diff --git a/core/modules/color/tests/src/Functional/ColorTest.php b/core/modules/color/tests/src/Functional/ColorTest.php
index bb7d6fa..dc44566 100644
--- a/core/modules/color/tests/src/Functional/ColorTest.php
+++ b/core/modules/color/tests/src/Functional/ColorTest.php
@@ -108,7 +108,7 @@ function _testColor($theme, $test_values) {
     $this->drupalLogin($this->bigUser);
     $this->drupalGet($settings_path);
     $this->assertResponse(200);
-    $this->assertSession()->assertUniqueText('Color set');
+    $this->assertUniqueText('Color set');
     $edit['scheme'] = '';
     $edit[$test_values['palette_input']] = '#123456';
     $this->drupalPostForm($settings_path, $edit, t('Save configuration'));
@@ -116,9 +116,9 @@ function _testColor($theme, $test_values) {
     $this->drupalGet('<front>');
     $stylesheets = $this->config('color.theme.' . $theme)->get('stylesheets');
     foreach ($stylesheets as $stylesheet) {
-      $this->assertSession()->responseMatches('|' . file_url_transform_relative(file_create_url($stylesheet)) . '|');
+      $this->assertPattern('|' . file_url_transform_relative(file_create_url($stylesheet)) . '|', 'Make sure the color stylesheet is included in the content. (' . $theme . ')');
       $stylesheet_content = join("\n", file($stylesheet));
-      $this->assertTrue(strpos($stylesheet_content, 'color: #123456') !== FALSE);
+      $this->assertTrue(strpos($stylesheet_content, 'color: #123456') !== FALSE, 'Make sure the color we changed is in the color stylesheet. (' . $theme . ')');
     }
 
     $this->drupalGet($settings_path);
@@ -130,7 +130,7 @@ function _testColor($theme, $test_values) {
     $stylesheets = $this->config('color.theme.' . $theme)->get('stylesheets');
     foreach ($stylesheets as $stylesheet) {
       $stylesheet_content = join("\n", file($stylesheet));
-      $this->assertTrue(strpos($stylesheet_content, 'color: ' . $test_values['scheme_color']) !== FALSE);
+      $this->assertTrue(strpos($stylesheet_content, 'color: ' . $test_values['scheme_color']) !== FALSE, 'Make sure the color we changed is in the color stylesheet. (' . $theme . ')');
     }
 
     // Test with aggregated CSS turned on.
@@ -143,7 +143,7 @@ function _testColor($theme, $test_values) {
     foreach ($stylesheets as $uri) {
       $stylesheet_content .= join("\n", file(drupal_realpath($uri)));
     }
-    $this->assertTrue(strpos($stylesheet_content, 'public://') === FALSE);
+    $this->assertTrue(strpos($stylesheet_content, 'public://') === FALSE, 'Make sure the color paths have been translated to local paths. (' . $theme . ')');
     $config->set('css.preprocess', 0);
     $config->save();
   }
@@ -202,8 +202,8 @@ function testOverrideAndResetScheme() {
     $this->drupalPlaceBlock('system_branding_block', ['region' => 'header']);
 
     $this->drupalGet('');
-    $this->assertNoRaw('files/color/bartik-');
-    $this->assertRaw('bartik/logo.svg');
+    $this->assertNoRaw('files/color/bartik-', 'Make sure the color logo is not being used.');
+    $this->assertRaw('bartik/logo.svg', 'Make sure the original bartik logo exists.');
 
     // Log in and set the color scheme to 'slate'.
     $this->drupalLogin($this->bigUser);
@@ -213,8 +213,8 @@ function testOverrideAndResetScheme() {
     // Visit the homepage and ensure color changes.
     $this->drupalLogout();
     $this->drupalGet('');
-    $this->assertRaw('files/color/bartik-');
-    $this->assertNoRaw('bartik/logo.svg');
+    $this->assertRaw('files/color/bartik-', 'Make sure the color logo is being used.');
+    $this->assertNoRaw('bartik/logo.svg', 'Make sure the original bartik logo does not exist.');
 
     // Log in and set the color scheme back to default (delete config).
     $this->drupalLogin($this->bigUser);
@@ -224,8 +224,8 @@ function testOverrideAndResetScheme() {
     // Log out and ensure there is no color and we have the original logo.
     $this->drupalLogout();
     $this->drupalGet('');
-    $this->assertNoRaw('files/color/bartik-');
-    $this->assertRaw('bartik/logo.svg');
+    $this->assertNoRaw('files/color/bartik-', 'Make sure the color logo is not being used.');
+    $this->assertRaw('bartik/logo.svg', 'Make sure the original bartik logo exists.');
   }
 
 }
diff --git a/core/tests/Drupal/FunctionalTests/AssertLegacyTrait.php b/core/tests/Drupal/FunctionalTests/AssertLegacyTrait.php
index 6ca9f85..700af58 100644
--- a/core/tests/Drupal/FunctionalTests/AssertLegacyTrait.php
+++ b/core/tests/Drupal/FunctionalTests/AssertLegacyTrait.php
@@ -204,6 +204,76 @@ protected function assertNoRaw($raw) {
   }
 
   /**
+   * 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.
+   * @param string $message
+   *   (optional) A message to display with the assertion. Do not translate
+   *   messages with t(). If left blank, a default message will be displayed.
+   *
+   * @deprecated Scheduled for removal in Drupal 9.0.0.
+   *   Use $this->getSession()->getPage()->getText() and substr_count() instead.
+   */
+  protected function assertUniqueText($text, $message = NULL) {
+    // Cast MarkupInterface objects to string.
+    $text = (string) $text;
+
+    $message = $message ?: "'$text' found only once on the page";
+    $page_text = $this->getSession()->getPage()->getText();
+    $occurrences = substr_count($page_text, $text);
+    $this->assertSame(1, $occurrences, $message);
+  }
+
+  /**
+   * 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.
+   * @param string $message
+   *   (optional) A message to display with the assertion. Do not translate
+   *   messages with t(). If left blank, a default message will be displayed.
+   *
+   * @deprecated Scheduled for removal in Drupal 9.0.0.
+   *   Use $this->getSession()->getPage()->getText() and substr_count() instead.
+   */
+  protected function assertNoUniqueText($text, $message = '') {
+    // Cast MarkupInterface objects to string.
+    $text = (string) $text;
+
+    $message = $message ?: "'$text' found more than once on the page";
+    $page_text = $this->getSession()->getPage()->getText();
+    $occurrences = substr_count($page_text, $text);
+    $this->assertGreaterThan(1, $occurrences, $message);
+  }
+
+  /**
+   * 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.
+   * @param string $message
+   *   (optional) A message to display with the assertion. Do not translate
+   *   messages: use \Drupal\Component\Utility\SafeMarkup::format() to embed
+   *   variables in the message text, not t(). If left blank, a default message
+   *   will be displayed.
+   *
+   * @deprecated Scheduled for removal in Drupal 9.0.0.
+   *   Use $this->assertSession()->responseMatches() instead.
+   */
+  protected function assertPattern($pattern, $message = '') {
+    $this->assertSession()->responseMatches($pattern);
+  }
+
+  /**
    * Pass if the page title is the given string.
    *
    * @param string $expected_title
diff --git a/core/tests/Drupal/Tests/WebAssert.php b/core/tests/Drupal/Tests/WebAssert.php
index cc801bd..6156dda 100644
--- a/core/tests/Drupal/Tests/WebAssert.php
+++ b/core/tests/Drupal/Tests/WebAssert.php
@@ -422,55 +422,4 @@ public function fieldDisabled($field, TraversableElement $container = NULL)  {
     return $node;
   }
 
-  /**
-   * 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 $text
-   *   Plain text to look for.
-   */
-  public function assertUniqueText($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 $text
-   *   Plain text to look for.
-   */
-  public function assertNoUniqueText($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');
-    $content = $this->session->getPage()->getContent();
-    $first_occurrence = strpos($content, $text);
-    $this->assert($first_occurrence !== FALSE, $message);
-    $offset = $first_occurrence + strlen($text);
-    $second_occurrence = strpos($content, $text, $offset);
-    $this->assert($be_unique === ($second_occurrence === FALSE), $message);
-  }
-
 }