<PackageReference Include="NUnit" Version="4.2.1" />

NUnit.Framework.Internal.TestFixture

TestFixture is a surrogate for a user test fixture class, containing one or more tests.
namespace NUnit.Framework.Internal { public class TestFixture : TestSuite, IDisposableFixture { public LifeCycle LifeCycle { get; set; } public new ITypeInfo TypeInfo { get; } public TestFixture(ITypeInfo fixtureType, object[] arguments = null); public TestFixture(ITypeInfo fixtureType, Exception ex); } }