// Test Expectations
// =====================================================================
RemovalListenerList list = new RemovalListenerList();
list.addListener(listenerMock1);
try {
list.addListener(listenerMock1);
fail("Did not detect attempt to add same listener twice");
} catch (IllegalStateException expected) {
assertEquals("Listener " + listenerMock1 +
" has already been added", expected.getMessage());
}