When fixture value `R` is a function, TypeScript sometimes confuses
function `R` and function `async ({}, use) => {}`. This leads to
`any` types in the latter because it could be either of the functions
as TS thinks.
The solution is to only accept the second syntax, assuming that noone
passes fixture value that is a function as is:
```js
// This will stop working.
test.extend<{ foo: (x: number) => number }>({
foo: x => 2 * x,
});
// This will get inferred types and autocomplete.
test.extend<{ foo: (x: number) => number }>({
foo: async ({}, use) => {
await use(x => 2 * x);
},
});
```
Each hook gets its own test scope. This is not too useful for
object fixtures like `page` (although one can use a page in
`beforeAll` to save storage state), but much more useful for option
fixtures like `viewport`.
- Source now lives at `src/test`.
- Former folio tests live at `tests/playwright-test`.
- We use `src/test/internal.ts` that exposes base test without
Playwright fixtures for most tests (to avoid modifications for now).
- Test types live in `types/testFoo.d.ts`.
- Stable test runner is installed to `tests/config/test-runner` during `npm install`.
- All deps including test-only are now listed in `package.json`.
Non-test deps must also be listed in `build_package.js` to get included.
