public void TestToLower()
        {
            const string firstString = "Hello World";

            var textCleaner = new TextCleaner(firstString);

            Assert.AreEqual(textCleaner.ToLower().ToString(), firstString.ToLower());

            Assert.AreEqual(new TextCleaner("").ToLower().ToString(), "");
            Assert.AreEqual(new TextCleaner("hello").ToLower().ToString(), "hello");
        }