src/Tests/BigPipeNoJsDetectionTest.php             | 85 +++++++++++++++++-----
 .../src/EventSubscriber/BigPipeTestSubscriber.php  |  2 +-
 2 files changed, 68 insertions(+), 19 deletions(-)

diff --git a/src/Tests/BigPipeNoJsDetectionTest.php b/src/Tests/BigPipeNoJsDetectionTest.php
index 75366d0..8a0cfb2 100644
--- a/src/Tests/BigPipeNoJsDetectionTest.php
+++ b/src/Tests/BigPipeNoJsDetectionTest.php
@@ -32,7 +32,7 @@ class BigPipeNoJsDetectionTest extends WebTestBase {
    *
    * @var array
    */
-  public static $modules = ['big_pipe'];
+  public static $modules = ['big_pipe', 'big_pipe_test'];
 
   /**
    * {@inheritdoc}
@@ -93,10 +93,6 @@ class BigPipeNoJsDetectionTest extends WebTestBase {
    * Tests BigPipe-delivered HTML responses when JavaScript is enabled.
    */
   public function testBigPipe() {
-    $this->container->get('module_installer')->install(['big_pipe_test']);
-    $this->rebuildContainer();
-    $this->rebuildAll();
-
     $this->drupalLogin($this->rootUser);
     $this->assertSessionCookieExists(TRUE);
     $this->assertBigPipeNoJsCookieExists(FALSE);
@@ -167,7 +163,7 @@ class BigPipeNoJsDetectionTest extends WebTestBase {
     ];
 
     $this->pass('Verifying BigPipe no-JS placeholders & replacements…', 'Debug');
-    $this->assertSetsEqual(array_keys($expected_big_pipe_nojs_placeholders), explode(' ', $this->drupalGetHeader('BigPipe-Test-No-Js-Placeholders')));
+    $this->assertSetsEqual(array_keys($expected_big_pipe_nojs_placeholders), array_map('rawurldecode', explode(' ', $this->drupalGetHeader('BigPipe-Test-No-Js-Placeholders'))));
     foreach ($expected_big_pipe_nojs_placeholders as $big_pipe_nojs_placeholder => $expected_replacement) {
       $this->pass('Checking whether the replacement for the BigPipe no-JS placeholder "' . $big_pipe_nojs_placeholder . '" is present:');
       $this->assertRaw($expected_replacement);
@@ -221,6 +217,63 @@ class BigPipeNoJsDetectionTest extends WebTestBase {
     $this->assertEqual($expected_stream_order, array_values($actual_stream_order));
   }
 
+  /**
+   * Tests BigPipe-delivered HTML responses when JavaScript is disabled.
+   */
+  public function testBigPipeNoJs() {
+    $this->drupalLogin($this->rootUser);
+    $this->assertSessionCookieExists(TRUE);
+    $this->assertBigPipeNoJsCookieExists(FALSE);
+
+    // By calling checkForMetaRefresh() manually here, we simulate JavaScript
+    // being disabled, because as far as the BigPipe module is concerned, it is
+    // enabled in the browser when the BigPipe no-JS cookie is set.
+    // @see setUp()
+    $this->doMetaRefresh();
+    $this->assertBigPipeNoJsCookieExists(TRUE);
+
+    $this->drupalGet(Url::fromRoute('big_pipe_test'));
+
+    // 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);
+
+    $this->pass('Verifying BigPipe response headers…', 'Debug');
+    $this->assertTrue(FALSE !== strpos($this->drupalGetHeader('Cache-Control'), 'private'), 'Cache-Control header set to "private".');
+    $this->assertEqual('no-store, content="BigPipe/1.0"', $this->drupalGetHeader('Surrogate-Control'));
+    $this->assertEqual('no', $this->drupalGetHeader('X-Accel-Buffering'));
+
+    // Keys: BigPipe no-JS placeholder markup. Values: expected replacement markup.
+    $expected_big_pipe_nojs_placeholders = [
+      'big_pipe_nojs_placeholder_attribute_safe:&lt;hello' => '<marquee>Yarhar llamas forever!</marquee>',
+      'big_pipe_nojs_placeholder_attribute_safe:form_action_cc611e1d' => '<form class="big-pipe-test-form" data-drupal-selector="big-pipe-test-form" action="' . base_path() . 'big_pipe_test"',
+      'big_pipe_nojs_placeholder_attribute_safe:e88b559cce72c80b687d56b0e2a3a5ae4b66bc0e' => $this->container->get('csrf_token')->get('admin/appearance/default'),
+      '<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>',
+      '<div data-big-pipe-nojs-placeholder-id="timecurrent-timetime"></div>' => '<time datetime=1991-03-14"></time>',
+    ];
+
+    $this->pass('Verifying BigPipe no-JS placeholders & replacements…', 'Debug');
+    $this->assertSetsEqual(array_keys($expected_big_pipe_nojs_placeholders), array_map('rawurldecode', explode(' ', $this->drupalGetHeader('BigPipe-Test-No-Js-Placeholders'))));
+    foreach ($expected_big_pipe_nojs_placeholders as $big_pipe_nojs_placeholder => $expected_replacement) {
+      $this->pass('Checking whether the replacement for the BigPipe no-JS placeholder "' . $big_pipe_nojs_placeholder . '" is present:');
+      $this->assertRaw($expected_replacement);
+    }
+
+    $this->pass('Verifying BigPipe placeholders & replacements…', 'Debug');
+    $this->assertEqual('<none>', $this->drupalGetHeader('BigPipe-Test-Placeholders'));
+
+    $this->pass('Verifying BigPipe assets are absent…', 'Debug');
+    $this->assertFalse(empty($this->getDrupalSettings()), 'drupalSettings and BigPipe asset library absent.');
+
+    $this->pass('Verifying BigPipe start/stop signals are absent…', 'Debug');
+    $this->assertNoRaw(static::START_SIGNAL, 'BigPipe start signal absent.');
+    $this->assertNoRaw(static::STOP_SIGNAL, 'BigPipe stop signal absent.');
+  }
+
+  /**
+   * Asserts whether arrays A and B are equal, when treated as sets.
+   */
   protected function assertSetsEqual(array $a, array $b) {
     $a_set = $a;
     sort($a_set);
@@ -230,16 +283,6 @@ class BigPipeNoJsDetectionTest extends WebTestBase {
   }
 
   /**
-   * Tests BigPipe-delivered HTML responses when JavaScript is disabled.
-   */
-  public function atestBigPipeNoJs() {
-    // BigPipe asset library: absent.
-    $this->assertFalse(empty($this->getDrupalSettings()), 'drupalSettings present.');
-    $this->assertFalse(in_array('big_pipe/big_pipe', explode(',', $this->getDrupalSettings()['ajaxPageState']['libraries'])), 'BigPipe asset library is absent.');
-
-  }
-
-  /**
    * Asserts whether a BigPipe no-JS cookie exists or not.
    */
   protected function assertBigPipeNoJsCookieExists($expected) {
@@ -267,8 +310,7 @@ class BigPipeNoJsDetectionTest extends WebTestBase {
   protected function assertBigPipeNoJsMetaRefreshRedirect() {
     // Let the browser check for a meta refresh.
     $original_url = $this->url;
-    $this->maximumMetaRefreshCount++;
-    $this->checkForMetaRefresh();
+    $this->doMetaRefresh();
 
     $this->assertEqual($original_url, $this->url, 'Redirected back to the original location.');
 
@@ -290,4 +332,11 @@ class BigPipeNoJsDetectionTest extends WebTestBase {
     $this->assertNoRaw('<noscript><meta http-equiv="Refresh" content="0; URL=', 'Once the BigPipe no-JS cookie is set, the <meta> refresh is absent: only one redirect ever happens.');
   }
 
+  protected function doMetaRefresh() {
+    $this->maximumMetaRefreshCount = 1;
+    $this->checkForMetaRefresh();
+    $this->maximumMetaRefreshCount = 0;
+    $this->metaRefreshCount = 0;
+  }
+
 }
diff --git a/tests/modules/big_pipe_test/src/EventSubscriber/BigPipeTestSubscriber.php b/tests/modules/big_pipe_test/src/EventSubscriber/BigPipeTestSubscriber.php
index 78b4599..6af1028 100644
--- a/tests/modules/big_pipe_test/src/EventSubscriber/BigPipeTestSubscriber.php
+++ b/tests/modules/big_pipe_test/src/EventSubscriber/BigPipeTestSubscriber.php
@@ -36,7 +36,7 @@ class BigPipeTestSubscriber implements EventSubscriberInterface {
     }
 
     if (!empty($attachments['big_pipe_nojs_placeholders'])) {
-      $response->headers->set('BigPipe-Test-No-Js-Placeholders', implode(' ', array_keys($attachments['big_pipe_nojs_placeholders'])));
+      $response->headers->set('BigPipe-Test-No-Js-Placeholders', implode(' ', array_map('rawurlencode', array_keys($attachments['big_pipe_nojs_placeholders']))));
     }
   }