Tests in https://github.com/rust-lang/rust can be linked to rules in the Reference. The rule will include a link to the tests, and there is also an appendix that tracks how the rules are currently linked.
Tests in the tests directory can be annotated with the //@ reference: x.y.z header to link them to a rule. The header can be specified multiple times if a single file covers multiple rules.
Compiler developers are not expected to add reference annotations to tests. However, if they do want to help, their cooperation is very welcome. Reference authors and editors are responsible for ensuring every rule has a test associated with it.
The tests are beneficial for reviewers to see the behavior of a rule. They are also a benefit to readers who may want to see examples of particular behaviors. When adding new rules, you should wait until the Reference side is approved before submitting a PR to rust-lang/rust (to avoid churn if we decide on different names).
Prefixed rule names should not be used in tests. That is, do not use something like asm.rules when there are specific rules like asm.rules.reg-not-input.
We do not expect 100% coverage at any time. Although it would be nice, it is unrealistic due to the sequence in which things are developed and the resources available.