C# Unit Test open Window.xaml

I need to open my Window.xaml in Unit Test. I tried a simple code as follows:

 [Test]
 public void Test_window()
 {
      var mw = new MainWindow();
      mw.Show();
 }

The above code ends with an error.

The calling thread must be STA, because many UI components require this.

Afterwards, I tried the below code :

     [Test]
     public void Test_window()
     {
        Thread th = new Thread(new ThreadStart(delegate
        {
            var mw = new MainWindow();
            mw.Show();
        }));

        th.ApartmentState = ApartmentState.STA;
        th.Start();

     }

In this case , the test passes successfully, but no window is shown. Since I am new to WPF, it would be appreciable if any suggestions or guidance are available here.

Thanks.