diff --git a/core/modules/color/src/Tests/ColorConfigSchemaTest.php b/core/modules/color/test/src/Functional/ColorConfigSchemaTest.php
similarity index 87%
rename from core/modules/color/src/Tests/ColorConfigSchemaTest.php
rename to core/modules/color/test/src/Functional/ColorConfigSchemaTest.php
index 941e520..157deb8 100644
--- a/core/modules/color/src/Tests/ColorConfigSchemaTest.php
+++ b/core/modules/color/test/src/Functional/ColorConfigSchemaTest.php
@@ -1,15 +1,15 @@
 <?php
 
-namespace Drupal\color\Tests;
+namespace Drupal\Tests\color\Functional;
 
-use Drupal\simpletest\WebTestBase;
+use Drupal\Tests\BrowserTestBase;
 
 /**
  * Ensures the color config schema is correct.
  *
  * @group color
  */
-class ColorConfigSchemaTest extends WebTestBase {
+class ColorConfigSchemaTest extends BrowserTestBase {
 
   /**
    * Modules to install.
diff --git a/core/modules/color/src/Tests/ColorSafePreviewTest.php b/core/modules/color/test/src/Functional/ColorSafePreviewTest.php
similarity index 90%
rename from core/modules/color/src/Tests/ColorSafePreviewTest.php
rename to core/modules/color/test/src/Functional/ColorSafePreviewTest.php
index 813a92e..18b0534 100644
--- a/core/modules/color/src/Tests/ColorSafePreviewTest.php
+++ b/core/modules/color/test/src/Functional/ColorSafePreviewTest.php
@@ -1,16 +1,16 @@
 <?php
 
-namespace Drupal\color\Tests;
+namespace Drupal\Tests\color\Functional;
 
 use Drupal\Core\Url;
-use Drupal\simpletest\WebTestBase;
+use Drupal\Tests\BrowserTestBase;
 
 /**
  * Tests sanitizing color preview loaded from theme.
  *
  * @group Theme
  */
-class ColorSafePreviewTest extends WebTestBase {
+class ColorSafePreviewTest extends BrowserTestBase {
 
   /**
    * Modules to enable.
diff --git a/core/modules/color/src/Tests/ColorTest.php b/core/modules/color/test/src/Functional/ColorTest.php
similarity index 98%
rename from core/modules/color/src/Tests/ColorTest.php
rename to core/modules/color/test/src/Functional/ColorTest.php
index 578f7fb..dc44566 100644
--- a/core/modules/color/src/Tests/ColorTest.php
+++ b/core/modules/color/test/src/Functional/ColorTest.php
@@ -1,8 +1,8 @@
 <?php
 
-namespace Drupal\color\Tests;
+namespace Drupal\Tests\color\Functional;
 
-use Drupal\simpletest\WebTestBase;
+use Drupal\Tests\BrowserTestBase;
 
 /**
  * Modify the Bartik theme colors and make sure the changes are reflected on the
@@ -10,7 +10,7 @@
  *
  * @group color
  */
-class ColorTest extends WebTestBase {
+class ColorTest extends BrowserTestBase {
 
   /**
    * Modules to install.
diff --git a/core/tests/Drupal/FunctionalTests/AssertLegacyTrait.php b/core/tests/Drupal/FunctionalTests/AssertLegacyTrait.php
index 6ca9f85..5f5771c 100644
--- a/core/tests/Drupal/FunctionalTests/AssertLegacyTrait.php
+++ b/core/tests/Drupal/FunctionalTests/AssertLegacyTrait.php
@@ -204,6 +204,71 @@ protected function assertNoRaw($raw) {
   }
 
   /**
+   * Triggers a pass if the Perl regex pattern is found in the raw content.
+   *
+   * @param string $pattern
+   *   Perl regex to look for including the regex delimiters.
+   *
+   * @deprecated Scheduled for removal in Drupal 9.0.0.
+   *   Use $this->assertSession()->responseMatches() instead.
+   */
+  protected function assertPattern($pattern) {
+    $this->assertSession()->responseMatches($pattern);
+  }
+
+  /**
+   * Passes if the text is found ONLY ONCE on the text version of the page.
+   *
+   * The text version is the equivalent of what a user would see when viewing
+   * through a web browser. In other words the HTML has been filtered out of
+   * the contents.
+   *
+   * @param string|\Drupal\Component\Render\MarkupInterface $text
+   *   Plain text to look for.
+   */
+  protected function assertUniqueText($text) {
+    $this->assertUniqueTextHelper($text, TRUE);
+  }
+
+  /**
+   * Passes if the text is found MORE THAN ONCE on the text version of the page.
+   *
+   * The text version is the equivalent of what a user would see when viewing
+   * through a web browser. In other words the HTML has been filtered out of
+   * the contents.
+   *
+   * @param string|\Drupal\Component\Render\MarkupInterface $text
+   *   Plain text to look for.
+   */
+  protected function assertNoUniqueText($text) {
+    $this->assertUniqueTextHelper($text, FALSE);
+  }
+
+  /**
+   * Helper for assertUniqueText and assertNoUniqueText.
+   *
+   * It is not recommended to call this function directly.
+   *
+   * @param string|\Drupal\Component\Render\MarkupInterface $text
+   *   Plain text to look for.
+   * @param bool $be_unique
+   *   (optional) TRUE if this text should be found only once, FALSE if it
+   *   should be found more than once. Defaults to FALSE.
+   */
+  protected function assertUniqueTextHelper($text, $be_unique = FALSE) {
+    // Cast MarkupInterface objects to string.
+    $text = (string) $text;
+    $message = '"' . $text . '"' . ($be_unique ? ' found only once' : ' found more than once');
+    $first_occurrence = strpos($this->getTextContent(), $text);
+    if ($first_occurrence === FALSE) {
+      $this->assertTrue(FALSE, $message);
+    }
+    $offset = $first_occurrence + strlen($text);
+    $second_occurrence = strpos($this->getTextContent(), $text, $offset);
+    $this->assertTrue($be_unique == ($second_occurrence === FALSE), $message);
+  }
+
+  /**
    * Pass if the page title is the given string.
    *
    * @param string $expected_title
diff --git a/core/tests/Drupal/Tests/BrowserTestBase.php b/core/tests/Drupal/Tests/BrowserTestBase.php
index 3beb32f..f5efd29 100644
--- a/core/tests/Drupal/Tests/BrowserTestBase.php
+++ b/core/tests/Drupal/Tests/BrowserTestBase.php
@@ -7,6 +7,7 @@
 use Behat\Mink\Mink;
 use Behat\Mink\Session;
 use Drupal\Component\FileCache\FileCacheFactory;
+use Drupal\Component\Serialization\Json;
 use Drupal\Component\Serialization\Yaml;
 use Drupal\Component\Utility\Html;
 use Drupal\Component\Utility\SafeMarkup;
@@ -232,6 +233,15 @@
   protected $preserveGlobalState = FALSE;
 
   /**
+   * The drupalSettings value from the current raw $content.
+   *
+   * The drupalSettings refers to the drupalSettings JavaScript variable.
+   *
+   * @var array
+   */
+  protected $drupalSettings = [];
+
+  /**
    * Class name for HTML output logging.
    *
    * @var string
@@ -637,7 +647,11 @@ protected function drupalGet($path, array $options = array()) {
     $this->prepareRequest();
     $session->visit($url);
     $out = $session->getPage()->getContent();
-
+    // Store the drupalSettings JavaScript variable.
+    $this->drupalSettings = [];
+    if (preg_match('@<script type="application/json" data-drupal-selector="drupal-settings-json">([^<]*)</script>@', $out, $matches)) {
+      $this->drupalSettings = Json::decode($matches[1]);
+    }
     // Ensure that any changes to variables in the other thread are picked up.
     $this->refreshVariables();
 
@@ -941,11 +955,15 @@ protected function submitForm(array $edit, $submit, $form_html_id = NULL) {
     // Submit form.
     $this->prepareRequest();
     $submit_button->press();
-
+    // Store the drupalSettings JavaScript variable.
+    $out = $this->getSession()->getPage()->getContent();
+    $this->drupalSettings = [];
+    if (preg_match('@<script type="application/json" data-drupal-selector="drupal-settings-json">([^<]*)</script>@', $out, $matches)) {
+      $this->drupalSettings = Json::decode($matches[1]);
+    }
     // Ensure that any changes to variables in the other thread are picked up.
     $this->refreshVariables();
     if ($this->htmlOutputEnabled) {
-      $out = $this->getSession()->getPage()->getContent();
       $html_output = 'POST request to: ' . $action .
         '<hr />Ending URL: ' . $this->getSession()->getCurrentUrl();
       $html_output .= '<hr />' . $out;
@@ -1613,6 +1631,30 @@ public function __sleep() {
   }
 
   /**
+   * Gets the value of drupalSettings for the currently-loaded page.
+   *
+   * The drupalSettings refers to the drupalSettings JavaScript variable.
+   *
+   * @return array
+   *   The drupalSettings value from the current page.
+   */
+  protected function getDrupalSettings() {
+    return $this->drupalSettings;
+  }
+
+  /**
+   * Sets the value of drupalSettings for the currently-loaded page.
+   *
+   * The drupalSettings refers to the drupalSettings JavaScript variable.
+   *
+   * @param array $settings
+   *   The drupalSettings JavaScript variable.
+   */
+  protected function setDrupalSettings(array $settings) {
+    $this->drupalSettings = $settings;
+  }
+
+  /**
    * Logs a HTML output message in a text file.
    *
    * The link to the HTML output message will be printed by the results printer.