Bug 329184 Detached view that is an activation target candidate can prevent perspective switching
1. Detach the 'Outline' view. 2. Window > Open Perspective > Debug 3. Window > Open Perspective > Java 4. The perspective switch doesn't actually happen. You see the 'Debug' perspective's content with an 'Outline' view detached. Closing the 'Outline' view in the 'Debug' perspective will workaround this problem.
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
private List<MPart> activatedParts = new ArrayList<MPart>();
		private List<MPart> deactivatedParts = new ArrayList<MPart>();
		private List<MPart> hiddenParts = new ArrayList<MPart>();
		private List<MPart> visibleParts = new ArrayList<MPart>();
		private int activated = 0;
		private int deactivated = 0;
		private int hidden = 0;
		private int visible = 0;
		private boolean valid = true;
		public void clear() {
			activated = 0;
			deactivated = 0;
			hidden = 0;
			visible = 0;
			activatedParts.clear();
			deactivatedParts.clear();
			hiddenParts.clear();
			visibleParts.clear();
			valid = true;
		}