public void ReplaceSpanTest()
{
Span span = new Span()
{
Text = "This is text."
};
FormattedString newText = text.ReplaceSpan(span, new Span());
Assert.AreEqual(newText.Length, text.Length);
Assert.AreEqual(newText.Text, text.Text.Replace(span.Text, null));
Assert.AreEqual(newText.AnySpanReferenceEquals(text), false);
}