[Feature] Add possibility to run only one test from several parameterized tests

[viraxslot]

Hi team. It's a proposal for Playwright Test Runner.

I really like parameterized tests, they allow to decrease amount of code:
https://playwright.dev/docs/test-parameterize#parameterized-tests

What I don't like in them: debugging.
Because I need:

1. Set "only" for the test function.
2. Comment a part of test data array (sometimes it can be really huge, so scroll up, scroll down).
3. Run the test, debug, fix the problem.
4. Uncomment test data and remove "only".

Feature request: it would be really nice to have something like test.first and test.last functions to easily debug parameterized tests.
test.first runs the first test only (takes the first element from test data array).
test.last runs the last only.

So it could look like:

const testData = [1, 2, 3, 4, 5];

// should pass
testData.forEach(data => {
  test.first('check array value 1', () => {
    expect(data).toBe(1);
  });
});

// should fail
testData.forEach(data => {
  test.last('check array value 2', () => {
    expect(data).toBe(1);
  });
});

I hope it's possible to implement and you'll like the idea :)

[viraxslot]

I'm curious why I commented code all this time because I can do testData.slice(0,1), but I'll keep the request as is.
Maybe you have an another workaround :)

[dgozman]

I'm curious why I commented code all this time because I can do testData.slice(0,1), but I'll keep the request as is. Maybe you have an another workaround :)

I was about to suggest testData.slice(0, 1), but then read your comment 😄

I don't have a better idea for the forEach style. If we ever implement test.each or similar, we should make sure it's easy to debug as you say.

[viraxslot]

@dgozman yeah, it was an interesting found 😁 I just used to use this approach, and did it out of habit. Thanks for linking the issue.

[dgozman]

Closing this in favor of #7036.