Build/Test Tools: Use strict assertions in the interactivity-api tests.

[haritpanchal]

What

Reviewed the 2 files claimed on the ticket under tests/phpunit/tests/interactivity-api/.
All 33 assertEquals() calls convert to assertSame().

• wpInteractivityAPIDirectivesProcessor.php (32 assertions) — every call compared a
  string literal against $p, the WP_Interactivity_API_Directives_Processor
  instance itself, not a string. This only ever worked because PHPUnit falls
  back to __toString() when comparing a string to an object that defines
  one — assertSame() would fail on every single one of these (string !== object) if the method name were swapped without also fixing the argument.
  __toString() delegates to get_updated_html(): string
  (WP_HTML_Tag_Processor, which this class extends), the same strict
  return-type contract used in the block-bindings/ conversions from this
  ticket, so each call now explicitly asserts against
  $p->get_updated_html().
• wpInteractivityAPI.php (1 assertion) — parse_directive_name() declares
  @phpstan-return array{..., suffix: non-empty-string|null, unique_id: non-empty-string|null} and casts every non-null branch with (string), so
  the type is a documented guarantee, not an inference. The two sibling
  assertions immediately above this one in the same test already use
  assertSame() for the same structure, so this was an inconsistency fix.

Testing

npm run test:php -- --group interactivity-api
381 tests, 999 assertions, 0 failures

node ./tools/local-env/scripts/docker.js run --rm php ./vendor/bin/phpunit -c tests/phpunit/multisite.xml --group interactivity-api
381 tests, 999 assertions, 0 failures

PHPCS clean on both changed files. Test-only change; no production code touched.

Trac ticket: https://core.trac.wordpress.org/ticket/64895

Use of AI Tools

AI assistance: Yes
Tool(s): Claude Code
Model(s): Claude Opus 5
Used for: Helping locate candidate files and cross-check each expected literal
against the return-type contract. I reviewed the conversions and take
responsibility for the final code.

[github-actions]

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Props haritpanchal.

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[lancewillett]

https://core.trac.wordpress.org/changeset/63622