http typed client in net core unit testing

Question

How would i go about to unit test a service that makes calls to a http typed client? the examples given at https://docs.microsoft.com/en-us/aspnet/core/fundamentals/http-requests?view=aspnetcore-2.2#typed-clients do not use interface.

public GitHubService(HttpClient client)

Would creating interface for the typed client be needed for unit testing using xunit/moq? or wouldn't i need to unit test this service.

Norcino Norcino · Accepted Answer · 2019-06-10T13:36:38

I don't understand what you mean with

http typed client

but if like in the example, you want to test a class which uses HttpClient, either you create a wrapper for HttpClient and pass it's interface using dependency injection (so you can mock it), or you leverage the HttpResponseMessage constructor parameter of the HttpClient.

Make the HttpClient a constructor parameter and in the test create code like the following:

var mockHttpMessageHandler = new Mock<HttpMessageHandler>();
mockHttpMessageHandler.Protected()
   .Setup<Task<HttpResponseMessage>>(
      "SendAsync",
      ItExpr.IsAny<HttpRequestMessage>(), // Customise this as you want
      ItExpr.IsAny<CancellationToken>()
   )
   // Create the response you want to return
   .ReturnsAsync(new HttpResponseMessage()
   {    
      StatusCode = HttpStatusCode.OK,
      Content = new StringContent("[{'prop1': 100,'prop2': 'value'}]"),
   });

// Create an HttpClient using the mocked message handler
var httpClient = new HttpClient(mockHttpMessageHandler.Object)
{
   BaseAddress = new Uri("http://anyurl.com/"),
};

var testedService = new MyServiceUnderTest(httpClient);

var result = await testedService.MethodUnderTest(parameters [...]);

To simplify the setup of the moq, restricting the expected HttpRequestMessage, I use this helper method.

    /// <summary>
    /// Setup the mocked http handler with the specified criteria
    /// </summary>
    /// <param name="httpStatusCode">Desired status code returned in the response</param>
    /// <param name="jsonResponse">Desired Json response</param>
    /// <param name="httpMethod">Post, Get, Put ...</param>
    /// <param name="uriSelector">Function used to filter the uri for which the setup must be applied</param>
    /// <param name="bodySelector">Function used to filter the body of the requests for which the setup must be applied</param>
    private void SetupHttpMock(HttpStatusCode httpStatusCode, string jsonResponse, HttpMethod httpMethod, Func<string, bool> uriSelector, Func<string, bool> bodySelector = null)
    {
        if (uriSelector == null) uriSelector = (s) => true;
        if (bodySelector == null) bodySelector = (s) => true;

        _messageHandlerMock
            .Protected()
            .Setup<Task<HttpResponseMessage>>("SendAsync",
                ItExpr.Is<HttpRequestMessage>(m =>
                    m.Method == httpMethod &&
                    bodySelector(m.Content.ReadAsStringAsync().Result) &&
                    uriSelector(m.RequestUri.ToString())),
                ItExpr.IsAny<CancellationToken>())
            .ReturnsAsync(new HttpResponseMessage
            {
                StatusCode = httpStatusCode,
                Content = jsonResponse == null ? null : new StringContent(jsonResponse, Encoding.UTF8, "application/json")
            });
    }

http typed client in net core unit testing

2 Answers