As most of our testing cases have to do with Rust compilation our tests have to be conducted at build time.
To be able to test those cases, a dedicated Rust crate is used, trybuild.
trybuild is a crate that will first try to compile the files in the test folder and then generate files compiling all outputs on stderr. Those files will later on serve as references and all later tests will verify that all stderr messages outputs are the same as the references.
When running some new tests for the first time a wip folder is generated in the crates/macro folder. It contains the
new references. Those references should be moved to their respective test folder to ensure future tests to be correct.