Custom matchers with auto definition types

For some custom needs, special matcher are needed. expect from jest provides an extend method for doing that. Jasmine is also able to do it.

There is something common between both solutions which Vitest can improve: generate the type definition automatically.

So being able to add our custom matchers, and then, get automatically the type globally either by a definition type file put in the source code or by a type put in cache somewhere in node_modules of Vitest which would be taken in order by typescript on test files.

[antfu]

Yeah, I think it’s better to manage the extra types yourself (it’s not that long anyway). Automation on this could potentially be a footgun.

I think we might need to document which module and interface to extend. @sheremet-va do you mind checking how it would work on the user lang and maybe sending a PR to docs? Thanks

[sheremet-va]

I think developers should do it themselves. The best we can do is provide documentation. Hope we can close the issue.