https://docs.rs/goldentests/0.3.7/goldentests/
Why golden tests?
Golden tests allow you to specify the output of some command within a file and automatically ensure that that output doesn't change. If it does, goldentests will show an error-diff showing the expected and actual output. This way, whenever the output of something changes a human can see the change and decide if it should be kept or is a bug and should be reverted.
What are golden tests useful for?
Golden tests are especially useful for applications that take a file as input and produce output of some kind. For example: compilers and config-parsers (well, parsers in general) are two such applications that can benefit form automated golden tests. In the case of a config parser, you would be able to provide many config examples as tests and ensure that your parser was able to read the files with the expected stdout/stderr output and exit code.
https://docs.rs/goldentests/0.3.7/goldentests/