diff --git a/core/modules/field/tests/src/Functional/reEnableModuleFieldTest.php b/core/modules/field/tests/src/Functional/ReEnableModuleFieldTest.php
similarity index 98%
rename from core/modules/field/tests/src/Functional/reEnableModuleFieldTest.php
rename to core/modules/field/tests/src/Functional/ReEnableModuleFieldTest.php
index 51f2523225716af9a0f9308a9030953ca448e867..6855f6b9ceaaade4641c213c0aa902cfa410ce45 100644
--- a/core/modules/field/tests/src/Functional/reEnableModuleFieldTest.php
+++ b/core/modules/field/tests/src/Functional/ReEnableModuleFieldTest.php
@@ -12,7 +12,7 @@
  *
  * @group field
  */
-class reEnableModuleFieldTest extends BrowserTestBase {
+class ReEnableModuleFieldTest extends BrowserTestBase {
 
   use CronRunTrait;
 
diff --git a/core/phpcs.xml.dist b/core/phpcs.xml.dist
index bb295b599e0f6383c32c9d077b4a54459191e993..91b150c4aa582ddc8d28e9585e71e9c6adb2db50 100644
--- a/core/phpcs.xml.dist
+++ b/core/phpcs.xml.dist
@@ -158,6 +158,7 @@
       <property name="checkClosures" value="true"/>
     </properties>
   </rule>
+  <rule ref="Drupal.NamingConventions.ValidClassName"/>
   <rule ref="Generic.NamingConventions.ConstructorName"/>
   <rule ref="Generic.NamingConventions.UpperCaseConstantName"/>
   <rule ref="Generic.PHP.DeprecatedFunctions"/>
diff --git a/core/tests/Drupal/Tests/Core/DependencyInjection/ContainerBuilderTest.php b/core/tests/Drupal/Tests/Core/DependencyInjection/ContainerBuilderTest.php
index 03a16ccc7cb0e0e55b135bbb095accee968eefe2..193741f8e09b43fb832b60b083b70d2cc0e21fe2 100644
--- a/core/tests/Drupal/Tests/Core/DependencyInjection/ContainerBuilderTest.php
+++ b/core/tests/Drupal/Tests/Core/DependencyInjection/ContainerBuilderTest.php
@@ -131,7 +131,7 @@ public function testSerialize() {
    * @preserveGlobalState disabled
    */
   public function testConstructor() {
-    class_alias(testInterface::class, 'Symfony\Component\Config\Resource\ResourceInterface');
+    class_alias(TestInterface::class, 'Symfony\Component\Config\Resource\ResourceInterface');
     $container = new ContainerBuilder();
     $this->assertFalse($container->isTrackingResources());
   }
@@ -143,5 +143,5 @@ class_alias(testInterface::class, 'Symfony\Component\Config\Resource\ResourceInt
  *
  * @see \Drupal\Tests\Core\DependencyInjection\ContainerBuilderTest::testConstructor()
  */
-interface testInterface {
+interface TestInterface {
 }
diff --git a/core/tests/Drupal/Tests/Core/DrupalKernel/DrupalKernelTest.php b/core/tests/Drupal/Tests/Core/DrupalKernel/DrupalKernelTest.php
index efdfe3e7831eb509f710af392ad9a132aac4d119..e77d2e25eb75aaaad6ebce25974e573f4aea6a29 100644
--- a/core/tests/Drupal/Tests/Core/DrupalKernel/DrupalKernelTest.php
+++ b/core/tests/Drupal/Tests/Core/DrupalKernel/DrupalKernelTest.php
@@ -141,7 +141,7 @@ public function testFindSitePath() {
   /**
    * A fake autoloader for testing
    */
-  class fakeAutoloader {
+  class FakeAutoloader {
 
     /**
      * Registers this instance as an autoloader.