diff --git a/.github/workflows/test_build_multi_platform.yml b/.github/workflows/test_build_multi_platform.yml
index 0f5d2f764..801601832 100644
--- a/.github/workflows/test_build_multi_platform.yml
+++ b/.github/workflows/test_build_multi_platform.yml
@@ -16,7 +16,7 @@ jobs:
   Build-ad-windows:
     strategy:
       matrix:
-        java: [ 11, 17 ]
+        java: [ 11, 17, 21 ]
     name: Build and Test Anomaly Detection Plugin on Windows
     runs-on: windows-latest
     env:
@@ -49,7 +49,7 @@ jobs:
     needs: Get-CI-Image-Tag
     strategy:
       matrix:
-        java: [11,17]
+        java: [11, 17, 21]
       fail-fast: false
     name: Build and Test Anomaly detection Plugin
     runs-on: ubuntu-latest
@@ -89,7 +89,7 @@ jobs:
   Build-ad-macos:
     strategy:
       matrix:
-        java: [11,17,20]
+        java: [11,17,21]
       fail-fast: false
 
     name: Build and Test Anomaly detection Plugin
diff --git a/.github/workflows/test_bwc.yml b/.github/workflows/test_bwc.yml
index bc166633b..953f62009 100644
--- a/.github/workflows/test_bwc.yml
+++ b/.github/workflows/test_bwc.yml
@@ -17,7 +17,7 @@ jobs:
     needs: Get-CI-Image-Tag
     strategy:
       matrix:
-        java: [11,17]
+        java: [11,17,21]
       fail-fast: false
 
     name: Test Anomaly detection BWC
diff --git a/.github/workflows/test_security.yml b/.github/workflows/test_security.yml
index 5c1df108a..352d2568f 100644
--- a/.github/workflows/test_security.yml
+++ b/.github/workflows/test_security.yml
@@ -11,7 +11,7 @@ jobs:
   Build-ad:
     strategy:
       matrix:
-        java: [11,17]
+        java: [11,17,21]
       fail-fast: false
 
     name: Security test workflow for Anomaly Detection
diff --git a/build.gradle b/build.gradle
index 951d4af60..89996ce33 100644
--- a/build.gradle
+++ b/build.gradle
@@ -61,11 +61,10 @@ buildscript {
 }
 
 plugins {
-    id 'nebula.ospackage' version "8.3.0" apply false
-    id "com.diffplug.gradle.spotless" version "3.26.1"
+    id 'com.netflix.nebula.ospackage' version "11.5.0"
+    id "com.diffplug.spotless" version "6.24.0"
     id 'java-library'
-    // Gradle 7.6 support was added in test-retry 1.4.0.
-    id 'org.gradle.test-retry' version '1.4.1'
+    id 'org.gradle.test-retry' version '1.5.7'
 }
 
 tasks.withType(JavaCompile) {
@@ -122,6 +121,9 @@ allprojects {
     plugins.withId('java') {
         sourceCompatibility = targetCompatibility = JavaVersion.VERSION_11
     }
+    plugins.withId('jacoco') {
+        jacoco.toolVersion = '0.8.11'
+    }
 }
 
 ext {
@@ -146,10 +148,10 @@ configurations.all {
         force "org.apache.httpcomponents:httpcore:${versions.httpcore}"
         force "commons-codec:commons-codec:${versions.commonscodec}"
 
-        force "org.mockito:mockito-core:2.25.0"
-        force "org.objenesis:objenesis:3.0.1"
-        force "net.bytebuddy:byte-buddy:1.9.15"
-        force "net.bytebuddy:byte-buddy-agent:1.9.15"
+        force "org.mockito:mockito-core:5.9.0"
+        force "org.objenesis:objenesis:3.3"
+        force "net.bytebuddy:byte-buddy:1.14.9"
+        force "net.bytebuddy:byte-buddy-agent:1.14.9"
         force "com.google.code.gson:gson:2.8.9"
         force "junit:junit:4.13.2"
     }
@@ -727,8 +729,8 @@ jacocoTestCoverageVerification {
 
 jacocoTestReport {
     reports {
-        xml.enabled = true
-        html.enabled = true
+        xml.required = true
+        html.required = true
     }
 }
 
@@ -773,31 +775,21 @@ dependencies {
     }
 
     testImplementation group: 'pl.pragmatists', name: 'JUnitParams', version: '1.1.1'
-    testImplementation group: 'org.mockito', name: 'mockito-core', version: '2.25.0'
-    testImplementation group: 'org.powermock', name: 'powermock-api-mockito2', version: '2.0.2'
-    testImplementation group: 'org.powermock', name: 'powermock-module-junit4', version: '2.0.2'
-    testImplementation group: 'org.powermock', name: 'powermock-module-junit4-common', version: '2.0.2'
-    testImplementation group: 'org.powermock', name: 'powermock-core', version: '2.0.2'
-    testImplementation group: 'org.powermock', name: 'powermock-api-support', version: '2.0.2'
-    testImplementation group: 'org.powermock', name: 'powermock-reflect', version: '2.0.2'
-    testImplementation group: 'org.objenesis', name: 'objenesis', version: '3.0.1'
-    testImplementation group: 'net.bytebuddy', name: 'byte-buddy', version: '1.9.15'
-    testImplementation group: 'net.bytebuddy', name: 'byte-buddy-agent', version: '1.9.15'
+    testImplementation group: 'org.mockito', name: 'mockito-core', version: '5.9.0'
+    testImplementation group: 'org.objenesis', name: 'objenesis', version: '3.3'
+    testImplementation group: 'net.bytebuddy', name: 'byte-buddy', version: '1.14.9'
+    testImplementation group: 'net.bytebuddy', name: 'byte-buddy-agent', version: '1.14.9'
     testCompileOnly 'org.apiguardian:apiguardian-api:1.1.0'
-    testImplementation 'org.junit.jupiter:junit-jupiter-api:5.7.2'
-    testImplementation  'org.junit.jupiter:junit-jupiter-params:5.7.2'
-    testImplementation 'org.junit.jupiter:junit-jupiter-engine:5.7.2'
-    testRuntimeOnly 'org.junit.vintage:junit-vintage-engine:5.7.2'
+    testImplementation 'org.junit.jupiter:junit-jupiter-api:5.8.2'
+    testImplementation  'org.junit.jupiter:junit-jupiter-params:5.8.2'
+    testImplementation 'org.junit.jupiter:junit-jupiter-engine:5.8.2'
+    testRuntimeOnly 'org.junit.vintage:junit-vintage-engine:5.8.2'
     testCompileOnly 'junit:junit:4.13.2'
 }
 
 compileJava.options.compilerArgs << "-Xlint:-deprecation,-rawtypes,-serial,-try,-unchecked"
 
-test {
-    useJUnitPlatform()
-}
-
-apply plugin: 'nebula.ospackage'
+apply plugin: 'com.netflix.nebula.ospackage'
 
 // This is afterEvaluate because the bundlePlugin ZIP task is updated afterEvaluate and changes the ZIP name to match the plugin name
 afterEvaluate {
@@ -838,9 +830,8 @@ afterEvaluate {
         task renameRpm(type: Copy) {
             from("$buildDir/distributions")
             into("$buildDir/distributions")
-            include archiveName
-            rename archiveName, "${packageName}-${version}.rpm"
-            doLast { delete file("$buildDir/distributions/$archiveName") }
+            rename "$archiveFileName", "${packageName}-${archiveVersion}.rpm"
+            doLast { delete file("$buildDir/distributions/$archiveFileName") }
         }
     }
 
@@ -851,9 +842,8 @@ afterEvaluate {
         task renameDeb(type: Copy) {
             from("$buildDir/distributions")
             into("$buildDir/distributions")
-            include archiveName
-            rename archiveName, "${packageName}-${version}.deb"
-            doLast { delete file("$buildDir/distributions/$archiveName") }
+            rename "$archiveFileName", "${packageName}-${archiveVersion}.deb"
+            doLast { delete file("$buildDir/distributions/$archiveFileName") }
         }
     }
 
diff --git a/gradle/wrapper/gradle-wrapper.jar b/gradle/wrapper/gradle-wrapper.jar
index 943f0cbfa..7f93135c4 100644
Binary files a/gradle/wrapper/gradle-wrapper.jar and b/gradle/wrapper/gradle-wrapper.jar differ
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index 508322917..3499ded5c 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -1,6 +1,6 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-7.6.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.5-bin.zip
 networkTimeout=10000
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
diff --git a/gradlew b/gradlew
index 65dcd68d6..1aa94a426 100755
--- a/gradlew
+++ b/gradlew
@@ -83,10 +83,8 @@ done
 # This is normally unused
 # shellcheck disable=SC2034
 APP_BASE_NAME=${0##*/}
-APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit
-
-# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
-DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+# Discard cd standard output in case $CDPATH is set (https://github.com/gradle/gradle/issues/25036)
+APP_HOME=$( cd "${APP_HOME:-./}" > /dev/null && pwd -P ) || exit
 
 # Use the maximum available, or set MAX_FD != -1 to use that value.
 MAX_FD=maximum
@@ -133,10 +131,13 @@ location of your Java installation."
     fi
 else
     JAVACMD=java
-    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+    if ! command -v java >/dev/null 2>&1
+    then
+        die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
 
 Please set the JAVA_HOME variable in your environment to match the
 location of your Java installation."
+    fi
 fi
 
 # Increase the maximum file descriptors if we can.
@@ -144,7 +145,7 @@ if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
     case $MAX_FD in #(
       max*)
         # In POSIX sh, ulimit -H is undefined. That's why the result is checked to see if it worked.
-        # shellcheck disable=SC3045 
+        # shellcheck disable=SC2039,SC3045
         MAX_FD=$( ulimit -H -n ) ||
             warn "Could not query maximum file descriptor limit"
     esac
@@ -152,7 +153,7 @@ if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
       '' | soft) :;; #(
       *)
         # In POSIX sh, ulimit -n is undefined. That's why the result is checked to see if it worked.
-        # shellcheck disable=SC3045 
+        # shellcheck disable=SC2039,SC3045
         ulimit -n "$MAX_FD" ||
             warn "Could not set maximum file descriptor limit to $MAX_FD"
     esac
@@ -197,11 +198,15 @@ if "$cygwin" || "$msys" ; then
     done
 fi
 
-# Collect all arguments for the java command;
-#   * $DEFAULT_JVM_OPTS, $JAVA_OPTS, and $GRADLE_OPTS can contain fragments of
-#     shell script including quotes and variable substitutions, so put them in
-#     double quotes to make sure that they get re-expanded; and
-#   * put everything else in single quotes, so that it's not re-expanded.
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Collect all arguments for the java command:
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, JAVA_OPTS, and optsEnvironmentVar are not allowed to contain shell fragments,
+#     and any embedded shellness will be escaped.
+#   * For example: A user cannot expect ${Hostname} to be expanded, as it is an environment variable and will be
+#     treated as '${Hostname}' itself on the command line.
 
 set -- \
         "-Dorg.gradle.appname=$APP_BASE_NAME" \
diff --git a/src/test/java/org/opensearch/ad/NodeStateManagerTests.java b/src/test/java/org/opensearch/ad/NodeStateManagerTests.java
index 8e0152096..1924e7cfe 100644
--- a/src/test/java/org/opensearch/ad/NodeStateManagerTests.java
+++ b/src/test/java/org/opensearch/ad/NodeStateManagerTests.java
@@ -11,12 +11,12 @@
 
 package org.opensearch.ad;
 
-import static org.mockito.Matchers.any;
+import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
-import static org.mockito.Mockito.verifyZeroInteractions;
+import static org.mockito.Mockito.verifyNoInteractions;
 import static org.mockito.Mockito.when;
 import static org.opensearch.ad.settings.AnomalyDetectorSettings.BACKOFF_MINUTES;
 import static org.opensearch.ad.settings.AnomalyDetectorSettings.MAX_RETRY_FOR_UNRESPONSIVE_NODE;
@@ -232,7 +232,7 @@ public void testShouldMute() {
     public void testMaintenanceDoNothing() {
         stateManager.maintenance();
 
-        verifyZeroInteractions(clock);
+        verifyNoInteractions(clock);
     }
 
     public void testHasRunningQuery() throws IOException {
diff --git a/src/test/java/org/opensearch/ad/TestHelpers.java b/src/test/java/org/opensearch/ad/TestHelpers.java
index 3c3acbfcb..ea0109e68 100644
--- a/src/test/java/org/opensearch/ad/TestHelpers.java
+++ b/src/test/java/org/opensearch/ad/TestHelpers.java
@@ -12,14 +12,14 @@
 package org.opensearch.ad;
 
 import static org.apache.http.entity.ContentType.APPLICATION_JSON;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
 import static org.opensearch.ad.model.AnomalyDetectorJob.ANOMALY_DETECTOR_JOB_INDEX;
 import static org.opensearch.cluster.node.DiscoveryNodeRole.BUILT_IN_ROLES;
 import static org.opensearch.core.xcontent.XContentParserUtils.ensureExpectedToken;
 import static org.opensearch.index.query.AbstractQueryBuilder.parseInnerQueryBuilder;
 import static org.opensearch.index.seqno.SequenceNumbers.UNASSIGNED_SEQ_NO;
 import static org.opensearch.test.OpenSearchTestCase.*;
-import static org.powermock.api.mockito.PowerMockito.mock;
-import static org.powermock.api.mockito.PowerMockito.when;
 
 import java.io.IOException;
 import java.nio.ByteBuffer;
diff --git a/src/test/java/org/opensearch/ad/cluster/ADClusterEventListenerTests.java b/src/test/java/org/opensearch/ad/cluster/ADClusterEventListenerTests.java
index 1a51cb9be..6f30ed118 100644
--- a/src/test/java/org/opensearch/ad/cluster/ADClusterEventListenerTests.java
+++ b/src/test/java/org/opensearch/ad/cluster/ADClusterEventListenerTests.java
@@ -13,7 +13,7 @@
 
 import static java.util.Collections.emptyMap;
 import static java.util.Collections.emptySet;
-import static org.mockito.Matchers.any;
+import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.mock;
 import static org.opensearch.cluster.node.DiscoveryNodeRole.BUILT_IN_ROLES;
diff --git a/src/test/java/org/opensearch/ad/feature/FeatureManagerTests.java b/src/test/java/org/opensearch/ad/feature/FeatureManagerTests.java
index a46e4b897..c8d2991ab 100644
--- a/src/test/java/org/opensearch/ad/feature/FeatureManagerTests.java
+++ b/src/test/java/org/opensearch/ad/feature/FeatureManagerTests.java
@@ -19,8 +19,8 @@
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyBoolean;
 import static org.mockito.ArgumentMatchers.anyLong;
-import static org.mockito.Matchers.argThat;
-import static org.mockito.Matchers.eq;
+import static org.mockito.ArgumentMatchers.argThat;
+import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.doThrow;
 import static org.mockito.Mockito.mock;
diff --git a/src/test/java/org/opensearch/ad/feature/SearchFeatureDaoParamTests.java b/src/test/java/org/opensearch/ad/feature/SearchFeatureDaoParamTests.java
index 67d706159..b9f35dc0d 100644
--- a/src/test/java/org/opensearch/ad/feature/SearchFeatureDaoParamTests.java
+++ b/src/test/java/org/opensearch/ad/feature/SearchFeatureDaoParamTests.java
@@ -82,13 +82,6 @@
 import org.opensearch.search.aggregations.metrics.Percentile;
 import org.opensearch.search.builder.SearchSourceBuilder;
 import org.opensearch.threadpool.ThreadPool;
-import org.powermock.api.mockito.PowerMockito;
-import org.powermock.core.classloader.annotations.PowerMockIgnore;
-import org.powermock.core.classloader.annotations.PrepareForTest;
-import org.powermock.modules.junit4.PowerMockRunner;
-import org.powermock.modules.junit4.PowerMockRunnerDelegate;
-
-import com.google.gson.Gson;
 
 /**
  * Due to https://tinyurl.com/2y265s2w, tests with and without @Parameters annotation
@@ -96,10 +89,7 @@
  * while SearchFeatureDaoTests do not use @Parameters.
  *
  */
-@PowerMockIgnore("javax.management.*")
-@RunWith(PowerMockRunner.class)
-@PowerMockRunnerDelegate(JUnitParamsRunner.class)
-@PrepareForTest({ ParseUtils.class, Gson.class })
+@RunWith(JUnitParamsRunner.class)
 public class SearchFeatureDaoParamTests {
 
     private SearchFeatureDao searchFeatureDao;
@@ -156,7 +146,6 @@ public class SearchFeatureDaoParamTests {
     @Before
     public void setup() throws Exception {
         MockitoAnnotations.initMocks(this);
-        PowerMockito.mockStatic(ParseUtils.class);
 
         interpolator = new LinearUniformInterpolator(new SingleFeatureLinearUniformInterpolator());
 
@@ -233,14 +222,13 @@ public void getFeaturesForPeriod_returnExpectedToListener(List<Aggregation> aggs
 
         long start = 100L;
         long end = 200L;
-        when(ParseUtils.generateInternalFeatureQuery(eq(detector), eq(start), eq(end), eq(xContent))).thenReturn(searchSourceBuilder);
         when(searchResponse.getAggregations()).thenReturn(new Aggregations(aggs));
         when(detector.getEnabledFeatureIds()).thenReturn(featureIds);
         doAnswer(invocation -> {
             ActionListener<SearchResponse> listener = invocation.getArgument(1);
             listener.onResponse(searchResponse);
             return null;
-        }).when(client).search(eq(searchRequest), any(ActionListener.class));
+        }).when(client).search(any(SearchRequest.class), any(ActionListener.class));
 
         ActionListener<Optional<double[]>> listener = mock(ActionListener.class);
         searchFeatureDao.getFeaturesForPeriod(detector, start, end, listener);
diff --git a/src/test/java/org/opensearch/ad/feature/SearchFeatureDaoTests.java b/src/test/java/org/opensearch/ad/feature/SearchFeatureDaoTests.java
index a85f9cbcd..365b5064c 100644
--- a/src/test/java/org/opensearch/ad/feature/SearchFeatureDaoTests.java
+++ b/src/test/java/org/opensearch/ad/feature/SearchFeatureDaoTests.java
@@ -12,6 +12,7 @@
 package org.opensearch.ad.feature;
 
 import static java.util.Arrays.asList;
+import static java.util.Collections.emptyMap;
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.core.AnyOf.anyOf;
 import static org.hamcrest.core.IsInstanceOf.instanceOf;
@@ -90,6 +91,7 @@
 import org.opensearch.search.aggregations.AggregatorFactories;
 import org.opensearch.search.aggregations.InternalAggregations;
 import org.opensearch.search.aggregations.bucket.MultiBucketsAggregation;
+import org.opensearch.search.aggregations.metrics.InternalMax;
 import org.opensearch.search.aggregations.metrics.InternalMin;
 import org.opensearch.search.aggregations.metrics.InternalTDigestPercentiles;
 import org.opensearch.search.aggregations.metrics.Max;
@@ -98,14 +100,7 @@
 import org.opensearch.search.aggregations.metrics.Percentile;
 import org.opensearch.search.builder.SearchSourceBuilder;
 import org.opensearch.threadpool.ThreadPool;
-import org.powermock.api.mockito.PowerMockito;
-import org.powermock.core.classloader.annotations.PowerMockIgnore;
-import org.powermock.core.classloader.annotations.PrepareForTest;
-import org.powermock.modules.junit4.PowerMockRunner;
-
-@PowerMockIgnore("javax.management.*")
-@RunWith(PowerMockRunner.class)
-@PrepareForTest({ ParseUtils.class })
+
 public class SearchFeatureDaoTests {
     private SearchFeatureDao searchFeatureDao;
 
@@ -159,8 +154,7 @@ public class SearchFeatureDaoTests {
     @Before
     public void setup() throws Exception {
         MockitoAnnotations.initMocks(this);
-        PowerMockito.mockStatic(ParseUtils.class);
-
+        
         interpolator = new LinearUniformInterpolator(new SingleFeatureLinearUniformInterpolator());
 
         ExecutorService executorService = mock(ExecutorService.class);
@@ -265,7 +259,10 @@ public void getLatestDataTime_returnExpectedToListener() {
             return null;
         }).when(client).search(eq(searchRequest), any(ActionListener.class));
 
-        when(ParseUtils.getLatestDataTime(eq(searchResponse))).thenReturn(Optional.of(epochTime));
+        InternalMax maxAgg = new InternalMax(CommonName.AGG_NAME_MAX_TIME, epochTime, DocValueFormat.RAW, emptyMap());
+        InternalAggregations internalAggregations = InternalAggregations.from(Collections.singletonList(maxAgg));
+        when(searchResponse.getAggregations()).thenReturn(internalAggregations);
+
         ActionListener<Optional<Long>> listener = mock(ActionListener.class);
         searchFeatureDao.getLatestDataTime(detector, listener);
 
@@ -296,13 +293,12 @@ public void getFeaturesForPeriod_throwToListener_whenResponseParsingFails() thro
 
         long start = 100L;
         long end = 200L;
-        when(ParseUtils.generateInternalFeatureQuery(eq(detector), eq(start), eq(end), eq(xContent))).thenReturn(searchSourceBuilder);
         when(detector.getEnabledFeatureIds()).thenReturn(null);
         doAnswer(invocation -> {
             ActionListener<SearchResponse> listener = invocation.getArgument(1);
             listener.onResponse(searchResponse);
             return null;
-        }).when(client).search(eq(searchRequest), any(ActionListener.class));
+        }).when(client).search(any(SearchRequest.class), any(ActionListener.class));
 
         ActionListener<Optional<double[]>> listener = mock(ActionListener.class);
         searchFeatureDao.getFeaturesForPeriod(detector, start, end, listener);
@@ -316,12 +312,11 @@ public void getFeaturesForPeriod_throwToListener_whenSearchFails() throws Except
 
         long start = 100L;
         long end = 200L;
-        when(ParseUtils.generateInternalFeatureQuery(eq(detector), eq(start), eq(end), eq(xContent))).thenReturn(searchSourceBuilder);
         doAnswer(invocation -> {
             ActionListener<SearchResponse> listener = invocation.getArgument(1);
             listener.onFailure(new RuntimeException());
             return null;
-        }).when(client).search(eq(searchRequest), any(ActionListener.class));
+        }).when(client).search(any(SearchRequest.class), any(ActionListener.class));
 
         ActionListener<Optional<double[]>> listener = mock(ActionListener.class);
         searchFeatureDao.getFeaturesForPeriod(detector, start, end, listener);
diff --git a/src/test/java/org/opensearch/ad/ml/CheckpointDaoTests.java b/src/test/java/org/opensearch/ad/ml/CheckpointDaoTests.java
index c41b94e10..9a8874610 100644
--- a/src/test/java/org/opensearch/ad/ml/CheckpointDaoTests.java
+++ b/src/test/java/org/opensearch/ad/ml/CheckpointDaoTests.java
@@ -12,7 +12,7 @@
 package org.opensearch.ad.ml;
 
 import static org.mockito.ArgumentMatchers.eq;
-import static org.mockito.Matchers.any;
+import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.doReturn;
 import static org.mockito.Mockito.doThrow;
diff --git a/src/test/java/org/opensearch/ad/ml/ModelManagerTests.java b/src/test/java/org/opensearch/ad/ml/ModelManagerTests.java
index d16776fe2..e6b0e460b 100644
--- a/src/test/java/org/opensearch/ad/ml/ModelManagerTests.java
+++ b/src/test/java/org/opensearch/ad/ml/ModelManagerTests.java
@@ -17,7 +17,7 @@
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyLong;
 import static org.mockito.ArgumentMatchers.anyString;
-import static org.mockito.Matchers.eq;
+import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.doThrow;
 import static org.mockito.Mockito.mock;
diff --git a/src/test/java/org/opensearch/ad/transport/GetAnomalyDetectorActionTests.java b/src/test/java/org/opensearch/ad/transport/GetAnomalyDetectorActionTests.java
index 60144c63c..3f51105dc 100644
--- a/src/test/java/org/opensearch/ad/transport/GetAnomalyDetectorActionTests.java
+++ b/src/test/java/org/opensearch/ad/transport/GetAnomalyDetectorActionTests.java
@@ -12,29 +12,43 @@
 package org.opensearch.ad.transport;
 
 import java.io.IOException;
+import java.util.Collection;
+import java.util.List;
 
 import org.junit.Assert;
-import org.junit.Before;
 import org.junit.Test;
-import org.junit.runner.RunWith;
 import org.mockito.Mockito;
+import org.opensearch.ad.AnomalyDetectorPlugin;
+import org.opensearch.ad.TestHelpers;
 import org.opensearch.ad.model.ADTask;
 import org.opensearch.ad.model.AnomalyDetector;
 import org.opensearch.ad.model.AnomalyDetectorJob;
 import org.opensearch.ad.model.DetectorProfile;
+import org.opensearch.ad.model.Feature;
 import org.opensearch.common.io.stream.BytesStreamOutput;
+import org.opensearch.core.common.io.stream.NamedWriteableAwareStreamInput;
+import org.opensearch.core.common.io.stream.NamedWriteableRegistry;
 import org.opensearch.core.common.io.stream.StreamInput;
 import org.opensearch.core.rest.RestStatus;
-import org.powermock.api.mockito.PowerMockito;
-import org.powermock.core.classloader.annotations.PrepareForTest;
-import org.powermock.modules.junit4.PowerMockRunner;
+import org.opensearch.plugins.Plugin;
+import org.opensearch.test.InternalSettingsPlugin;
+import org.opensearch.test.OpenSearchSingleNodeTestCase;
 
-@RunWith(PowerMockRunner.class)
-@PrepareForTest(GetAnomalyDetectorResponse.class)
-public class GetAnomalyDetectorActionTests {
-    @Before
-    public void setUp() throws Exception {
+/**
+ * Need to extend from OpenSearchSingleNodeTestCase and override getPlugins and writeableRegistry
+ * for testGetResponse. Without it, we will have exception "can't read named writeable from StreamInput"
+ * when deserializing AnomalyDetector.
+ *
+ */
+public class GetAnomalyDetectorActionTests extends OpenSearchSingleNodeTestCase {
+    @Override
+    protected Collection<Class<? extends Plugin>> getPlugins() {
+        return pluginList(InternalSettingsPlugin.class, AnomalyDetectorPlugin.class);
+    }
 
+    @Override
+    protected NamedWriteableRegistry writableRegistry() {
+        return getInstanceFromNode(NamedWriteableRegistry.class);
     }
 
     @Test
@@ -51,9 +65,9 @@ public void testGetRequest() throws IOException {
     @Test
     public void testGetResponse() throws Exception {
         BytesStreamOutput out = new BytesStreamOutput();
-        AnomalyDetector detector = Mockito.mock(AnomalyDetector.class);
+        Feature feature = TestHelpers.randomFeature(true);
+        AnomalyDetector detector = TestHelpers.randomAnomalyDetector(List.of(feature));
         AnomalyDetectorJob detectorJob = Mockito.mock(AnomalyDetectorJob.class);
-        Mockito.doNothing().when(detector).writeTo(out);
         GetAnomalyDetectorResponse response = new GetAnomalyDetectorResponse(
             1234,
             "4567",
@@ -71,8 +85,8 @@ public void testGetResponse() throws Exception {
             false
         );
         response.writeTo(out);
-        StreamInput input = out.bytes().streamInput();
-        PowerMockito.whenNew(AnomalyDetector.class).withAnyArguments().thenReturn(detector);
+
+        NamedWriteableAwareStreamInput input = new NamedWriteableAwareStreamInput(out.bytes().streamInput(), writableRegistry());
         GetAnomalyDetectorResponse newResponse = new GetAnomalyDetectorResponse(input);
         Assert.assertNotNull(newResponse);
     }
diff --git a/src/test/java/org/opensearch/ad/transport/MultiEntityResultTests.java b/src/test/java/org/opensearch/ad/transport/MultiEntityResultTests.java
index a2404f72d..7e781fb94 100644
--- a/src/test/java/org/opensearch/ad/transport/MultiEntityResultTests.java
+++ b/src/test/java/org/opensearch/ad/transport/MultiEntityResultTests.java
@@ -16,7 +16,7 @@
 import static org.mockito.ArgumentMatchers.anyInt;
 import static org.mockito.ArgumentMatchers.anyString;
 import static org.mockito.ArgumentMatchers.eq;
-import static org.mockito.Matchers.argThat;
+import static org.mockito.ArgumentMatchers.argThat;
 import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.never;
diff --git a/src/test/java/org/opensearch/ad/transport/PreviewAnomalyDetectorTransportActionTests.java b/src/test/java/org/opensearch/ad/transport/PreviewAnomalyDetectorTransportActionTests.java
index f10b5ea49..5a0abbd62 100644
--- a/src/test/java/org/opensearch/ad/transport/PreviewAnomalyDetectorTransportActionTests.java
+++ b/src/test/java/org/opensearch/ad/transport/PreviewAnomalyDetectorTransportActionTests.java
@@ -14,7 +14,6 @@
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyInt;
 import static org.mockito.ArgumentMatchers.anyLong;
-import static org.mockito.ArgumentMatchers.anyObject;
 import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.doReturn;
 import static org.mockito.Mockito.mock;
@@ -185,7 +184,7 @@ public void onFailure(Exception e) {
             ActionListener<Features> listener = responseMock.getArgument(3);
             listener.onResponse(TestHelpers.randomFeatures());
             return null;
-        }).when(featureManager).getPreviewFeatures(anyObject(), anyLong(), anyLong(), any());
+        }).when(featureManager).getPreviewFeatures(any(), anyLong(), anyLong(), any());
         action.doExecute(task, request, previewResponse);
         assertTrue(inProgressLatch.await(100, TimeUnit.SECONDS));
     }
@@ -396,7 +395,7 @@ public void onFailure(Exception e) {
             ActionListener<Features> listener = responseMock.getArgument(3);
             listener.onResponse(TestHelpers.randomFeatures());
             return null;
-        }).when(featureManager).getPreviewFeatures(anyObject(), anyLong(), anyLong(), any());
+        }).when(featureManager).getPreviewFeatures(any(), anyLong(), anyLong(), any());
         action.doExecute(task, request, previewResponse);
         assertTrue(inProgressLatch.await(100, TimeUnit.SECONDS));
     }
diff --git a/src/test/java/org/opensearch/ad/util/ThrottlerTests.java b/src/test/java/org/opensearch/ad/util/ThrottlerTests.java
index ed2a6f710..63d060b28 100644
--- a/src/test/java/org/opensearch/ad/util/ThrottlerTests.java
+++ b/src/test/java/org/opensearch/ad/util/ThrottlerTests.java
@@ -12,7 +12,7 @@
 package org.opensearch.ad.util;
 
 import static org.mockito.Mockito.mock;
-import static org.powermock.api.mockito.PowerMockito.when;
+import static org.mockito.Mockito.when;
 
 import java.time.Clock;