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
@@ -1209,26 +1209,26 @@
    *
    * @see \Drupal\Component\Utility\Random::string()
    *
-   * @param string $str
+   * @param string $string
    *   The random string to validate.
    *
    * @return bool
    *   TRUE if the random string is valid, FALSE if not.
    */
-  public function randomStringValidate($str) {
+  public function randomStringValidate($string) {
     // Consecutive spaces causes issues for
     // Drupal\simpletest\WebTestBase::assertLink().
-    if (preg_match('/\s{2,}/', $str)) {
+    if (preg_match('/\s{2,}/', $string)) {
       return FALSE;
     }
 
     // Starting with a space means that length might not be what is expected.
-    if (preg_match('/^\s/', $str)) {
+    if (preg_match('/^\s/', $string)) {
       return FALSE;
     }
 
     // Ending with a space means that length might not be what is expected.
-    if (preg_match('/\s$/', $str)) {
+    if (preg_match('/\s$/', $string)) {
       return FALSE;
     }
 
diff -u b/core/modules/simpletest/tests/Drupal/simpletest/Tests/TestBaseTest.php b/core/modules/simpletest/tests/Drupal/simpletest/Tests/TestBaseTest.php
--- b/core/modules/simpletest/tests/Drupal/simpletest/Tests/TestBaseTest.php
+++ b/core/modules/simpletest/tests/Drupal/simpletest/Tests/TestBaseTest.php
@@ -54,7 +54,7 @@
   /**
    * Tests the random strings validation rules.
    *
-   * @param string $str
+   * @param string $string
    *   The string to validate.
    * @param bool $expected
    *   The expected result of the validation.
@@ -63,8 +63,8 @@
    *
    * @dataProvider randomStringValidateProvider
    */
-  public function testRandomStringValidate($str, $expected) {
-    $actual = $this->stub->randomStringValidate($str);
+  public function testRandomStringValidate($string, $expected) {
+    $actual = $this->stub->randomStringValidate($string);
     $this->assertEquals($expected, $actual);
   }
 
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
@@ -162,15 +162,15 @@
    * @see \Drupal\Component\Utility\Random::name()
    * @see \Drupal\Tests\Component\Utility\RandomTest::testRandomStringValidator()
    *
-   * @param string $str
+   * @param string $string
    *   The random string to validate.
    *
    * @return bool
    *   TRUE if the random string is valid, FALSE if not.
    */
-  public function _RandomStringValidate($str) {
+  public function _RandomStringValidate($string) {
     if (empty($this->firstStringGenerated)) {
-      $this->firstStringGenerated = $str;
+      $this->firstStringGenerated = $string;
       return FALSE;
     }
     return TRUE;