Comment Template Block: Add test coverage for context setting

[ockham]

What?

Add a unit test to verify that the Comment Template block sets commentId context as expected. Follow up to #50279; see #50279 (comment) for context.

Why?

Conversation on #50279 indicates that it's fairly easy to make a change to the relevant code which would break this behavior. Consequently, it makes sense to guard against such breakage.

How?

By inserting a block which requires commentId context to work via the render_block hook.

Testing Instructions

1. Verify that test pass. Locally, this can be done via npm run test:unit:php -- --group=blocks.
2. Now revert 4409ba4 and rebuild blocks (npm run build). Re-run the test, and verify that it fails now.

Note

In the long run, this test should be merged into wordpress-develop's renderCommentTemplate.php test file.

[github-actions]

Flaky tests detected in e4c1ff7.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/5058441320
📝 Reported issues:

• [Flaky Test] should allow to return Global Styles root when example is clicked #50799 in /test/e2e/specs/site-editor/style-book.spec.js
• [Flaky Test] should disable toolbar buttons when open #50837 in /test/e2e/specs/site-editor/style-book.spec.js
• [Flaky Test] should have tabs containing block examples #50838 in /test/e2e/specs/site-editor/style-book.spec.js
• [Flaky Test] should open correct Global Styles panel when example is clicked #50839 in /test/e2e/specs/site-editor/style-book.spec.js

[ockham]

In the long run, this test should be merged into wordpress-develop's renderCommentTemplate.php test file.

PR: WordPress/wordpress-develop#4507

[gziolo]

Thank you for adding this test covering special case for the Comment Template block. It was very helpful to see the PR targeting WordPress Core to confrim that setup code is only duplicated to run it in the Gutenberg repo.

Have you considered adding an additional assertion to verify whether the $comment_author_name_block variable is non-empty string or has some shape at all. It would cover the case when the block would stop rendering any output, but it might be covered with other tests. So it isn't a blocker, but something for you to decide.

[ockham]

Have you considered adding an additional assertion to verify whether the $comment_author_name_block variable is non-empty string or has some shape at all. It would cover the case when the block would stop rendering any output, but it might be covered with other tests. So it isn't a blocker, but something for you to decide.

Ah yeah, sounds like a great idea! I'll add something.