BigPipe response delivery test coverage with JS enabled & disabled (BigPipe + HtmlResponseBigPipeSubscriber)

Here is a first iteration. This tests 2 out of the 5 types of placeholders I want to test. And it only tests the "JS on" case, not the "JS off" case yet.

But the bulk of the test infrastructure is here, I should be able to finish this swiftly tomorrow morning.

I'll continue working on this tomorrow morning.

Fixed those failures. Both due to expectations assuming Drupal is installed in a subdirectory.

At the same time got rid of all that hardcoded JSON. Instead keeping more legible data structures in PHP that are converted to JSON when testing.

Addressed

// @todo verify positions of $placeholder_replacement_positions, $start_signal_position, $stop_signal_position

Also improved test debug output, which should help a lot in making these tests and their results easier to understand & maintain.

One less @todo:

      // 3. HTML attribute value subset placeholder: CSRF token in link.
-    // @todo

90% of the time to get this one working was spent on this beauty:

    // Ensure we can generate CSRF tokens for the current user's session.
    $session_data = $this->container->get('session_handler.write_safe')->read($this->cookies[$this->getSessionName()]['value']);
    $csrf_token_seed = unserialize(explode('_sf2_meta|', $session_data)[1])['s'];
    $this->container->get('session_manager.metadata_bag')->setCsrfTokenSeed($csrf_token_seed);

Oh, Symfony…

And another @todo gone:

     // 4. Edge case: custom string to be considered as a placeholder that
     // happens to not be valid HTML.
-    // @todo

This one was painless (and glorious, check out the markup it generates!)

And here's then the corresponding BigPipe no-JS test.

+++ b/src/Tests/BigPipeNoJsDetectionTest.php
@@ -221,6 +217,63 @@ class BigPipeNoJsDetectionTest extends WebTestBase {
+      '<div data-big-pipe-nojs-placeholder-id="callback=Drupal%5CCore%5CRender%5CElement%5CStatusMessages%3A%3ArenderMessages&amp;args[0]&amp;token=a8c34b5e"></div>' => '<marquee>Yarhar llamas forever!</marquee>',

I defined the wrong expectation here. That's not the status message markup.

The actual expected markup (patch attached) would also verify the additional CSS that gets loaded, which means when JS is off's second point in the IS is then also verified.

First round of clean-up:

• rename BigPipeNoJsDetectionTest to BigPipeTest
• fix & improve test docblocks

Update big_pipe_test.module so that \Drupal\big_pipe\Tests\BigPipeTest::testNoJsDetection() no longer needs to install the session_exists_cache_context_test module.

Improve docs/helper function name for the special <meta> refresh handling.

This was already using the same five test cases as the unit tests were. This reroll makes that more maintainable by centralizing all aspects of all five test cases in a single class, that then both the unit test and the integration tests can call out to.

Final clean-up. The test logic of \Drupal\big_pipe\Tests\BigPipeTest::testBigPipe() and \Drupal\big_pipe\Tests\BigPipeTest::testBigPipeNoJs() is now much easier to follow, and should be clear on at least a high level to all readers.

lgtm