diff --git a/core/modules/simpletest/src/KernelTestBase.php b/core/modules/simpletest/src/KernelTestBase.php
index e536ec3..62867e1 100644
--- a/core/modules/simpletest/src/KernelTestBase.php
+++ b/core/modules/simpletest/src/KernelTestBase.php
@@ -579,4 +579,20 @@ protected function render(array &$elements) {
     return $content;
   }
 
+  /**
+   * Changes in memory settings.
+   *
+   * @param $name
+   *   The name of the setting to return.
+   * @param $value
+   *   The value of the setting.
+   *
+   * @see \Drupal\Core\Site\Settings::get()
+   */
+  protected function settingsSet($name, $value) {
+    $settings = Settings::getAll();
+    $settings[$name] = $value;
+    new Settings($settings);
+  }
+
 }
diff --git a/core/modules/simpletest/src/TestBase.php b/core/modules/simpletest/src/TestBase.php
index 1e59712..40c8c4d 100644
--- a/core/modules/simpletest/src/TestBase.php
+++ b/core/modules/simpletest/src/TestBase.php
@@ -1393,22 +1393,6 @@ protected function exceptionHandler($exception) {
   }
 
   /**
-   * Changes in memory settings.
-   *
-   * @param $name
-   *   The name of the setting to return.
-   * @param $value
-   *   The value of the setting.
-   *
-   * @see \Drupal\Core\Site\Settings::get()
-   */
-  protected function settingsSet($name, $value) {
-    $settings = Settings::getAll();
-    $settings[$name] = $value;
-    new Settings($settings);
-  }
-
-  /**
    * Converts a list of possible parameters into a stack of permutations.
    *
    * Takes a list of parameters containing possible values, and converts all of
diff --git a/core/modules/simpletest/src/WebTestBase.php b/core/modules/simpletest/src/WebTestBase.php
index 5e86826..28fdc84 100644
--- a/core/modules/simpletest/src/WebTestBase.php
+++ b/core/modules/simpletest/src/WebTestBase.php
@@ -1144,9 +1144,6 @@ protected function writeCustomTranslations() {
     foreach ($this->customTranslations as $langcode => $values) {
       $settings_key = 'locale_custom_strings_' . $langcode;
 
-      // Update in-memory settings directly.
-      $this->settingsSet($settings_key, $values);
-
       $settings['settings'][$settings_key] = (object) array(
         'value' => $values,
         'required' => TRUE,
diff --git a/core/modules/system/src/Tests/Common/FormatDateTest.php b/core/modules/system/src/Tests/Common/FormatDateTest.php
index 0ece458..e24d644 100644
--- a/core/modules/system/src/Tests/Common/FormatDateTest.php
+++ b/core/modules/system/src/Tests/Common/FormatDateTest.php
@@ -43,7 +43,7 @@ protected function setUp() {
     $formats['short']->setPattern('Y M j - g:ia')->save();
     $this->refreshVariables();
 
-    $this->settingsSet('locale_custom_strings_' . self::LANGCODE, array(
+    $this->writeSettings('locale_custom_strings_' . self::LANGCODE, array(
       '' => array('Sunday' => 'domingo'),
       'Long month name' => array('March' => 'marzo'),
     ));
diff --git a/core/modules/system/src/Tests/Session/SessionTest.php b/core/modules/system/src/Tests/Session/SessionTest.php
index c194c79..533d33e 100644
--- a/core/modules/system/src/Tests/Session/SessionTest.php
+++ b/core/modules/system/src/Tests/Session/SessionTest.php
@@ -242,7 +242,7 @@ function testSessionWrite() {
     $this->assertEqual($times4->timestamp, $times3->timestamp, 'Sessions table was not updated.');
 
     // Force updating of users and sessions table once per second.
-    $this->settingsSet('session_write_interval', 0);
+    $this->writeSettings('session_write_interval', 0);
     // Write that value also into the test settings.php file.
     $settings['settings']['session_write_interval'] = (object) array(
       'value' => 0,