Testing your documentation

Out-of-date documentation and examples that aren't working as promised are an unfortunate truth of many technologies. However, these examples can be valuable (black box) regression tests to make sure that we didn't break anything while improving the code, so how can they be used as such? Rust's documentation strings (///) can include executable code snippets—and they can be seen all over the place on https://www.rust-lang.org/learn!