Enhance CustomException with flexible message handling and add tests

Author: davidwei

src/Api.Framework/Exceptions/CustomException.cs

@@ -2,9 +2,13 @@
 
 namespace Api.Framework.Exceptions;
 
-public class CustomException<T>(Exception? innerException = default)
-    : Exception("A custom exception happened", innerException)
+public class CustomException<T> : Exception
 {
+    public CustomException(string? message = null, Exception? innerException = null)
+        : base(message ?? innerException?.Message ?? "A custom exception happened", innerException)
+    {
+    }
+
     public FailedResult<T>? CustomData { get; set; }
 
     // Override ToString() method to provide more detailed exception information

src/Api.Framework/Helper/CustomExceptionHelper.cs

@@ -15,7 +15,7 @@ public static class CustomExceptionHelper
     public static CustomException<TData> New<TData>(TData data, string errorMessage, params object[] extraObjects)
     {
         var message = string.Format(errorMessage, extraObjects);
-        return new CustomException<TData>
+        return new CustomException<TData>(message)
         {
             CustomData = ResultHelper.New(data, FrameworkConstants.DefaultErrorCode, message)
         };
@@ -33,7 +33,7 @@ public static CustomException<TData> New<TData>(TData data, string errorMessage,
     public static CustomException<TData> New<TData>(TData data, int errorCode, string errorMessage, params object[] extraObjects)
     {
         var message = string.Format(errorMessage, extraObjects);
-        return new CustomException<TData>
+        return new CustomException<TData>(message)
         {
             CustomData = ResultHelper.New(data, errorCode, message)
         };

tests/Api.Framework.Tests/CustomExceptionTests.cs

@@ -0,0 +1,81 @@
+using Api.Framework.Exceptions;
+using Api.Framework.Helper;
+
+namespace Api.Framework.Tests;
+
+[TestFixture]
+public class CustomExceptionTests
+{
+    [Test]
+    public void CustomException_WithMessage_SetsCorrectExceptionMessage()
+    {
+        // Arrange
+        const string expectedMessage = "Test error message";
+
+        // Act
+        var exception = new CustomException<object>(expectedMessage);
+
+        // Assert
+        Assert.That(exception.Message, Is.EqualTo(expectedMessage));
+    }
+
+    [Test]
+    public void CustomException_WithNullMessage_UsesDefaultMessage()
+    {
+        // Arrange & Act
+        var exception = new CustomException<object>();
+
+        // Assert
+        Assert.That(exception.Message, Is.EqualTo("A custom exception happened"));
+    }
+
+    [Test]
+    public void CustomException_WithInnerExceptionButNoMessage_UsesInnerExceptionMessage()
+    {
+        // Arrange
+        const string innerMessage = "Inner exception message";
+        var innerException = new InvalidOperationException(innerMessage);
+
+        // Act
+        var exception = new CustomException<object>(null, innerException);
+
+        // Assert
+        Assert.That(exception.Message, Is.EqualTo(innerMessage));
+        Assert.That(exception.InnerException, Is.EqualTo(innerException));
+    }
+
+    [Test]
+    public void CustomExceptionHelper_New_CreatesExceptionWithCorrectMessage()
+    {
+        // Arrange
+        const string errorMessage = "Note with id {0} not found";
+        const long noteId = 123L;
+        const string expectedMessage = "Note with id 123 not found";
+
+        // Act
+        var exception = CustomExceptionHelper.New("test data", errorMessage, noteId);
+
+        // Assert
+        Assert.That(exception.Message, Is.EqualTo(expectedMessage));
+        Assert.That(exception.CustomData?.Message, Is.EqualTo(expectedMessage));
+    }
+
+    [Test]
+    public void CustomExceptionHelper_NewWithErrorCode_CreatesExceptionWithCorrectMessage()
+    {
+        // Arrange
+        const string errorMessage = "User {0} has {1} notes";
+        const int errorCode = 100;
+        const string userName = "testuser";
+        const int noteCount = 5;
+        const string expectedMessage = "User testuser has 5 notes";
+
+        // Act
+        var exception = CustomExceptionHelper.New("test data", errorCode, errorMessage, userName, noteCount);
+
+        // Assert
+        Assert.That(exception.Message, Is.EqualTo(expectedMessage));
+        Assert.That(exception.CustomData?.Message, Is.EqualTo(expectedMessage));
+        Assert.That(exception.CustomData?.ErrorCode, Is.EqualTo(errorCode));
+    }
+}