public void IntersectionWithTest() { MySet <string> s = new MySet <string>(); s.Add("a"); s.Add("b"); MySet <string> c = new MySet <string>(); c.Add("a"); c.Add("b"); c.Add("c"); var actual = c.IntersectionWith(s); Assert.IsTrue(actual.Contains("a") & actual.Contains("b")); }