Share state between tests that run in parallel with XUnit.net

Question

I have a set of xunit.net tests that need to share state. Hopefully, I would like these tests to run in parallel. So I would want the runner to do:

• Create the shared fixture
• Run in parallel all the tests using that fixture

When reading the the xunit doc, it says that to share state between test classes, I need to define a 'collection fixture' and then but all my test classes into that new collection (ex: [Collection("Database collection")]). But when, I put my test class in the same fixture, they don't run in parallel anymore so it beats the purpose :(

Is there a built-in way to do what I want in XUnit?

My fallback will be to put my shared state into a static class.

Answer 1

You can extend xUnit using the AssemblyFixture example from the samples pasted below to create a fixture which can the accesses by tests while running in parallel.

Using this method the fixture is created before the tests and then injected into the tests which reference it. I use this to create a user which is then shared for that specific set run.

There is also a nuget package xunit.assemblyfixture:

using System;
using Xunit;

// The custom test framework enables the support
[assembly: TestFramework("AssemblyFixtureExample.XunitExtensions.XunitTestFrameworkWithAssemblyFixture", "AssemblyFixtureExample")]

// Add one of these for every fixture classes for the assembly.
// Just like other fixtures, you can implement IDisposable and it'll
// get cleaned up at the end of the test run.
[assembly: AssemblyFixture(typeof(MyAssemblyFixture))]

public class Sample1
{
    MyAssemblyFixture fixture;

    // Fixtures are injectable into the test classes, just like with class and collection fixtures
    public Sample1(MyAssemblyFixture fixture)
    {
        this.fixture = fixture;
    }

    [Fact]
    public void EnsureSingleton()
    {
        Assert.Equal(1, MyAssemblyFixture.InstantiationCount);
    }
}

public class Sample2
{
    MyAssemblyFixture fixture;

    public Sample2(MyAssemblyFixture fixture)
    {
        this.fixture = fixture;
    }

    [Fact]
    public void EnsureSingleton()
    {
        Assert.Equal(1, MyAssemblyFixture.InstantiationCount);
    }
}

public class MyAssemblyFixture : IDisposable
{
    public static int InstantiationCount;

    public MyAssemblyFixture()
    {
        InstantiationCount++;
    }

    public void Dispose()
    {
        // Uncomment this and it will surface as an assembly cleanup failure
        //throw new DivideByZeroException();
    }
}