diff -u b/core/lib/Drupal/Component/Utility/Random.php b/core/lib/Drupal/Component/Utility/Random.php
--- b/core/lib/Drupal/Component/Utility/Random.php
+++ b/core/lib/Drupal/Component/Utility/Random.php
@@ -8,7 +8,7 @@
 namespace Drupal\Component\Utility;
 
 /**
- * Utility class for creating random data.
+ * Defines a utility class for creating random data.
  */
 class Random {
 
@@ -43,10 +43,6 @@
    * miscellaneous characters. Use this method when testing general input
    * where the content is not restricted.
    *
-   * Do not use this method when special characters are not possible (e.g., in
-   * machine or file names that have already been validated); instead, use
-   * \Drupal\Component\Utility\Random::name().
-   *
    * @param int $length
    *   Length of random string to generate.
    *
@@ -80,9 +76,6 @@
    * require machine readable values (i.e. without spaces and non-standard
    * characters) this method is best.
    *
-   * Do not use this method when testing unvalidated user input. Instead, use
-   * \Drupal\Component\Utility\Random::string().
-   *
    * @param int $length
    *   Length of random string to generate.
    *
diff -u b/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
--- b/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
@@ -1155,6 +1155,10 @@
   /**
    * Generates a unique random string of ASCII characters of codes 32 to 126.
    *
+   * Do not use this method when special characters are not possible (e.g., in
+   * machine or file names that have already been validated); instead, use
+   * \Drupal\simpletest\TestBase::randomName().
+   *
    * @param int $length
    *   Length of random string to generate.
    *
@@ -1170,6 +1174,9 @@
   /**
    * Generates a unique random string containing letters and numbers.
    *
+   * Do not use this method when testing unvalidated user input. Instead, use
+   * \Drupal\simpletest\TestBase::randomString().
+   *
    * @param int $length
    *   Length of random string to generate.
    *
diff -u b/core/tests/Drupal/Tests/Component/Utility/RandomTest.php b/core/tests/Drupal/Tests/Component/Utility/RandomTest.php
--- b/core/tests/Drupal/Tests/Component/Utility/RandomTest.php
+++ b/core/tests/Drupal/Tests/Component/Utility/RandomTest.php
@@ -11,7 +11,7 @@
 use Drupal\Tests\UnitTestCase;
 
 /**
- * Tests random data generating.
+ * Tests random data generation.
  *
  * @see \Drupal\Component\Utility\Random
  */
@@ -36,7 +36,7 @@
       $strings[$str] = TRUE;
     }
 
-    // There are less than 100 possibilities so an exception should occur to
+    // There are fewer than 100 possibilities so an exception should occur to
     // prevent infinite loops.
     $runtime_exception = FALSE;
     try {
@@ -63,7 +63,7 @@
       $names[$str] = TRUE;
     }
 
-    // There are less than 100 possibilities so an exception should occur to
+    // There are fewer than 100 possibilities so an exception should occur to
     // prevent infinite loops.
     $runtime_exception = FALSE;
     try {