### Question:
InMemoryStore implements ToDoStore { @Override public void delete(String id) { synchronized(store) { store.remove(id); } } InMemoryStore(); @Override Collection<ToDo> getAll(); @Override ToDo get(String id); @Override ToDo persist(ToDo td); @Override ToDo update(String id, ToDo td); @Override void delete(String id); @Override int count();  }### Answer:
@Test public void testDelete() throws Exception { emptyStore.delete("123"); populatedStore.delete(td1.getId()); assertNull(populatedStore.get(td1.getId())); }