Changeset 56759 for trunk/tests/phpunit/data/themedir1/block-theme-with-hooked-blocks/blocks/hooked-after/block.json

Tests: Cover Block Hooks integration with a custom block theme

Adds a simplified version of Twenty Twenty-Three theme that helps testing Block Hooks integration. The theme contains:

• The required index.html template.
• The optional single.html template used with tests.
• 3 template parts where two of them reference patterns.
• 3 patterns referenced in the templates and the template parts.

New tests automatically register 4 custom blocks with the test theme where each of them hooks into another block using all four target relative positions: before, after, firstChild, lastChild.

The tests verify that the block gets hooked into the correct positions when targeting:

• template
• template part
• pattern

Props ockham, costdev.
See #59313, #59383.
Follow-up [56610].