JsWebAssert::assertWaitOnAjaxRequest() should use Behat\Mink\Exception\ExpectationException not RuntimeException

Problem/Motivation

When assertWaitOnAjaxRequest() fails, it uses \RuntimeException which immediately halts the test and bypasses things like tearDown().

Discovered at #3218985-20: CKEditor 5 admin UI's AJAX logic and form alterations are too complex and brittle and #3218985-21: CKEditor 5 admin UI's AJAX logic and form alterations are too complex and brittle:

What's weird is that \Drupal\Tests\ckeditor5\FunctionalJavascript\CKEditor5TestBase::tearDown() which was added in #3228355: PHP warning when saving text format with CKE5: $form_state->getTriggeringElement() unexpectedly returning NULL should be causing this to be visible, but it's … just not. It seems that the tearDown() is perhaps not being called in the case of Functional JS tests failing early? Yet ::tearDown() is supposed to be called always… I could decorate $assert_session->assertWaitOnAjaxRequest(); in CKE5 tests just so we get better error response checking… using the same technique as I added in \Drupal\Tests\media\FunctionalJavascript\CKEditorIntegrationTest::getLastPreviewRequestTransferSize().

+

Actually … I think I figured out why:

00:06:37.487 FATAL Drupal\Tests\ckeditor5\FunctionalJavascript\CKEditor5Test: test runner returned a non-zero error code (2).

This is because \Drupal\FunctionalJavascriptTests\JSWebAssert::assertWaitOnAjaxRequest() triggers a \RuntimeException that the test runner won't handle. So it instantly aborts the test, without running ::tearDown()!

While the plan is to remove assertWaitOnAjaxRequest, in the meantime this fix will stop preventing issues like #3228956: PHP notices are not detected for headless browser-triggered requests in FunctionalJavascript tests from progressing.

Steps to reproduce

TBD

Proposed resolution

Replace \RuntimeException with Behat\Mink\Exception\ExpectationException

Remaining tasks

Write tests

User interface changes

N/A

API changes

N/A

Data model changes

N/A

Release notes snippet

N/A