How to Unit Test Startup.cs in .NET Core

Question

How do people go about Unit Testing their Startup.cs classes in a .NET Core 2 application? All of the functionality seems to be provided by Static extensions methods which a

Answer 1

I also had a similar problem, but managed to get around that by using the WebHost in AspNetCore and essentially re-creating what program.cs does, and then Asserting that all of my services exist and are not null. You could go a step further and execute specific extensions for IServices with .ConfigureServices or actually perform operations with the services you created to make sure they were constructed properly.

One key, is I created a unit test startup class that inherits from the startup class I'm testing so that I don't have to worry about separate assemblies. You could use composition if you prefer to not use inheritance.

[TestClass]
public class StartupTests
{
    [TestMethod]
    public void StartupTest()
    {
        var webHost = Microsoft.AspNetCore.WebHost.CreateDefaultBuilder().UseStartup().Build();
        Assert.IsNotNull(webHost);
        Assert.IsNotNull(webHost.Services.GetRequiredService());
        Assert.IsNotNull(webHost.Services.GetRequiredService());
    }
}

public class Startup : MyStartup
{
    public Startup(IConfiguration config) : base(config) { }
}