xUnit.net - run code once before and after ALL tes

问题:

TL;DR - I'm looking for xUnit's equivalent of MSTest's AssemblyInitialize (aka the ONE feature it has that I like).

Specifically I'm looking for it because I have some Selenium smoke tests which I would like to be able to run with no other dependencies. I have a Fixture that will launch IisExpress for me and kill it on disposal. But doing this before every test hugely bloats runtime.

I would like to trigger this code once at the start of testing, and dispose of it (shutting down the process) at the end. How could I go about doing that?

Even if I can get programmatic access to something like "how many tests are currently being run" I can figure something out.

回答1:

As of Nov 2015 xUnit 2 is out, so there is a canonical way to share features between tests. It is documented here.

Basically you'll need to create a class doing the fixture:

    public class DatabaseFixture : IDisposable
    {
        public DatabaseFixture()
        {
            Db = new SqlConnection("MyConnectionString");

            // ... initialize data in the test database ...
        }

        public void Dispose()
        {
            // ... clean up test data from the database ...
        }

        public SqlConnection Db { get; private set; }
    }

A dummy class bearing the CollectionDefinition attribute. This class allows Xunit to create a test collection, and will use the given fixture for all test classes of the collection.

    [CollectionDefinition("Database collection")]
    public class DatabaseCollection : ICollectionFixture<DatabaseFixture>
    {
        // This class has no code, and is never created. Its purpose is simply
        // to be the place to apply [CollectionDefinition] and all the
        // ICollectionFixture<> interfaces.
    }

Then you need to add the collection name over all your test classes. The test classes can receive the fixture through the constructor.

    [Collection("Database collection")]
    public class DatabaseTestClass1
    {
        DatabaseFixture fixture;

        public DatabaseTestClass1(DatabaseFixture fixture)
        {
            this.fixture = fixture;
        }
    }

It's a bit more verbose than MsTests AssemblyInitialize since you have to declare on each test class which test collection it belongs, but it's also more modulable (and with MsTests you still need to put a TestClass on your classes)

Note: the samples have been taken from the documentation.

回答2:

Create a static field and implement a finalizer.

You can use the fact that xUnit creates an AppDomain to run your test assembly and unloads it when it's finished. Unloading the app domain will cause the finalizer to run.

I am using this method to start and stop IISExpress.

public sealed class ExampleFixture
{
    public static ExampleFixture Current = new ExampleFixture();

    private ExampleFixture()
    {
        // Run at start
    }

    ~ExampleFixture()
    {
        Dispose();
    }

    public void Dispose()
    {
        GC.SuppressFinalize(this);

        // Run at end
    }        
}

Edit: Access the fixture using ExampleFixture.Current in your tests.

回答3:

It's not possible to do in the framework today. This is a feature planned for 2.0.

In order to make this work before 2.0, it would require you to perform significant re-architecture on the framework, or write your own runners that recognized your own special attributes.

回答4:

To execute code on assembly initialize, then one can do this (Tested with xUnit 2.3.1)

using Xunit.Abstractions;
using Xunit.Sdk;

[assembly: Xunit.TestFramework("MyNamespace.MyClassName", "MyAssemblyName")]

namespace MyNamespace
{   
   public class MyClassName : XunitTestFramework
   {
      public MyClassName(IMessageSink messageSink)
        :base(messageSink)
      {
        // Place initialization code here
      }
   }
}

See also https://github.com/xunit/samples.xunit/tree/master/AssemblyFixtureExample

回答5:

I use AssemblyFixture (NuGet).

What it does is it provides an IAssemblyFixture<T> interface that is replacing any IClassFixture<T> where you want the object's lifetime to be as the testing assembly.

Example:

public class Singleton { }

public class TestClass1 : IAssemblyFixture<Singleton>
{
  readonly Singletone _Singletone;
  public TestClass1(Singleton singleton)
  {
    _Singleton = singleton;
  }

  [Fact]
  public void Test1()
  {
     //use singleton  
  }
}

public class TestClass2 : IAssemblyFixture<Singleton>
{
  readonly Singletone _Singletone;
  public TestClass2(Singleton singleton)
  {
    //same singleton instance of TestClass1
    _Singleton = singleton;
  }

  [Fact]
  public void Test2()
  {
     //use singleton  
  }
}

回答6:

Does your build tool provide such a feature?

In the Java world, when using Maven as a build tool, we use the appropriate phases of the build lifecycle. E.g. in your case (acceptance tests with Selenium-like tools), one can make good use of the pre-integration-test and post-integration-test phases to start/stop a webapp before/after one's integration-tests.

I'm pretty sure the same mechanism can be set up in your environment.

回答7:

You can use IUseFixture interface to make this happen. Also all of your test must inherit TestBase class. You can also use OneTimeFixture directly from your test.

public class TestBase : IUseFixture<OneTimeFixture<ApplicationFixture>>
{
    protected ApplicationFixture Application;

    public void SetFixture(OneTimeFixture<ApplicationFixture> data)
    {
        this.Application = data.Fixture;
    }
}

public class ApplicationFixture : IDisposable
{
    public ApplicationFixture()
    {
        // This code run only one time
    }

    public void Dispose()
    {
        // Here is run only one time too
    }
}

public class OneTimeFixture<TFixture> where TFixture : new()
{
    // This value does not share between each generic type
    private static readonly TFixture sharedFixture;

    static OneTimeFixture()
    {
        // Constructor will call one time for each generic type
        sharedFixture = new TFixture();
        var disposable = sharedFixture as IDisposable;
        if (disposable != null)
        {
            AppDomain.CurrentDomain.DomainUnload += (sender, args) => disposable.Dispose();
        }
    }

    public OneTimeFixture()
    {
        this.Fixture = sharedFixture;
    }

    public TFixture Fixture { get; private set; }
}

EDIT: Fix the problem that new fixture create for each test class.