public void Should_be_possible_to_get_a_complement_between_two_sets_if_an_empty_set_was_informed() { IEnumerable<string> firstReferences = new List<string>() { "10", "20", "40", "60" }; IEnumerable<string> secondReferences = new List<string>(); SetOperation operation = new ComplementSetOperation(); IEnumerable<string> results = operation.Execute(firstReferences, secondReferences); Assert.AreEqual(4, results.Count()); string element = results.Where<string>(item => item == "10").SingleOrDefault(); Assert.IsNotNull(element, "the element expected is not exits"); element = results.Where<string>(item => item == "20").SingleOrDefault(); Assert.IsNotNull(element, "the element expected is not exits"); element = results.Where<string>(item => item == "40").SingleOrDefault(); Assert.IsNotNull(element, "the element expected is not exits"); element = results.Where<string>(item => item == "60").SingleOrDefault(); Assert.IsNotNull(element, "the element expected is not exits"); }