Bug

• package version: 1.1.3
• node version: 16.16.0
• npm (or yarn) version: npm 8.11.0

What I tried initially

Initially the only things I did before using messages in expect were

1. npm install --save-dev jest-expect-message
2. Add import "jest-expect-message"; to jest-setup.ts.

This worked initially but after change the test and running the test again, I started getting:

> @dfinity/[email protected] test
> TZ=UTC jest "feature-flags.store.spec.ts"

 FAIL  src/tests/lib/stores/feature-flags.store.spec.ts
  ● Test suite failed to run

    src/tests/lib/stores/feature-flags.store.spec.ts:24:9 - error TS2554: Expected 1 arguments, but got 2.

    24         `FeatureFlag ${feature} should be exported from feature-flags.store.ts`
               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Test Suites: 1 failed, 1 total
Tests:       0 total
Snapshots:   0 total
Time:        2.076 s
Ran all test suites matching /feature-flags.store.spec.ts/i.

What didn't work

I tried of all the following but the issue remained:

1. Add "jest-expect-message", to setupFilesAfterEnv: in jest.config.cjs.
2. Add "files": ["node_modules/jest-expect-message/types/index.d.ts"], to tsconfig.json
3. Add "jest/valid-expect": "off", in rules: in .eslintrc.cjs.

What worked

1. After running jest --clearCache the issue would go away, but return after making some changes and running the test again.
2. npm install --save-dev @types/jest-expect-message made the issue go away consistently. However, the package is deprecated and when I look inside the package it looks basically empty. So I don't understand how this can have an effect.
3. Using import "jest-expect-message"; in the test file itself rather than in jest-setup.ts works. Is this the intended way to use it?

Any insight into what might be going on would be greatly appreciated.

If you want, you can see our entire setup at https://github.com/dfinity/nns-dapp/compare/main...kloet/jem3

I had some luck by adding the package to my tsconfig types.

{
  "compilerOptions": {
    "types": ["jest", "jest-expect-message"]
  }
}

There is an alternative to explicitly declared "types". You can declare jest-expect-message as an @types/* package in package.json:

{
  "devDependencies": {
    "@types/jest-expect-message": "npm:jest-expect-message@*",
  }
}

Run yarn install after adding the line. All will work as if you have @types/jest-expect-message installed, but the typings will come from jest-expect-message package.

The suggestion from @mrazauskas worked for me. I was also able to remove the files key from tsconfig.json. Maybe a documentation update is in order?