[dc-programmer]

I’ve shipped unit tests that would fail but don’t run by copying the function signature of the previous test then forgetting to change the name of the new one. Only one of the tests will run (the first?).

Maybe unit tests need unit tests? (There’s probably a lint rule to catch what I describe above)

[jka]

> Maybe unit tests need unit tests? (There’s probably a lint rule to catch what I describe above)

Yep - meta-testing (ensuring that every unit test that exists in a project adds unique coverage, remains valid, runs as expected, and I'm sure many other properties) could (and should!) definitely be automated.

Some more advanced meta-testing could involve tracking changes to a project's source history over time (in other words: tests that run with commit history). By that I'm thinking of situations like: "does this test genuinely still test what it used to, after the test and/or application code was modified?"

[rcxdude]

mutation testing is one example: if you make random changes (random in terms of transforming valid code to different valid code) to the code being tested, you should expect that the test will then fail. If not, there is some part of the code's behaviour which is not being tested.

[dc-programmer]

Wow, that sounds like the future of testing. It’d be a hard to sell to manager now though. Some of those checks seem like they could be auto-generated though

[pure_simplicity]

The second one will run, because as the file gets executed top down, the second declaration overwrites the first declaration, just like when you reassign a variable.

But yeah that would be a good thing for a linter to catch. I'm not aware if any do.