diff --git a/core/lib/Drupal/Component/Utility/Unicode.php b/core/lib/Drupal/Component/Utility/Unicode.php
index cf979d9..cd48373 100644
--- a/core/lib/Drupal/Component/Utility/Unicode.php
+++ b/core/lib/Drupal/Component/Utility/Unicode.php
@@ -99,6 +99,15 @@ class Unicode {
 
   /**
    * Get the current status of unicode/multibyte support on this enviroment.
+   *
+   * @return int
+   *   The status of multibyte support. It can be one of:
+   *   - \Drupal\Component\Utility\Unicode::STATUS_MULTIBYTE
+   *     Standard PHP (emulated) unicode support.
+   *   - \Drupal\Component\Utility\Unicode::STATUS_SINGLEBYTE
+   *     Full unicode support using an extension.
+   *   - \Drupal\Component\Utility\Unicode::STATUS_ERROR
+   *     An error occured. No unicode support.
    */
   public static function getStatus() {
     return static::$status;
@@ -107,16 +116,19 @@ public static function getStatus() {
   /**
    * Sets the value for multibyte support status for the current enviroment.
    *
-   * The following header keys are supported:
-   *   - Unicode::STATUS_MULTIBYTE: Standard PHP (emulated) unicode support.
-   *   - Unicode::STATUS_SINGLEBYTE: Full unicode support using an extension.
-   *   - Unicode::STATUS_ERROR: An error occured. No unicode support.
+   * The following status keys are supported:
+   *   - \Drupal\Component\Utility\Unicode::STATUS_MULTIBYTE
+   *     Standard PHP (emulated) unicode support.
+   *   - \Drupal\Component\Utility\Unicode::STATUS_SINGLEBYTE
+   *     Full unicode support using an extension.
+   *   - \Drupal\Component\Utility\Unicode::STATUS_ERROR
+   *     An error occured. No unicode support.
    *
    * @param int $status
    *   The new status of multibyte support.
    */
   public static function setStatus($status) {
-    if (!in_array($status, array(self::STATUS_SINGLEBYTE, self::STATUS_MULTIBYTE, self::STATUS_ERROR))) {
+    if (!in_array($status, array(static::STATUS_SINGLEBYTE, static::STATUS_MULTIBYTE, static::STATUS_ERROR))) {
       throw new \InvalidArgumentException('Invalid status value for unicode support.');
     }
     static::$status = $status;
@@ -259,9 +271,9 @@ public static function strtoupper($text) {
       return mb_strtoupper($text);
     }
     else {
-      // Use C-locale for ASCII-only uppercase
+      // Use C-locale for ASCII-only uppercase.
       $text = strtoupper($text);
-      // Case flip Latin-1 accented letters
+      // Case flip Latin-1 accented letters.
       $text = preg_replace_callback('/\xC3[\xA0-\xB6\xB8-\xBE]/', '\Drupal\Component\Utility\Unicode::caseFlip', $text);
       return $text;
     }
@@ -281,9 +293,9 @@ public static function strtolower($text) {
       return mb_strtolower($text);
     }
     else {
-      // Use C-locale for ASCII-only lowercase
+      // Use C-locale for ASCII-only lowercase.
       $text = strtolower($text);
-      // Case flip Latin-1 accented letters
+      // Case flip Latin-1 accented letters.
       $text = preg_replace_callback('/\xC3[\x80-\x96\x98-\x9E]/', '\Drupal\Component\Utility\Unicode::caseFlip', $text);
       return $text;
     }
diff --git a/core/tests/Drupal/Tests/Component/Utility/UnicodeTest.php b/core/tests/Drupal/Tests/Component/Utility/UnicodeTest.php
index 0b596a9..5f49a6d 100644
--- a/core/tests/Drupal/Tests/Component/Utility/UnicodeTest.php
+++ b/core/tests/Drupal/Tests/Component/Utility/UnicodeTest.php
@@ -45,6 +45,12 @@ public function testStatus($value, $expected, $invalid = FALSE) {
    * Data provider for testStatus().
    *
    * @see testStatus()
+   *
+   * @return array
+   *   An array containing:
+   *     - The status value to set.
+   *     - The status value to expect after setting the new value.
+   *     - (optional) Boolean indicating invalid status. Defaults to FALSE.
    */
   public function providerTestStatus() {
     return array(
@@ -72,6 +78,9 @@ public function testMimeHeader($value, $encoded) {
    * Data provider for testMimeHeader().
    *
    * @see testMimeHeader()
+   *
+   * @return array
+   *   An array containing a string and its encoded value.
    */
   public function providerTestMimeHeader() {
     return array(
@@ -95,6 +104,10 @@ public function testStrtolower($text, $expected, $multibyte = FALSE) {
    * Data provider for testStrtolower().
    *
    * @see testStrtolower()
+   *
+   * @return array
+   *   An array containing a string, its lowercase version and whether it should
+   *   be processed as multibyte.
    */
   public function providerStrtolower() {
     $cases = array(
@@ -126,6 +139,10 @@ public function testStrtoupper($text, $expected, $multibyte = FALSE) {
    * Data provider for testStrtoupper().
    *
    * @see testStrtoupper()
+   *
+   * @return array
+   *   An array containing a string, its uppercase version and whether it should
+   *   be processed as multibyte.
    */
   public function providerStrtoupper() {
     $cases = array(
@@ -155,6 +172,9 @@ public function testUcfirst($text, $expected) {
    * Data provider for testUcfirst().
    *
    * @see testUcfirst()
+   *
+   * @return array
+   *   An array containing a string and its uppercase first version.
    */
   public function providerUcfirst() {
     return array(
@@ -180,6 +200,9 @@ public function testStrlen($text, $expected) {
    * Data provider for testStrlen().
    *
    * @see testStrlen()
+   *
+   * @return array
+   *   An array containing a string and its length.
    */
   public function providerStrlen() {
     return array(
@@ -201,6 +224,13 @@ public function testSubstr($text, $start, $length, $expected) {
    * Data provider for testSubstr().
    *
    * @see testSubstr()
+   *
+   * @return array
+   *   An array containing:
+   *     - The string to test.
+   *     - The start number to be processed by substr.
+   *     - The length number to be processed by substr.
+   *     - The expected string result.
    */
   public function providerSubstr() {
     return array(
@@ -245,6 +275,14 @@ public function testTruncate($text, $max_length, $expected, $wordsafe = FALSE, $
    * Data provider for testTruncate().
    *
    * @see testTruncate()
+   *
+   * @return array
+   *   An array containing:
+   *     - The string to test.
+   *     - The max length to truncate this string to.
+   *     - The expected string result.
+   *     - (optional) Boolean for the $wordsafe flag. Defaults to FALSE.
+   *     - (optional) Boolean for the $add_ellipsis flag. Defaults to FALSE.
    */
   public function providerTruncate() {
     return array(