@ContinuousIntegrationTest(estimatedDuration = 0.0)
 @Test(timeout = 300000)
 public void testAddVariableChangeListener() {
   // remove all observers, then add one new observer, and check if it can be removed without
   // exceptions.
   yoVariable.removeAllVariableChangedListeners();
   TestVariableChangedListener listener = new TestVariableChangedListener();
   yoVariable.addVariableChangedListener(listener);
   yoVariable.removeVariableChangedListener(listener);
 }
 private void addAllListenersToYoVariable() {
   for (TestVariableChangedListener observer : variableChangedListeners) {
     yoVariable.addVariableChangedListener(observer);
   }
 }