feat: fix tests

Author: Piotr Stachaczynski

src/MaIN.Core.UnitTests/ChatContextTests.cs

@@ -82,9 +82,13 @@ public async Task CompleteAsync_ShouldCallChatService()
                 Content = "test-message"
             }
         };
+        
+
         _mockChatService.Setup(s => s.Completions(It.IsAny<Chat>(), It.IsAny<bool>(), It.IsAny<bool>(), null))
             .ReturnsAsync(chatResult);
 
+        _chatContext.WithMessage("User message");
+
         // Act
         var result = await _chatContext.CompleteAsync();
 

src/MaIN.Core/Hub/Contexts/ChatContext.cs

@@ -130,6 +130,10 @@ public async Task<ChatResult> CompleteAsync(
         bool interactive = false,
         Func<LLMTokenValue?, Task>? changeOfValue = null)
     {
+        if (_chat.Messages.Count == 0)
+        {
+            throw new InvalidOperationException("Chat has no messages."); //TODO good candidate for domain exception
+        }
         _chat.Messages.Last().Files = _files;
         if (!await ChatExists(_chat.Id))
         {