diff --git a/core/modules/media/tests/src/FunctionalJavascript/MediaSourceTestBase.php b/core/modules/media/tests/src/FunctionalJavascript/MediaSourceTestBase.php
index c6ea4ec7dbad3a0d2bc22982fde9c487646e2540..ce0f185ecb3f72bcc524acd21747943910472cf1 100644
--- a/core/modules/media/tests/src/FunctionalJavascript/MediaSourceTestBase.php
+++ b/core/modules/media/tests/src/FunctionalJavascript/MediaSourceTestBase.php
@@ -123,7 +123,6 @@ public function doTestCreateMediaType($media_type_id, $source_id, array $provide
 
     // Save the form to create the type.
     $page->pressButton('Save');
-    $assert_session->statusCodeEquals(200);
     $assert_session->pageTextContains('The media type ' . $media_type_id . ' has been added.');
     $this->drupalGet('admin/structure/media');
     $assert_session->pageTextContains($media_type_id);
diff --git a/core/modules/media/tests/src/FunctionalJavascript/MediaUiJavascriptTest.php b/core/modules/media/tests/src/FunctionalJavascript/MediaUiJavascriptTest.php
index 38a6227440aae5ce65aaf8573b4a27e324a11dd0..981da61d59abe21dcc6c71776fdb5adc48d265d2 100644
--- a/core/modules/media/tests/src/FunctionalJavascript/MediaUiJavascriptTest.php
+++ b/core/modules/media/tests/src/FunctionalJavascript/MediaUiJavascriptTest.php
@@ -54,7 +54,6 @@ public function testMediaTypes() {
     $assert_session = $this->assertSession();
 
     $this->drupalGet('admin/structure/media');
-    $assert_session->statusCodeEquals(200);
     $assert_session->pageTextContains('No media types available. Add media type.');
     $assert_session->linkExists('Add media type');
 
@@ -69,10 +68,8 @@ public function testMediaTypes() {
     $this->assertJsCondition("jQuery('.form-item-source-configuration-test-config-value').length > 0;");
     $page->fillField('description', $description);
     $page->pressButton('Save');
-    $assert_session->statusCodeEquals(200);
     $assert_session->pageTextContains('The media type ' . $name . ' has been added.');
     $this->drupalGet('admin/structure/media');
-    $assert_session->statusCodeEquals(200);
     $assert_session->pageTextContains($name);
     $assert_session->pageTextContains($description);
 
@@ -142,7 +139,7 @@ public function testMediaTypes() {
     $page->uncheckField('options[status]');
     $page->checkField('options[queue_thumbnail_downloads]');
     $page->pressButton('Save');
-    $assert_session->statusCodeEquals(200);
+    $assert_session->pageTextContains("The media type $new_name has been updated.");
 
     // Test if edit worked and if new field values have been saved as expected.
     $this->drupalGet('admin/structure/media/manage/' . $this->testMediaType->id());
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/Core/Session/SessionTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Core/Session/SessionTest.php
index e02e0dfb0f02afe47c26f8cf1c6386692fd941e3..fa2d541c8a8b18f1e0ce24865a3198c4632f48eb 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/Core/Session/SessionTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Core/Session/SessionTest.php
@@ -48,13 +48,10 @@ public function testSessionExpiration() {
     // number of times.
     $this->drupalGet('<front>');
 
-    $session_assert = $this->assertSession();
-
     $page = $this->getSession()->getPage();
 
     for ($i = 0; $i < 25; $i++) {
       $page->clickLink('Link to front page');
-      $session_assert->statusCodeEquals(200);
     }
   }
 
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/JavascriptTestBase.php b/core/tests/Drupal/FunctionalJavascriptTests/JavascriptTestBase.php
index d5156eeb5cb6d469b59478f846b3a5644111df23..8aa46c7ec1a3a47c82b5634cbe9ad0ef9c6aea36 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/JavascriptTestBase.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/JavascriptTestBase.php
@@ -7,7 +7,7 @@
 use Zumba\Mink\Driver\PhantomJSDriver;
 
 /**
- * Runs a browser test using PhantomJS.
+ * Runs a browser test using a driver that supports Javascript.
  *
  * Base class for testing browser interaction implemented in JavaScript.
  */
@@ -142,7 +142,7 @@ protected function createScreenshot($filename, $set_background_color = TRUE) {
    * {@inheritdoc}
    */
   public function assertSession($name = NULL) {
-    return new JSWebAssert($this->getSession($name), $this->baseUrl);
+    return new WebDriverWebAssert($this->getSession($name), $this->baseUrl);
   }
 
   /**
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/LegacyJavascriptTestBase.php b/core/tests/Drupal/FunctionalJavascriptTests/LegacyJavascriptTestBase.php
new file mode 100644
index 0000000000000000000000000000000000000000..7cef5b8c6c37436e8c66bf2d981765bd7779bc43
--- /dev/null
+++ b/core/tests/Drupal/FunctionalJavascriptTests/LegacyJavascriptTestBase.php
@@ -0,0 +1,20 @@
+<?php
+
+namespace Drupal\FunctionalJavascriptTests;
+
+/**
+ * Runs a browser test using PhantomJS.
+ *
+ * Base class for testing browser interaction implemented in JavaScript.
+ */
+abstract class LegacyJavascriptTestBase extends JavascriptTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function assertSession($name = NULL) {
+    // Return a WebAssert that supports status code and header assertions.
+    return new JSWebAssert($this->getSession($name), $this->baseUrl);
+  }
+
+}
diff --git a/core/tests/Drupal/FunctionalJavascriptTests/WebDriverWebAssert.php b/core/tests/Drupal/FunctionalJavascriptTests/WebDriverWebAssert.php
new file mode 100644
index 0000000000000000000000000000000000000000..16b1281d4d8be0062bae40374e1683ad4043a07b
--- /dev/null
+++ b/core/tests/Drupal/FunctionalJavascriptTests/WebDriverWebAssert.php
@@ -0,0 +1,58 @@
+<?php
+
+namespace Drupal\FunctionalJavascriptTests;
+
+/**
+ * Defines a JSWebAssert with no support for status code and header assertions.
+ */
+class WebDriverWebAssert extends JSWebAssert {
+
+  /**
+   * The use of statusCodeEquals() is not available.
+   *
+   * @param int $code
+   *   The status code.
+   */
+  public function statusCodeEquals($code) {
+    @trigger_error('Support for statusCodeEquals is to be dropped from Javascript tests. See https://www.drupal.org/node/2857562.');
+    parent::statusCodeEquals($code);
+  }
+
+  /**
+   * The use of statusCodeNotEquals() is not available.
+   *
+   * @param int $code
+   *   The status code.
+   */
+  public function statusCodeNotEquals($code) {
+    @trigger_error('Support for statusCodeNotEquals is to be dropped from Javascript tests. See https://www.drupal.org/node/2857562.');
+    parent::statusCodeNotEquals($code);
+  }
+
+  /**
+   * The use of responseHeaderEquals() is not available.
+   *
+   * @param string $name
+   *   The name of the header.
+   * @param string $value
+   *   The value to check the header against.
+   */
+  public function responseHeaderEquals($name, $value) {
+    @trigger_error('Support for responseHeaderEquals is to be dropped from Javascript tests. See https://www.drupal.org/node/2857562.');
+    parent::responseHeaderEquals($name, $value);
+  }
+
+  /**
+   * The use of responseHeaderNotEquals() is not available.
+   *
+   * @param string $name
+   *   The name of the header.
+   * @param string $value
+   *   The value to check the header against.
+   */
+  public function responseHeaderNotEquals($name, $value) {
+    @trigger_error('Support for responseHeaderNotEquals is to be dropped from Javascript tests. See https://www.drupal.org/node/2857562.');
+    parent::responseHeaderNotEquals($name, $value);
+  }
+
+}
diff --git a/core/tests/Drupal/Tests/BrowserTestBase.php b/core/tests/Drupal/Tests/BrowserTestBase.php
index bd50c23b4863377be482db8cb76b9c602f5bd009..8ad783a8ab49aa4e36d7e7edb89d856153072322 100644
--- a/core/tests/Drupal/Tests/BrowserTestBase.php
+++ b/core/tests/Drupal/Tests/BrowserTestBase.php
@@ -736,7 +736,6 @@ protected function drupalLogin(AccountInterface $account) {
     }
 
     $this->drupalGet('user/login');
-    $this->assertSession()->statusCodeEquals(200);
     $this->submitForm([
       'name' => $account->getUsername(),
       'pass' => $account->passRaw,
@@ -761,7 +760,6 @@ protected function drupalLogout() {
     // screen.
     $assert_session = $this->assertSession();
     $this->drupalGet('user/logout', ['query' => ['destination' => 'user']]);
-    $assert_session->statusCodeEquals(200);
     $assert_session->fieldExists('name');
     $assert_session->fieldExists('pass');