How to execute xUnit class tests in parallel using common fixture?

Question

I understand that by default xUnit will execute tasks within a class in series, but will execute tasks across classes in parallel.

I've created 3 test classes, but They each need common setup data (in a db - yes i know including a db is an unfortunate circumstance, but that inclusion can't change).

So to initialize the data set in the db, I created a fixture:

/// <summary> /// This fixture is used to initialize a known state of test data in the database /// </summary> public class DBFixture { /// <summary> /// Clear out and create new test data. Ensure we have a known state of input data. /// </summary> public DBFixture() { string script = File.ReadAllText("Database\\DataSetup.sql"); using (SqlConnection con = new SqlConnection(...)) { var result = con.QueryMultiple(script); } } }

Then to associate the fixture to multiple classes, I create a class that associates the fixture to a collection.

/// <summary> /// /// </summary> /// <see cref="https://xunit.net/docs/shared-context"/> [CollectionDefinition("My Collection")] public class MyCollection: ICollectionFixture<DBFixture> { // 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. //This class, and it's CollectionDefinition attribute tell the xUnit framework that any Test class that has a Collection attribute with the same collection name, will use the same instance of DBFixture. }

Then I create my test classes, with my tests, and associate them to my collection.

[Collection("My Collection")] public class MyTests { ... } [Collection("My Collection")] public class MyTests2 { ... }

When I run all my tests, there does not appear to be any parallelization, and I think it's because now all my test classes are part of the same collection. Is there a way to have a common fixture instance across test class & have parallel execution?

Have you taken a look at Collection Fixtures? xunit.net/docs/shared-context.html#collection-fixture — Shafiq Jetha
– Shafiq Jetha, Commented Mar 13, 2021 at 5:56
Yes, my example was taken from the doc you referenced. The link xunit.net/docs/running-tests-in-parallel.html says that "If we need to indicate that multiple test classes should not be run in parallel against one another, then we place them into the same test collection." but the collection fixture documentation xunit.net/docs/shared-context.html#collection-fixture says you need to put the tests in the same collection to use a common fixture. Looks like collection fixtures negate the ability to run classes in parallel. — Jeremy
– Jeremy, Commented Mar 15, 2021 at 3:11

Peter Csala · Accepted Answer · 2022-01-03 18:32:41Z

I use Assembly Fixture (Nuget)

Refer

public class TestClass : IAssemblyFixture<TestFixture> { private readonly TestFixture fixture; public MyTest(TestFixture fixture) { this.fixture = fixture; } [Fact] public void MyTest() { // test code here } }

Register TestFramework replacement in AssemblyInfo.cs file:

[assembly: TestFramework("Xunit.Extensions.Ordering.TestFramework", "Xunit.Extensions.Ordering")]

JoanComasFdz · Accepted Answer · 2025-04-08 19:23:39Z

Add the Meziantou.Xunit.ParallelTestFramework nuget package to your test project and all tests will run in parallel by default.

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