MSTestExecutionSubject.cs

public class MSTestExecutionSubject : ITestExecutionSubject
{
    private readonly List<ITestBehaviorObserver> testBehaviorObservers;

    public MSTestExecutionSubject()
    {
        this.testBehaviorObservers = new List<ITestBehaviorObserver>();
    }

    public void Attach(ITestBehaviorObserver observer)
    {
        testBehaviorObservers.Add(observer);
    }

    public void Detach(ITestBehaviorObserver observer)
    {
        testBehaviorObservers.Remove(observer);
    }

    public void PreTestInit(TestContext context, MemberInfo memberInfo)
    {
        foreach (var currentObserver in this.testBehaviorObservers)
        {
            currentObserver.PreTestInit(context, memberInfo);
        }
    }
    public void PostTestInit(TestContext context, MemberInfo memberInfo)
    {
        foreach (var currentObserver in this.testBehaviorObservers)
        {
            currentObserver.PostTestInit(context, memberInfo);
        }
    }

    public void PreTestCleanup(TestContext context, MemberInfo memberInfo)
    {
        foreach (var currentObserver in this.testBehaviorObservers)
        {
            currentObserver.PreTestCleanup(context, memberInfo);
        }
    }

    public void PostTestCleanup(TestContext context, MemberInfo memberInfo)
    {
        foreach (var currentObserver in this.testBehaviorObservers)
        {
            currentObserver.PostTestCleanup(context, memberInfo);
        }
    }

    public void TestInstantiated(MemberInfo memberInfo)
    {
        foreach (var currentObserver in this.testBehaviorObservers)
        {
            currentObserver.TestInstantiated(memberInfo);
        }
    }
}