Mocking CompleteChatStreamingAsync

[ethan-christensen-cag]

Hello all,

I am just reaching out to see if there is any experience with mocking CompleteChatStreamingAsync with OpenAI Chat. I am wanting to test a service that utilizes OpenAI ChatClients CompleteChatStreamingAsync, though I can never seem to make it work.

My service consumes an instance of ChatClient which I am trying to Mock.

[Fact]
    public async Task StreamChatAsync_ShouldReturnStreamedContent()
    {
        // Arrange
        List<StreamingChatCompletionUpdate> mockStreamingChatCompletionUpdates =
        [
            OpenAIChatModelFactory.StreamingChatCompletionUpdate(contentUpdate: ["A"]),
            OpenAIChatModelFactory.StreamingChatCompletionUpdate(contentUpdate: ["B"]),
        ];
        
        _mockChatClient.Setup(client => client.CompleteChatStreamingAsync(It.IsAny<ChatMessage[]>(),
            It.IsAny<ChatCompletionOptions>(), 
            It.IsAny<CancellationToken>())
        ).Returns(mockStreamingChatCompletionUpdates.ToAsyncEnumerable());

        // Act
        var totalChunks = 0;
        var accumulatedContent = "";
        
        await foreach (var chunk in _openAiService.StreamChatAsync("Hello"))
        {
            totalChunks++;
            accumulatedContent += chunk;
        }
        
        // Assert
        totalChunks.Should().Be(2);
        accumulatedContent.Should().Be("AB");
    }

But am always having trouble mocking the streaming response with error:

Cannot resolve method:
    Returns(IAsyncEnumerable<StreamingChatCompletionUpdate>)
Candidates are:
    Returns(AsyncCollectionResult<StreamingChatCompletionUpdate>)
    Returns(Delegate)
    Returns(Func<AsyncCollectionResult<StreamingChatCompletionUpdate>>)
    Returns(InvocationFunc)
    all from interface IReturns<TMock,TResult>

with this section:

_mockChatClient.Setup(client => client.CompleteChatStreamingAsync(It.IsAny<ChatMessage[]>(),
            It.IsAny<ChatCompletionOptions>(), 
            It.IsAny<CancellationToken>())
        ).Returns(mockStreamingChatCompletionUpdates.ToAsyncEnumerable());