There's no way to close the "JUnit Test Results" window. 

To reproduce:

1.- Run unit tests on any project. The window automagically appears in the IDE
as the main window (that's not very usable, the user has not requested to see
that window). 
2.- Close the "JUnit Test Results" window.
3.- Run unit tests again. The window appears again!!! In the middle of the
editor!! It shouldn't: the user has already closed it!
4.- Move the window down so that is beside the "Output" window.
5.- Run unit tests again.
6.- The window is there again!! It makes itself the main window, hiding the
"output window" I'm reading!!

Comment I:

The "JUnit Test Results" window should either disappear or be optional. Users
are used to use the "Output" window for watching output. There's no need to have
an additional "stubborn" window that keeps on appearing everywhere. 

Comment II:

There's no need to have a "JUnit Test Results" window at all. It's mere
existence is featuritis. Keep it simple.

Product details:

  Product Version       = NetBeans IDE Dev (Build 200508091556)
  Operating System      = Linux version 2.6.8.1-12mdk running on i386
  Java; VM; Vendor      = 1.5.0_04; Java HotSpot(TM) Client VM 1.5.0_04-b05; Sun
Microsystems Inc.
org.netbeans.modules.junit/2 [2.17 200508101800]