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"); }