diff --git a/core/lib/Drupal/Core/Config/Testing/ConfigSchemaChecker.php b/core/lib/Drupal/Core/Config/Testing/ConfigSchemaChecker.php
index 1c5b043..421071b 100644
--- a/core/lib/Drupal/Core/Config/Testing/ConfigSchemaChecker.php
+++ b/core/lib/Drupal/Core/Config/Testing/ConfigSchemaChecker.php
@@ -13,8 +13,6 @@
 use Drupal\Core\Config\Schema\SchemaCheckTrait;
 use Drupal\Core\Config\Schema\SchemaIncompleteException;
 use Drupal\Core\Config\TypedConfigManagerInterface;
-use Drupal\Core\Database\ConnectionNotDefinedException;
-use Drupal\Core\Database\Database;
 use Symfony\Component\EventDispatcher\EventSubscriberInterface;
 
 /**
@@ -55,15 +53,16 @@ public function __construct(TypedConfigManagerInterface $typed_manager) {
   }
 
   /**
-   * Removes stale static cache entries when configuration is saved.
+   * Checks that configuration complies with its schema on config save.
    *
    * @param ConfigCrudEvent $event
    *   The configuration event.
+   *
+   * @throws \Drupal\Core\Config\Schema\SchemaIncompleteException
+   *   Exception thrown when configuration does not match its schema.
    */
   public function onConfigSave(ConfigCrudEvent $event) {
     $saved_config = $event->getConfig();
-    // Check that we have a valid for all config saved during tests. Do not
-    // validate the same config / data.
     $name = $saved_config->getName();
     $data = $saved_config->get();
     $checksum = crc32(serialize($data));
diff --git a/core/modules/config/src/Tests/SchemaConfigListenerTest.php b/core/modules/config/src/Tests/SchemaConfigListenerTest.php
index 070e268..4796547 100644
--- a/core/modules/config/src/Tests/SchemaConfigListenerTest.php
+++ b/core/modules/config/src/Tests/SchemaConfigListenerTest.php
@@ -31,7 +31,7 @@ class SchemaConfigListenerTest extends KernelTestBase {
   /**
    * Tests \Drupal\Core\Config\Testing\ConfigSchemaChecker.
    */
-  public function testTrait() {
+  public function testConfigSchemaChecker() {
     // Test a non existing schema.
     $msg = 'Expected SchemaIncompleteException thrown';
     try {
@@ -43,6 +43,7 @@ public function testTrait() {
       $this->assertEqual('No schema for config_schema_test.noschema', $e->getMessage());
     }
 
+    // Test a valid schema.
     $msg = 'Unexpected SchemaIncompleteException thrown';
     $config = \Drupal::config('config_test.types')->set('int', 10);
     try {
@@ -53,6 +54,7 @@ public function testTrait() {
       $this->fail($msg);
     }
 
+    // Test an invalid schema.
     $msg = 'Expected SchemaIncompleteException thrown';
     $config = \Drupal::config('config_test.types')
       ->set('foo', 'bar')
diff --git a/core/modules/config/src/Tests/SchemaConfigListenerWebTest.php b/core/modules/config/src/Tests/SchemaConfigListenerWebTest.php
index d38b055..86e28d9 100644
--- a/core/modules/config/src/Tests/SchemaConfigListenerWebTest.php
+++ b/core/modules/config/src/Tests/SchemaConfigListenerWebTest.php
@@ -32,7 +32,7 @@ class SchemaConfigListenerWebTest extends WebTestBase {
   /**
    * Tests \Drupal\Core\Config\Testing\ConfigSchemaChecker.
    */
-  public function testTrait() {
+  public function testConfigSchemaChecker() {
     // Test a non existing schema.
     $msg = 'Expected SchemaIncompleteException thrown';
     try {
@@ -44,6 +44,7 @@ public function testTrait() {
       $this->assertEqual('No schema for config_schema_test.noschema', $e->getMessage());
     }
 
+    // Test a valid schema.
     $msg = 'Unexpected SchemaIncompleteException thrown';
     $config = \Drupal::config('config_test.types')->set('int', 10);
     try {
@@ -54,6 +55,7 @@ public function testTrait() {
       $this->fail($msg);
     }
 
+    // Test an invalid schema.
     $msg = 'Expected SchemaIncompleteException thrown';
     $config = \Drupal::config('config_test.types')
       ->set('foo', 'bar')
@@ -67,6 +69,7 @@ public function testTrait() {
       $this->pass('Schema errors for config_test.types with the following errors: config_test.types:foo: Missing schema., config_test.types:array: Variable type is integer but applied schema class is Drupal\Core\Config\Schema\Sequence.');
     }
 
+    // Test that the config event listener is working in the child site.
     $this->drupalGet('config_test/schema_listener');
     $this->assertText('No schema for config_schema_test.noschema');
   }