diff --git a/core/modules/simpletest/src/TestDiscovery.php b/core/modules/simpletest/src/TestDiscovery.php
index b9261a9..d44b015 100644
--- a/core/modules/simpletest/src/TestDiscovery.php
+++ b/core/modules/simpletest/src/TestDiscovery.php
@@ -321,8 +321,13 @@ public static function getTestInfo($classname, $doc_comment = NULL) {
       // Concrete tests must have a group.
       throw new MissingGroupException(sprintf('Missing @group annotation in %s', $classname));
     }
-    // Standardise the group name.
-    $info['group'] = Unicode::ucfirst($annotations['group']);
+    // Force all PHPUnit tests into the same group.
+    if (strpos($classname, 'Drupal\\Tests\\') === 0) {
+      $info['group'] = 'PHPUnit';
+    }
+    else {
+      $info['group'] = $annotations['group'];
+    }
 
     if (!empty($annotations['coversDefaultClass'])) {
       $info['description'] = 'Tests ' . $annotations['coversDefaultClass'] . '.';
diff --git a/core/modules/simpletest/tests/src/Unit/TestInfoParsingTest.php b/core/modules/simpletest/tests/src/Unit/TestInfoParsingTest.php
index 673a213..03a87b7 100644
--- a/core/modules/simpletest/tests/src/Unit/TestInfoParsingTest.php
+++ b/core/modules/simpletest/tests/src/Unit/TestInfoParsingTest.php
@@ -24,7 +24,7 @@ public function infoParserProvider() {
       // Expected result.
       [
         'name' => 'Drupal\Tests\simpletest\Unit\TestInfoParsingTest',
-        'group' => 'Simpletest',
+        'group' => 'PHPUnit',
         'description' => 'Tests \Drupal\simpletest\TestDiscovery.',
       ],
       // Classname.
@@ -35,7 +35,7 @@ public function infoParserProvider() {
       // Expected result.
       [
         'name' => 'Drupal\field\Tests\BulkDeleteTest',
-        'group' => 'Field',
+        'group' => 'field',
         'description' => 'Bulk delete storages and fields, and clean up afterwards.',
       ],
       // Classname.
@@ -63,7 +63,7 @@ public function infoParserProvider() {
       "/**
  * Bulk delete storages and fields, and clean up afterwards.
  *
- * @group test
+ * @group Test
  * @group field
  */
  ",
@@ -74,7 +74,7 @@ public function infoParserProvider() {
       // Expected result.
       [
         'name' => 'Drupal\field\Tests\BulkDeleteTest',
-        'group' => 'Field',
+        'group' => 'field',
         'description' => 'Bulk delete storages and fields, and clean up afterwards.',
         'requires' => ['module' => ['test']],
       ],
@@ -95,7 +95,7 @@ public function infoParserProvider() {
       // Expected result.
       [
         'name' => 'Drupal\field\Tests\BulkDeleteTest',
-        'group' => 'Field',
+        'group' => 'field',
         'description' => 'Bulk delete storages and fields, and clean up afterwards.',
         'requires' => ['module' => ['test', 'test1', 'test2']],
       ],
@@ -116,7 +116,7 @@ public function infoParserProvider() {
       // Expected result.
       [
         'name' => 'Drupal\field\Tests\BulkDeleteTest',
-        'group' => 'Field',
+        'group' => 'field',
         'description' => 'Bulk delete storages and fields, and clean up afterwards. And the summary line continues and there is no gap to the annotation.',
       ],
       // Classname.