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Integration tests ensure that an app's components function correctly at a level that includes the app's supporting infrastructure, such as the database, file system, and network. ASP.NET Core supports integration tests using a unit test framework with a test web host and an in-memory test server.¹

TestServer

Infrastructure components, such as the test web host and in-memory test server (TestServer), are provided or managed by the Microsoft.AspNetCore.Mvc.Testing package. Use of this package streamlines test creation and execution.¹

As it was said before, the TestServer class is used to create an in-memory test server we can use to perform requests. In order to get as close a possible to the real server, we can use the StartUp class from the ASP.NET Core project.

Integration test using TestServer

Using the TDD way of life 😉, we write the test first. To use TestServer, you first need to import Microsoft.AspNetCore.Mvc.Testing into your project.

public class SimpleTestServerIntegrationTest
{
    public HttpClient _client;

    public SimpleTestServerIntegrationTest()
    {
        var server = new TestServer(new WebHostBuilder().UseStartup<Startup>());
        _client = server.CreateClient();
    }

    [Fact]
    public async Task Description_NoCondition_Success()
    {
        var response = await _client.GetAsync("/Hello/World");
        response.EnsureSuccessStatusCode();

        var responseString = await response.Content.ReadAsStringAsync();

        Assert.Equal("Hello, World!", responseString);
    }
}

As you can see, we use the StartUp class from our main project. This is the same Startup class that is used in Program.cs. This way our tests uses the same configuration as our live server.

Next we get a client from the created server we can use to make a request.

Now that we have our failing test, it is time to write some code to make the test pass.

Controller implementation

public class HelloController : Controller
{
    public IActionResult Index()
    {
        return View();
    }

    public string World()
    {
        return "Hello, World!";
    }
}

By convention, ASP.NET core will use the controller name and the method name to build the URL. ² So this controller should be accessible with a URL http://localhost/Hello/World (Assuming your website is running on localhost). This is the path we set before in our integration test.

Running the test

When we fire up the test, it will run the TestServer using the configuration from Startup, create a client and send a request. When all is working as expected, your test should pass and you can move on to the next part of your application.