public void RemoveDuplicateSmallLetterStrings()
        {
            var strings = SampleStringsStub.DuplicateSmallLetterStrings();

            var result = StringFilter.SmallLettersStrings(strings);

            Assert.IsTrue(result.Count == 2);
            Assert.AreEqual("al", result.ElementAt(0));
            Assert.AreEqual("bar", result.ElementAt(1));
        }