Bug 236324 [Forms] Eclipse 3.4 crashes / failes to repaint when "Close Others" is used with SharedHeaderFormEditor
tests/org.eclipse.ui.tests.forms/forms/org/eclipse/ui/tests/forms/util/FormImagesTests.java
public void testSingleton() {
		Display display = Display.getCurrent();
		FormImages instance = FormImages.getInstance();
		
		Assert.assertTrue("getInstance() returned a different FormImages instance", instance.equals(FormImages.getInstance()));
		Image gradient = instance.getGradient(display, new Color(display, 1, 1, 1), new Color(display, 7, 7, 7), 21, 21, 0);
		instance.markFinished(gradient);
		
		Assert.assertTrue("getInstance() returned a different FormImages instance after creation and disposal of one image", instance.equals(FormImages.getInstance()));
	}
	
	public void testDisposeOne() {
		Display display = Display.getCurrent();
		Image gradient = FormImages.getInstance().getGradient(display, new Color(display, 255, 255, 255), new Color(display, 0, 0, 0), 21, 21, 0);
		FormImages.getInstance().markFinished(gradient);
		
		Assert.assertTrue("markFinished(...) did not dispose an image after a single getGradient()", gradient.isDisposed());
	}