Changing to _test definitely works. Initially I thought it wouldn’t work with Bun Test runner, but turns out there must be a typo in their error message that said the file name had to have “test” in the filename, but I checked the documentation and it says the test runner looks for “_test” and not “test”.
So I guess the options are “_test” without the namespace option or “.test” with namespace set to true in rescript.json.