Bug 11863 Update Test Suite action does not allow to remove
What the action actually does is RECREATE the test suite based on the selection in the dialog. I do an update on a test suite which contains X. It is no clear that if I only select Y in the dialog that I'll end up with X being removed. Normally "Update" shows the content of the existing stuff (dir, zip) and allows to modify this. I think renaming the action (and the dialog) to Recreate Test Suite would solve the problem.
org.eclipse.jdt.junit/src/org/eclipse/jdt/junit/wizards/NewTestCaseCreationWizardPage.java
fMethodStubsButtons.setEnabled(3, true);
		String superClassName= getSuperClass();
		if (superClassName != null && !superClassName.equals("") && getPackageFragmentRoot() != null) { 
			try {
				IType type= NewTestCaseCreationWizardPage.resolveClassNameToType(getPackageFragmentRoot().getJavaProject(), getPackageFragment(), superClassName);
				JUnitStatus status = new JUnitStatus();				
				if (type == null) {
					status.setError(Messages.getString("NewTestClassWizPage.error.superclass.not_exist")); 
					fSuperClassStatus= status;
				} else {
					if (type.isInterface()) {
						status.setError(Messages.getString("NewTestClassWizPage.error.superclass.is_interface")); 
						fSuperClassStatus= status;
					}
					if (!TestSearchEngine.isTestImplementor(type)) {
						status.setError(Messages.getFormattedString("NewTestClassWizPage.error.superclass.not_implementing_test_interface", JUnitPlugin.TEST_INTERFACE_NAME)); 
						fSuperClassStatus= status;
					} else {
						IMethod setupMethod= type.getMethod(SETUP, new String[] {});
						IMethod teardownMethod= type.getMethod(TEARDOWN, new String[] {});
						if (setupMethod.exists())
							fMethodStubsButtons.setEnabled(2, !Flags.isFinal(setupMethod.getFlags()));
						if (teardownMethod.exists())
							fMethodStubsButtons.setEnabled(3, !Flags.isFinal(teardownMethod.getFlags()));
					}
				}
			} catch (JavaModelException e) {
				JUnitPlugin.log(e);
			}
		}