Loading Functional Tests: Replace `assert` with `expect` by seanpdoyle · Pull Request #1466

Loading Functional Tests: Replace `assert` with `expect` by seanpdoyle · Pull Request #1466 · hotwired/turbo

Follow-up to hotwired#1454

This commit continues to migrate from `assert` usage toward Playwright's
`expect`. This commit focuses on the
`src/tests/functional/loading_tests.js` file.

The majority of this diff replaces `hasSelector` with
`expect(…).toBeAttached()` and `expect(…).toHaveAttribute()`.

[assertions]: https://playwright.dev/docs/test-assertions