How to make sure that all the threads started by the test(s) are stopped before completion

Question

I am building a windows service that communicates with other processes using named pipe. My unit test for the named pipe communication is throwing this error message 4 times:

System.AppDomainUnloadedException: Attempted to access an unloaded AppDomain. This can happen if the test(s) started a thread but did not stop it. Make sure that all the threads started by the test(s) are stopped before completion.

Here's my unit test:

    [TestMethod]
    public void ListenToNamedPipeTest()
    {
        var watcher = new ManualResetEvent(false);

        var svc = new WindowService();
        svc.ClientMessageHandler += (connection, message) => watcher.Reset();
        svc.ListenToNamedPipe();
        sendMessageToNamedPipe("bla");
        var wait = watcher.WaitOne(1000);

        svc.Dispose();

        Assert.IsTrue(wait, "No messages received after 1 seconds");
    }

    private void sendMessageToNamedPipe(string text)
    {
        var client = new NamedPipeClient<Message, Message>(DeviceCertificateService.PIPE_NAME);
        client.ServerMessage += (conn, message) => Console.WriteLine("Server says: {0}", message.Text);

        // Start up the client asynchronously and connect to the specified server pipe.
        // This method will return immediately while the client runs in a separate background thread.
        client.Start();

        client.PushMessage(new Message { Text = text });

        client.Stop();
    }

How do I make all threads stop before my unit test stops?

Thanks

---

UPDATE:

The named pipe client does not have a close() function:

// Type: NamedPipeWrapper.NamedPipeClient`2
// Assembly: NamedPipeWrapper, Version=1.5.0.0, Culture=neutral, PublicKeyToken=null
// MVID: D2B99F4D-8C17-4DB6-8A02-29DCF82A4118
// Assembly location: C:\Users\Thang.Duong\Source\Workspaces\Post Tracking System\Applications\Dev\OHD\packages\NamedPipeWrapper.1.5.0\lib\net40\NamedPipeWrapper.dll

using System;

namespace NamedPipeWrapper
{
  public class NamedPipeClient<TRead, TWrite> where TRead : class where TWrite : class
  {
    public NamedPipeClient(string pipeName);
    public void Start();
    public void PushMessage(TWrite message);
    public void Stop();
    public void WaitForConnection();
    public void WaitForConnection(int millisecondsTimeout);
    public void WaitForConnection(TimeSpan timeout);
    public void WaitForDisconnection();
    public void WaitForDisconnection(int millisecondsTimeout);
    public void WaitForDisconnection(TimeSpan timeout);
    public bool AutoReconnect { get; set; }
    public event ConnectionMessageEventHandler<TRead, TWrite> ServerMessage;
    public event ConnectionEventHandler<TRead, TWrite> Disconnected;
    public event PipeExceptionEventHandler Error;
  }
}

Answer 1

My WindowsService inherits the ServiceBase class which has the Dispose() function to close all threads. That's why I get all racing errors.

I had to avoid calling Dispose() function and replace it with client.Close() and svc.Close() function. The svc.Close() function is my custom implementation to stop and close the named pipe server.