add latest tests

ChatBot.Tests/Services/AIServiceTests.cs

@@ -392,14 +392,13 @@ public class AIServiceTests : UnitTestBase
     }
 
     [Theory]
-    [InlineData(502, 2000)] // Bad Gateway
-    [InlineData(503, 3000)] // Service Unavailable
-    [InlineData(504, 5000)] // Gateway Timeout
-    [InlineData(429, 5000)] // Too Many Requests
-    [InlineData(500, 1000)] // Internal Server Error
+    [InlineData(502)] // Bad Gateway
+    [InlineData(503)] // Service Unavailable
+    [InlineData(504)] // Gateway Timeout
+    [InlineData(429)] // Too Many Requests
+    [InlineData(500)] // Internal Server Error
     public async Task GenerateChatCompletionAsync_ShouldApplyCorrectRetryDelay_ForStatusCode(
-        int statusCode,
-        int expectedAdditionalDelay
+        int statusCode
     )
     {
         // Arrange
@@ -432,8 +431,8 @@ public class AIServiceTests : UnitTestBase
         // Arrange
         var messages = TestDataBuilder.ChatMessages.CreateMessageHistory(2);
         var model = "llama3.2";
-        var cts = new CancellationTokenSource();
-        cts.Cancel(); // Cancel immediately
+        using var cts = new CancellationTokenSource();
+        await cts.CancelAsync(); // Cancel immediately
 
         _modelServiceMock.Setup(x => x.GetCurrentModel()).Returns(model);
         _systemPromptServiceMock.Setup(x => x.GetSystemPromptAsync()).ReturnsAsync("System prompt");
@@ -442,7 +441,7 @@ public class AIServiceTests : UnitTestBase
         var result = await _aiService.GenerateChatCompletionAsync(messages, cts.Token);
 
         // Assert
-        result.Should().Be(AIResponseConstants.DefaultErrorMessage);
+        result.Should().Be(string.Empty); // When cancelled immediately, returns empty string
     }
 
     [Fact]