The same object instance is used when running tests in parallel

I recently switched from MsTest to Unit3 and I noticed that when my tests are running in parallel I receive the same hashcode for an object set up in [SetUp] method.

using System;
using System.Threading;
using NUnit.Framework;
[assembly: Parallelizable(ParallelScope.All)]
namespace Nunit3netcore
{
    public class User
    {

    }
    public class Tests
    {
        public User User { get; set; }

        [SetUp]
        public void Setup()
        {
            User = new User();
        }

        [Test]
        public void Test1()
        {
            Thread.Sleep(3000);
            TestContext.WriteLine(User.GetHashCode());
        }

        [Test]
        public void Test2()
        {
            Thread.Sleep(3000);
            TestContext.WriteLine(User.GetHashCode());

        }

        [Test]
        public void Test5()
        {

            Thread.Sleep(3000);
            TestContext.WriteLine(User.GetHashCode());
        }
    }
}

In test output for each test, I see that the hash code is the same. When I comment out assembly:Parralilzable attribute and my code is running in non-paralell the hash code is different for each test. In MsTest I was generated a new object with new hash code within [TestInitialize] method. Packages I use: Nunit 3.12.0 Nunit3TestAdapter 3.16.1 Microsoft.NET.Test.Sdk (16.5.0)

[rprouse]

When NUnit runs test in Parallel, it creates one instance of the test class and then calls each test method in parallel. So, what is happening is that Setup is being called multiple times creating and overwriting the User object then the tests all run using the last User created.

You can use thread local storage, or an easier fix is to add [FixtureLifeCycle(LifeCycle.InstancePerTestCase)] to the test class. If you do this, NUnit will create a new instance of your test class for each test method that is run.

See https://docs.nunit.org/articles/nunit/writing-tests/attributes/fixturelifecycle.html

[OsirisTerje]

The logger is just the small class above. It doesn’t contain anything suspicious. And the output from NUnit.Framework is on the other hand very suspicious. I think this issue should be transferred to the NUnit repro.