add tests

ChatBot.Tests/Services/ChatServiceTests.cs

@@ -574,6 +574,74 @@ public class ChatServiceTests : UnitTestBase
         );
     }
 
+    [Fact]
+    public async Task ProcessMessageAsync_ShouldTrimHistory_WhenCompressionDisabled()
+    {
+        // Arrange
+        var chatId = 99999L;
+        _aiSettings.EnableHistoryCompression = false;
+
+        var session = TestDataBuilder.ChatSessions.CreateBasicSession(chatId);
+        session.MaxHistoryLength = 5; // force small history limit
+
+        _sessionStorageMock
+            .Setup(x => x.GetOrCreate(chatId, It.IsAny<string>(), It.IsAny<string>()))
+            .Returns(session);
+        _sessionStorageMock.Setup(x => x.Get(chatId)).Returns(session);
+        _aiServiceMock
+            .Setup(x =>
+                x.GenerateChatCompletionWithCompressionAsync(
+                    It.IsAny<List<ChatBot.Models.Dto.ChatMessage>>(),
+                    It.IsAny<CancellationToken>()
+                )
+            )
+            .ReturnsAsync("ok");
+
+        // Act: add many messages to exceed the limit
+        for (int i = 0; i < 10; i++)
+        {
+            await _chatService.ProcessMessageAsync(chatId, "u", $"m{i}");
+        }
+
+        // Assert: history trimmed to MaxHistoryLength
+        session.GetMessageCount().Should().BeLessThanOrEqualTo(5);
+    }
+
+    [Fact]
+    public async Task ProcessMessageAsync_ShouldCompressHistory_WhenCompressionEnabledAndThresholdExceeded()
+    {
+        // Arrange
+        var chatId = 88888L;
+        _aiSettings.EnableHistoryCompression = true;
+        _aiSettings.CompressionThreshold = 4;
+        _aiSettings.CompressionTarget = 3;
+
+        var session = TestDataBuilder.ChatSessions.CreateBasicSession(chatId);
+        session.MaxHistoryLength = 50; // avoid trimming impacting compression assertion
+
+        _sessionStorageMock
+            .Setup(x => x.GetOrCreate(chatId, It.IsAny<string>(), It.IsAny<string>()))
+            .Returns(session);
+        _sessionStorageMock.Setup(x => x.Get(chatId)).Returns(session);
+        _aiServiceMock
+            .Setup(x =>
+                x.GenerateChatCompletionWithCompressionAsync(
+                    It.IsAny<List<ChatBot.Models.Dto.ChatMessage>>(),
+                    It.IsAny<CancellationToken>()
+                )
+            )
+            .ReturnsAsync("ok");
+
+        // Act: add enough messages to exceed threshold
+        for (int i = 0; i < 6; i++)
+        {
+            await _chatService.ProcessMessageAsync(chatId, "u", $"m{i}");
+        }
+
+        // Assert: compressed to target (user+assistant messages should be around target)
+        session.GetMessageCount().Should().BeLessThanOrEqualTo(_aiSettings.CompressionTarget + 1);
+    }
+
     [Fact]
     public async Task ProcessMessageAsync_ShouldLogEmptyResponseMarker()
     {