SimpleContainer implements Containerlike<T> { @Override public boolean retainAll(Collection c) { return storage.retainAll(c); } SimpleContainer();  SimpleContainer(ThingTypeCheck<T> verifier);  SimpleContainer(ThingTypeCheck<T> verifier, int limit); @Override boolean canFit(T thing); @Override Collection<T> findSimilar(ThingTypeCheck<T>judge); @Override Collection<T> removeUnfit(); @Override boolean hasUnfit(); @Override void setVerifier(ThingTypeCheck<T> verifier); @Override ThingTypeCheck<T> getVerifier(); @Override boolean hasSizeLimit(); @Override int getSizeLimit(); @Override int setSizeLimit(int limit); @Override boolean add(T o); @Override boolean offer(T o); @Override int size(); @Override boolean isEmpty(); @Override boolean contains(Object o); @Override Iterator<T> iterator(); @Override T[] toArray(); @Override T[] toArray(T[] a); @Override boolean remove(Object o); @Override boolean containsAll(Collection c); @Override boolean addAll(Collection c); @Override boolean removeAll(Collection c); @Override boolean retainAll(Collection c); @Override void clear(); @Override boolean equals(Object obj); @Override int hashCode();  }
@Test @Covers("public boolean retainAll(Collection)") public void testRetainAll() { SimpleContainer<Integer> instance = new SimpleContainer<>(); Collection<Integer> c1 = new ArrayList<>(); c1.add(42); c1.add(1); Collection<Integer> c2 = new ArrayList<>(); c2.add(19); c2.add(0); assertTrue(instance.addAll(c1)); assertTrue(instance.containsAll(c1)); assertTrue(instance.addAll(c2)); assertTrue(instance.containsAll(c2)); assertTrue(instance.retainAll(c2)); assertFalse(instance.containsAll(c1)); assertTrue(instance.containsAll(c2)); }