private void TestAnnotation(SyntaxAnnotation annotation, SyntaxNode root, SyntaxTrivia oldTrivia)
{
var results = root.GetAnnotatedTrivia(annotation);
Assert.Equal(1, results.Count());
var annotatedTrivia = results.Single();
// try to check whether it is same token as old token.
Assert.Equal(oldTrivia.FullSpan, annotatedTrivia.FullSpan);
Assert.Equal(oldTrivia.Span, annotatedTrivia.Span);
Assert.True(oldTrivia.IsEquivalentTo(annotatedTrivia));
}