File;
 
 import 'package:aws_lambda_dart_runtime/aws_lambda_dart_runtime.dart';
-import "package:test/test.dart";
+import 'package:test/test.dart';
 
 final file = 'data/s3_event.json';
 
-final String contents = new File(file).readAsStringSync();
-final Map<String, dynamic> json = jsonDecode(contents);
+final String contents = File(file).readAsStringSync();
+final json = jsonDecode(contents) as Map<String, dynamic>?;
 
 void main() {
-  group("s3_default", () {
-    test("json got parsed and creates an event", () async {
-      final event = AwsS3Event.fromJson(json);
+  group('s3_default', () {
+    test('json got parsed and creates an event', () async {
+      final event = AwsS3Event.fromJson(json!);
 
-      expect(event.records[0].eventVersion, equals("2.0"));
-      expect(event.records[0].eventSource, equals("aws:s3"));
-      expect(event.records[0].awsRegion, equals("eu-west-1"));
-      expect(event.records[0].eventTime,
-          equals(DateTime.parse("1970-01-01T00:00:00.000Z")));
-      expect(event.records[0].eventName, equals("ObjectCreated:Put"));
-      expect(event.records[0].userIdentity.principalId, equals("EXAMPLE"));
-      expect(event.records[0].requestParameters["sourceIPAddress"],
-          equals("127.0.0.1"));
-      expect(event.records[0].s3.s3SchemaVersion, equals("1.0"));
-      expect(event.records[0].s3.configurationId, equals("testConfigRule"));
+      expect(event.records![0].eventVersion, equals('2.0'));
+      expect(event.records![0].eventSource, equals('aws:s3'));
+      expect(event.records![0].awsRegion, equals('eu-west-1'));
+      expect(event.records![0].eventTime,
+          equals(DateTime.parse('1970-01-01T00:00:00.000Z')));
+      expect(event.records![0].eventName, equals('ObjectCreated:Put'));
+      expect(event.records![0].userIdentity!.principalId, equals('EXAMPLE'));
+      expect(event.records![0].requestParameters!['sourceIPAddress'],
+          equals('127.0.0.1'));
+      expect(event.records![0].s3!.s3SchemaVersion, equals('1.0'));
+      expect(event.records![0].s3!.configurationId, equals('testConfigRule'));
     });
   });
 }
diff --git a/test/sqs_event_test.dart b/test/sqs_event_test.dart
index 64f5f088..7782b96a 100644
--- a/test/sqs_event_test.dart
+++ b/test/sqs_event_test.dart
@@ -2,29 +2,29 @@ import 'dart:convert';
 import 'dart:io' show File;
 
 import 'package:aws_lambda_dart_runtime/aws_lambda_dart_runtime.dart';
-import "package:test/test.dart";
+import 'package:test/test.dart';
 
 final file = 'data/sqs_event.json';
 
-final String contents = new File(file).readAsStringSync();
-final Map<String, dynamic> json = jsonDecode(contents);
+final String contents = File(file).readAsStringSync();
+final json = jsonDecode(contents) as Map<String, dynamic>?;
 
 void main() {
-  group("sqs_default", () {
-    test("json got parsed and creates an event", () async {
-      final event = AwsSQSEvent.fromJson(json);
+  group('sqs_default', () {
+    test('json got parsed and creates an event', () async {
+      final event = AwsSQSEvent.fromJson(json!);
 
-      expect(event.records.length, equals(1));
-      expect(event.records[0].md5OfBody,
-          equals("7b270e59b47ff90a553787216d55d91d"));
-      expect(event.records[0].eventSource, equals("aws:sqs"));
-      expect(event.records[0].eventSourceARN,
-          equals("arn:aws:sqs:eu-west-1:123456789012:MyQueue"));
-      expect(event.records[0].awsRegion, equals("eu-west-1"));
-      expect(event.records[0].body, equals("Hello from SQS!"));
-      expect(event.records[0].messageId,
-          equals("19dd0b57-b21e-4ac1-bd88-01bbb068cb78"));
-      expect(event.records[0].receiptHandle, equals("MessageReceiptHandle"));
+      expect(event.records!.length, equals(1));
+      expect(event.records![0].md5OfBody,
+          equals('7b270e59b47ff90a553787216d55d91d'));
+      expect(event.records![0].eventSource, equals('aws:sqs'));
+      expect(event.records![0].eventSourceARN,
+          equals('arn:aws:sqs:eu-west-1:123456789012:MyQueue'));
+      expect(event.records![0].awsRegion, equals('eu-west-1'));
+      expect(event.records![0].body, equals('Hello from SQS!'));
+      expect(event.records![0].messageId,
+          equals('19dd0b57-b21e-4ac1-bd88-01bbb068cb78'));
+      expect(event.records![0].receiptHandle, equals('MessageReceiptHandle'));
     });
   });
 }
diff --git a/test/testing.dart b/test/testing.dart
deleted file mode 100644
index 0b27728f..00000000
--- a/test/testing.dart
+++ /dev/null
@@ -1,3 +0,0 @@
-library testing;
-
-export 'common.dart';