public void contains_one_element_returns_true_when_passing_enumerable_with_one_item()
        {
            var oneItemArray = new[] { 1 };

            Assert.True(oneItemArray.ContainsOneElement());
        }
        public void contains_one_element_returns_false_when_passing_enumerable_with_two_items()
        {
            var twoItemsArray = new[] {1, 2};

            Assert.False(twoItemsArray.ContainsOneElement());
        }