diff --git a/core/tests/Drupal/Tests/Component/Utility/HtmlTest.php b/core/tests/Drupal/Tests/Component/Utility/HtmlTest.php
index a60ea90..18b07f7 100644
--- a/core/tests/Drupal/Tests/Component/Utility/HtmlTest.php
+++ b/core/tests/Drupal/Tests/Component/Utility/HtmlTest.php
@@ -210,4 +210,45 @@ public function providerTestHtmlGetId() {
     );
   }
 
+  /**
+   * Tests Html::decodeEntities().
+   *
+   * @dataProvider providerDecodeEntities
+   * @covers ::decodeEntities
+   */
+  public function testDecodeEntities($text, $expected) {
+    $this->assertEquals($expected, Html::decodeEntities($text));
+  }
+
+  /**
+   * Data provider for testDecodeEntities().
+   *
+   * @see testCheckPlain()
+   */
+  public function providerDecodeEntities() {
+    return array(
+      array('Drupal', 'Drupal'),
+      array('<script>', '<script>'),
+      array('&lt;script&gt;', '<script>'),
+      array('&#60;script&#62;', '<script>'),
+      array('&amp;lt;script&amp;gt;', '&lt;script&gt;'),
+      array('"', '"'),
+      array('&#34;', '"'),
+      array('&amp;#34;', '&#34;'),
+      array('&quot;', '"'),
+      array('&amp;quot;', '&quot;'),
+      array("'", "'"),
+      array('&#39;', "'"),
+      array('&amp;#39;', '&#39;'),
+      array('©', '©'),
+      array('&copy;', '©'),
+      array('&#169;', '©'),
+      array('→', '→'),
+      array('&#8594;', '→'),
+      array('➼', '➼'),
+      array('&#10172;', '➼'),
+      array('&euro;', '€'),
+    );
+  }
+
 }
diff --git a/core/tests/Drupal/Tests/Component/Utility/SafeMarkupTest.php b/core/tests/Drupal/Tests/Component/Utility/SafeMarkupTest.php
index eadc122..1e7d355 100644
--- a/core/tests/Drupal/Tests/Component/Utility/SafeMarkupTest.php
+++ b/core/tests/Drupal/Tests/Component/Utility/SafeMarkupTest.php
@@ -45,7 +45,7 @@ public function testSet($text, $message) {
    */
   public function providerSet() {
     // Checks that invalid multi-byte sequences are rejected.
-    $tests[] = array("Foo\xC0barbaz", '', 'String::checkPlain() rejects invalid sequence "Foo\xC0barbaz"', TRUE);
+    $tests[] = array("Foo\xC0barbaz", '', 'SafeMarkup::checkPlain() rejects invalid sequence "Foo\xC0barbaz"', TRUE);
     $tests[] = array("Fooÿñ", 'SafeMarkup::set() accepts valid sequence "Fooÿñ"');
     $tests[] = array(new TextWrapper("Fooÿñ"), 'SafeMarkup::set() accepts valid sequence "Fooÿñ" in an object implementing __toString()');
     $tests[] = array("<div>", 'SafeMarkup::set() accepts HTML');
@@ -101,4 +101,91 @@ public function testInvalidSetMultiple() {
     SafeMarkup::setMultiple($texts);
   }
 
+  /**
+   * Tests SafeMarkup::checkPlain().
+   *
+   * @dataProvider providerCheckPlain
+   * @covers ::checkPlain
+   *
+   * @param string $text
+   *   The text to provide to SafeMarkup::checkPlain().
+   * @param string $expected
+   *   The expected output from the function.
+   * @param string $message
+   *   The message to provide as output for the test.
+   * @param bool $ignorewarnings
+   *   Whether or not to ignore PHP 5.3+ invalid multibyte sequence warnings.
+   */
+  function testCheckPlain($text, $expected, $message, $ignorewarnings = FALSE) {
+    $result = $ignorewarnings ? @SafeMarkup::checkPlain($text) : SafeMarkup::checkPlain($text);
+    $this->assertEquals($expected, $result, $message);
+  }
+
+  /**
+   * Data provider for testCheckPlain().
+   *
+   * @see testCheckPlain()
+   */
+  function providerCheckPlain() {
+    // Checks that invalid multi-byte sequences are rejected.
+    $tests[] = array("Foo\xC0barbaz", '', 'SafeMarkup::checkPlain() rejects invalid sequence "Foo\xC0barbaz"', TRUE);
+    $tests[] = array("\xc2\"", '', 'SafeMarkup::checkPlain() rejects invalid sequence "\xc2\""', TRUE);
+    $tests[] = array("Fooÿñ", "Fooÿñ", 'SafeMarkup::checkPlain() accepts valid sequence "Fooÿñ"');
+
+    // Checks that special characters are escaped.
+    $tests[] = array("<script>", '&lt;script&gt;', 'SafeMarkup::checkPlain() escapes &lt;script&gt;');
+    $tests[] = array('<>&"\'', '&lt;&gt;&amp;&quot;&#039;', 'SafeMarkup::checkPlain() escapes reserved HTML characters.');
+
+    return $tests;
+  }
+
+  /**
+   * Tests string formatting with SafeMarkup::format().
+   *
+   * @dataProvider providerFormat
+   * @covers ::format
+   *
+   * @param string $string
+   *   The string to run through SafeMarkup::format().
+   * @param string $args
+   *   The arguments to pass into SafeMarkup::format().
+   * @param string $expected
+   *   The expected result from calling the function.
+   * @param string $message
+   *   The message to display as output to the test.
+   * @param bool $expected_is_safe
+   *   Whether the result is expected to be safe for HTML display.
+   */
+  function testFormat($string, $args, $expected, $message, $expected_is_safe) {
+    $result = SafeMarkup::format($string, $args);
+    $this->assertEquals($expected, $result, $message);
+    $this->assertEquals($expected_is_safe, SafeMarkup::isSafe($result), 'SafeMarkup::format correctly sets the result as safe or not safe.');
+  }
+
+  /**
+   * Data provider for testFormat().
+   *
+   * @see testFormat()
+   */
+  function providerFormat() {
+    $tests[] = array('Simple text', array(), 'Simple text', 'SafeMarkup::format leaves simple text alone.', TRUE);
+    $tests[] = array('Escaped text: @value', array('@value' => '<script>'), 'Escaped text: &lt;script&gt;', 'SafeMarkup::format replaces and escapes string.', TRUE);
+    $tests[] = array('Escaped text: @value', array('@value' => SafeMarkup::set('<span>Safe HTML</span>')), 'Escaped text: <span>Safe HTML</span>', 'SafeMarkup::format does not escape an already safe string.', TRUE);
+    $tests[] = array('Placeholder text: %value', array('%value' => '<script>'), 'Placeholder text: <em class="placeholder">&lt;script&gt;</em>', 'SafeMarkup::format replaces, escapes and themes string.', TRUE);
+    $tests[] = array('Placeholder text: %value', array('%value' => SafeMarkup::set('<span>Safe HTML</span>')), 'Placeholder text: <em class="placeholder"><span>Safe HTML</span></em>', 'SafeMarkup::format does not escape an already safe string themed as a placeholder.', TRUE);
+    $tests[] = array('Verbatim text: !value', array('!value' => '<script>'), 'Verbatim text: <script>', 'SafeMarkup::format replaces verbatim string as-is.', FALSE);
+    $tests[] = array('Verbatim text: !value', array('!value' => SafeMarkup::set('<span>Safe HTML</span>')), 'Verbatim text: <span>Safe HTML</span>', 'SafeMarkup::format replaces verbatim string as-is.', TRUE);
+
+    return $tests;
+  }
+
+  /**
+   * Tests SafeMarkup::placeholder().
+   *
+   * @covers ::placeholder
+   */
+  function testPlaceholder() {
+    $this->assertEquals('<em class="placeholder">Some text</em>', SafeMarkup::placeholder('Some text'));
+  }
+
 }
diff --git a/core/tests/Drupal/Tests/Component/Utility/StringTest.php b/core/tests/Drupal/Tests/Component/Utility/StringTest.php
deleted file mode 100644
index 307385a..0000000
--- a/core/tests/Drupal/Tests/Component/Utility/StringTest.php
+++ /dev/null
@@ -1,151 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\Tests\Component\Utility\StringTest.
- */
-
-namespace Drupal\Tests\Component\Utility;
-
-use Drupal\Component\Utility\SafeMarkup;
-use Drupal\Tests\UnitTestCase;
-use Drupal\Component\Utility\String;
-
-/**
- * Tests string filtering.
- *
- * @group Utility
- *
- * @coversDefaultClass \Drupal\Component\Utility\String
- */
-class StringTest extends UnitTestCase {
-
-  /**
-   * Tests String::checkPlain().
-   *
-   * @dataProvider providerCheckPlain
-   * @covers ::checkPlain
-   *
-   * @param string $text
-   *   The text to provide to String::checkPlain().
-   * @param string $expected
-   *   The expected output from the function.
-   * @param string $message
-   *   The message to provide as output for the test.
-   * @param bool $ignorewarnings
-   *   Whether or not to ignore PHP 5.3+ invalid multibyte sequence warnings.
-   */
-  function testCheckPlain($text, $expected, $message, $ignorewarnings = FALSE) {
-    $result = $ignorewarnings ? @String::checkPlain($text) : String::checkPlain($text);
-    $this->assertEquals($expected, $result, $message);
-  }
-
-  /**
-   * Data provider for testCheckPlain().
-   *
-   * @see testCheckPlain()
-   */
-  function providerCheckPlain() {
-    // Checks that invalid multi-byte sequences are rejected.
-    $tests[] = array("Foo\xC0barbaz", '', 'String::checkPlain() rejects invalid sequence "Foo\xC0barbaz"', TRUE);
-    $tests[] = array("\xc2\"", '', 'String::checkPlain() rejects invalid sequence "\xc2\""', TRUE);
-    $tests[] = array("Fooÿñ", "Fooÿñ", 'String::checkPlain() accepts valid sequence "Fooÿñ"');
-
-    // Checks that special characters are escaped.
-    $tests[] = array("<script>", '&lt;script&gt;', 'String::checkPlain() escapes &lt;script&gt;');
-    $tests[] = array('<>&"\'', '&lt;&gt;&amp;&quot;&#039;', 'String::checkPlain() escapes reserved HTML characters.');
-
-    return $tests;
-  }
-
-  /**
-   * Tests string formatting with String::format().
-   *
-   * @dataProvider providerFormat
-   * @covers ::format
-   *
-   * @param string $string
-   *   The string to run through String::format().
-   * @param string $args
-   *   The arguments to pass into String::format().
-   * @param string $expected
-   *   The expected result from calling the function.
-   * @param string $message
-   *   The message to display as output to the test.
-   * @param bool $expected_is_safe
-   *   Whether the result is expected to be safe for HTML display.
-   */
-  function testFormat($string, $args, $expected, $message, $expected_is_safe) {
-    $result = String::format($string, $args);
-    $this->assertEquals($expected, $result, $message);
-    $this->assertEquals($expected_is_safe, SafeMarkup::isSafe($result), 'String::format correctly sets the result as safe or not safe.');
-  }
-
-  /**
-   * Data provider for testFormat().
-   *
-   * @see testFormat()
-   */
-  function providerFormat() {
-    $tests[] = array('Simple text', array(), 'Simple text', 'String::format leaves simple text alone.', TRUE);
-    $tests[] = array('Escaped text: @value', array('@value' => '<script>'), 'Escaped text: &lt;script&gt;', 'String::format replaces and escapes string.', TRUE);
-    $tests[] = array('Escaped text: @value', array('@value' => SafeMarkup::set('<span>Safe HTML</span>')), 'Escaped text: <span>Safe HTML</span>', 'String::format does not escape an already safe string.', TRUE);
-    $tests[] = array('Placeholder text: %value', array('%value' => '<script>'), 'Placeholder text: <em class="placeholder">&lt;script&gt;</em>', 'String::format replaces, escapes and themes string.', TRUE);
-    $tests[] = array('Placeholder text: %value', array('%value' => SafeMarkup::set('<span>Safe HTML</span>')), 'Placeholder text: <em class="placeholder"><span>Safe HTML</span></em>', 'String::format does not escape an already safe string themed as a placeholder.', TRUE);
-    $tests[] = array('Verbatim text: !value', array('!value' => '<script>'), 'Verbatim text: <script>', 'String::format replaces verbatim string as-is.', FALSE);
-    $tests[] = array('Verbatim text: !value', array('!value' => SafeMarkup::set('<span>Safe HTML</span>')), 'Verbatim text: <span>Safe HTML</span>', 'String::format replaces verbatim string as-is.', TRUE);
-
-    return $tests;
-  }
-
-  /**
-   * Tests String::placeholder().
-   *
-   * @covers ::placeholder
-   */
-  function testPlaceholder() {
-    $this->assertEquals('<em class="placeholder">Some text</em>', String::placeholder('Some text'));
-  }
-
-  /**
-   * Tests String::decodeEntities().
-   *
-   * @dataProvider providerDecodeEntities
-   * @covers ::decodeEntities
-   */
-  public function testDecodeEntities($text, $expected) {
-    $this->assertEquals($expected, String::decodeEntities($text));
-  }
-
-  /**
-   * Data provider for testDecodeEntities().
-   *
-   * @see testCheckPlain()
-   */
-  public function providerDecodeEntities() {
-    return array(
-      array('Drupal', 'Drupal'),
-      array('<script>', '<script>'),
-      array('&lt;script&gt;', '<script>'),
-      array('&#60;script&#62;', '<script>'),
-      array('&amp;lt;script&amp;gt;', '&lt;script&gt;'),
-      array('"', '"'),
-      array('&#34;', '"'),
-      array('&amp;#34;', '&#34;'),
-      array('&quot;', '"'),
-      array('&amp;quot;', '&quot;'),
-      array("'", "'"),
-      array('&#39;', "'"),
-      array('&amp;#39;', '&#39;'),
-      array('©', '©'),
-      array('&copy;', '©'),
-      array('&#169;', '©'),
-      array('→', '→'),
-      array('&#8594;', '→'),
-      array('➼', '➼'),
-      array('&#10172;', '➼'),
-      array('&euro;', '€'),
-    );
-  }
-
-}