How to quickly integration test in .NET

5-10-2023

I just saw this easy integration testing in .NET 6 on YouTube and was like: 'WOW! I want to try this out!' So I created a quick example and played around with it.

Testing an API endpoint

It revolves around an example by microsoft, simply testing an API endpoint. The pattern itself is much more powerful, but I am presenting an easy case here.

First add the next line to your Program.cs:

public partial class Program { }

Next create an integration test using whatever framework you like, and be in awe. Right... So this is the test I have written using xUnit:

[Fact]
public async Task Get_Request_ShouldReturnVersionString()
{
    // --arrange--
    
    var application = new WebApplicationFactory<Program>();
    var httpClient = application.CreateClient();
    
    // --act--
    
    var response = await httpClient.GetAsync("/v1/catalog");
    
    // --assert-- 
    
    Assert.IsTrue(response.IsSuccessStatusCode);
    Assert.AreEqual(HttpStatusCode.OK, response.StatusCode);
}

Program in WebApplicationFactory is pointing to the Program.cs of the API project you want to test. It tests a simple api endpoint returning only an OK result.

Let's run dotCover to see the results: What is happening?

As you can see, it actually tests (part of) the Program.cs for you! How nice! That is the effect of it being an integration test. And it is slow, certainly the way I have been setting things up now, which can be improved in the future.

Resources

Example code in HelmerDemo.WebshopDemo Catalog Service
Integration tests in ASP.NET Core
Web Application factory deep dive with Andrew Lock