Preconditions { public void addPrecondition(String precondition) { if (preconditions.add(precondition)) { dirty = true; } }  void addPrecondition(String precondition); void clearPreconditions(); void addCandidate(String candidate); void removeCandidate(String candidate); boolean areSatisfied(); @Override String toString();  }
@Test public void testAddPrecondition() { preconditions.addPrecondition("a"); assertFalse(preconditions.areSatisfied()); }