@Test
public void shouldReturnContains() {

    fruits.add(orange);
    fruits.add(banana);
    fruits.add(waterMelon);
    assertTrue(fruits.contains(banana));
    assertFalse(fruits.contains(melon));
    assertTrue(fruits.containsAll(Arrays.asList(banana, orange)));
    assertFalse(fruits.containsAll(Arrays.asList(banana, melon)));
}