syntax_data: {"ast_node_type":"other","tokens":[{"end":69,"kind":"keyword","start":0,"text":"assert_eq!(&sm.span_to_snippet(span).unwrap(),"}]}
source_snippet:     assert_eq!(&sm.span_to_snippet(span).unwrap(), "BB\nCCC\nDDDDD");
context_before:     // Check that we are extracting the text we thought we were extracting.