Using the HttpClientInterception to Test Methods That Use a HttpClient

Full source code available here.

In my previous post I showed a way of testing a controller that uses a HttpClient.

I had to mock the HttpMessageHandler pass that to the HttpClient and set a bunch of properties. It works well, but is a bit long winded.

I received a comment from a reader who suggested that I try the JustEat.HttpClientInterception library. It allows you to setup responses to specified requests, and pass these to a HttpClient. Then the HttpClient is passed to the controller.

Here is how the test method looks –

[Fact]
public async Task GetTest()
{
    //Arrange
    List<int> myList = new List<int>() {1, 2, 3, 4, 5};
    
    // setup the interceptor
    HttpRequestInterceptionBuilder builder = new HttpRequestInterceptionBuilder()
        .ForHost("localhost.something.com")
        .ForPath("/v1/numbers")
        .WithJsonContent(myList);
    
    // create the HttpClient from the builder
    // and setup the HttpClientBaseAddress
    HttpClient client = new HttpClientInterceptorOptions()
        .Register(builder).CreateHttpClient("http://localhost.something.com/v1/");

    ValuesController controller = new ValuesController(client);

    //Act
    IActionResult result = await controller.Get();

    //Assert
    OkObjectResult resultObject = result as OkObjectResult;
    Assert.NotNull(resultObject);

    List<int> numbers = resultObject.Value as List<int>;
    Assert.Equal(5, numbers.Count);
}

Briefly, here is the constructor of the values controller. It takes the HttpClient as a parameter, usually passed by dependency injection.

public class ValuesController : Controller
{
    readonly IAsyncPolicy<HttpResponseMessage> _httpRetryPolicy;
    private readonly HttpClient _httpClient;

    public ValuesController(HttpClient httpClient)
    {
        _httpClient = httpClient;
    }
	//snip..

Full source code available here.