public void ReplaceTest() { var newText1 = text.Replace('i', '1'); Assert.AreEqual(newText1.Text, text.Text.Replace('i', '1')); Assert.AreEqual(newText1.AnySpanReferenceEquals(text), false); var newText2 = text.Replace("t", "tt"); var newText3 = text.Replace("1", (string)null); var newText4 = text.Replace("t", (string)null); Assert.AreEqual(newText2.Text, text.Text.Replace("t", "tt")); Assert.AreEqual(newText2.AnySpanReferenceEquals(text), false); Assert.AreEqual(newText3.Text, text.Text); Assert.AreEqual(newText3.AnySpanReferenceEquals(text), false); Assert.AreEqual(newText4.Text, text.Text.Replace("t", null)); Assert.AreEqual(newText4.AnySpanReferenceEquals(text), false); }