Add @cover annotation in test-load file and add support for codecov

[sarthak-19]

Summary

This PR adds @cover annotation for test cases and add .yml file that can be used to configure codecov for automated test coverage in github actions.

Addresses #1284

Relevant technical choices

I've addressed the following file plugins/webp-uploads/tests/test-load.php for adding @cover annotation, if the approach is approved will extend this to other files.

[swissspidy]

@sarthak-19 Welcome, and thanks for opening this! I just stumbled upon the PR and left a couple of comments for things that caught my eye.

[sarthak-19]

@sarthak-19 Welcome, and thanks for opening this! I just stumbled upon the PR and left a couple of comments for things that caught my eye.

@swissspidy Thank you so much for the feedback. I've addressed those and looking forward to keep improving 😄

[westonruter]

Since collecting code coverage takes much longer, as I recall, should the coverage only happen for one of the jobs instead of for all of them?

[sarthak-19]

Yes you're right, collecting code coverage takes time, but I'm not quite sure that for which job it'll be ideal to run.
Should I run for PHP v8.0 and if this is a viable option, then will the below implementation work since we are using the latest WP version anyways?

      - name: Running single site unit tests with coverage
        if: matrix.php == '8.0'
        run: npm run test-php -- --coverage-clover=coverage.xml
      - name: Running multisite unit tests with coverage
        if: matrix.php == '8.0'
        run: npm run test-php-multisite -- --coverage-clover=coverage-multisite.xml

      - name: Upload single site coverage reports to Codecov
        if: matrix.php == '8.0'
        uses: codecov/codecov-action@v4
        with:
          token: ${{ secrets.CODECOV_TOKEN }}
          files: coverage.xml
          flags: unittests
          name: ${{ matrix.php }}-single-site-coverage
      - name: Upload multisite coverage reports to Codecov
        if: matrix.php == '8.0'
        uses: codecov/codecov-action@v2
        with:
          token: ${{ secrets.CODECOV_TOKEN }}
          files: coverage-multisite.xml
          flags: multisite
          name: ${{ matrix.php }}-multisite-coverage

cc : @westonruter

[westonruter]

You may want to refer to what was done for the AMP plugin: https://github.com/ampproject/amp-wp/blob/60a655cdad9e3431b47b2dcc3b2e5ddb86ac5c5e/.github/workflows/build-test-measure.yml#L261-L337

Note the new coverage matrix variable which is only set to true for one configuration. This would be better than having to test against a specific PHP version everywhere. Yes, I think running coverage on the most recent PHP version would be best as it should complete the fastest. So maybe do it in PHP 8.2?

cc @thelovekesh

[pbearne]

I am really glad to see I have been try to get into core ten+ years