Faking an Http response status

Faking an Http response status

What: A response was received but it was not an HTTP 200 OK.

Why: There's plenty of reasons why the response might be any number of HTTP Status codes, which are not HTTP 200 OK. Eg. An HTTP 500 SERVER ERROR or an Authentication problem which returns an HTTP 401 UNAUTHORISED ERROR, etc. An example why you should unit test for this is because imagine you require access to a locked down endpoint and your access token has expired, you might need to handle refreshing the access token and then re-attempting that data endpoint once more.

How: When we create the message handler, we set the HTTP Status we want to return.

How does this even work???: The trick was in our normal code where we call our endpoint ... we need to think about what happens when the result is not a 200 OK. In my unit tests, if it's not 200 OK I just throw an exception. You might want to do something more complex, like log this error, return a full error description and HTTP Status Code, etc.

    [Fact]
    public async Task GivenAServerError_GetSomeFooDataAsync_ThrowsAnException()
    {
        // Arrange.

        // Fake response.
        const string responseData = "Something Blew Up";
        var messageResponse = FakeHttpMessageHandler.GetStringHttpResponseMessage(responseData,
                                                                                    HttpStatusCode.InternalServerError);

        // Prepare our 'options' with all of the above fake stuff.
        var options = new HttpMessageOptions
        {
            HttpResponseMessage = messageResponse
        };
        var messageHandler = new FakeHttpMessageHandler(options);

        var myService = new MyService(messageHandler);

        // Act.
        // NOTE: network traffic will not leave your computer because you've faked the response, above.
        var result = await Should.ThrowAsync<InvalidOperationException>(myService.GetSomeFooDataAsync());

        // Assert.
        result.Message.ShouldStartWith(responseData);
    }