SimpleContainer implements Containerlike<T> { @Override public boolean offer(T o) { if (o == null) { throw new NullPointerException("parameter cannot be null"); } T thing = (T)o; if (this.canFit(thing)) { this.storage.add(thing); return true; } return false; } 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 offer(T)") public void testOffer() { Integer o = 0; SimpleContainer<Integer> instance = new SimpleContainer<>(); assertTrue(instance.offer(o)); instance.setVerifier(new SimpleIntegerCheck(1, 20)); assertTrue(instance.offer(1)); assertTrue(instance.offer(20)); assertFalse(instance.offer(0)); assertFalse(instance.offer(21)); }