diff --git a/core/modules/config/lib/Drupal/config/Tests/ConfigEntityUnitTest.php b/core/modules/config/lib/Drupal/config/Tests/ConfigEntityUnitTest.php
index 905ac98..14373a2 100644
--- a/core/modules/config/lib/Drupal/config/Tests/ConfigEntityUnitTest.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigEntityUnitTest.php
@@ -43,25 +43,27 @@ public function testStorageControllerMethods() {
 
   /**
    * Tests the behavior of creating conflicting entities.
+   *
+   * @todo Add tests for renaming and saving an existing config entity to
+   *   another existing ID.
    */
-  public function testCreatingConflictingEntities() {
+  public function testUniqueID() {
     // Create an entity with a label.
     $entity = entity_create('config_test', array('id' => 'foo', 'label' => 'Foo', 'style' => 'foo'));
     $entity->save();
 
     // Create an entity with the same ID, but a different label.
-    $exception = FALSE;
     try {
       $entity = entity_create('config_test', array('id' => 'foo', 'label' => 'Bananas'));
       $entity->save();
+      $this->fail('EntityMalformedException was thrown.');
     }
     catch (EntityMalformedException $e) {
-      $exception = TRUE;
+      $this->pass('EntityMalformedException was thrown.');
     }
     // Creating an entity with the same machine name should not succeed.
     $this->assertEqual($entity->label(), 'Foo', 'The entity label was not overwritten.');
     $this->assertEqual($entity->style, 'foo', 'The entity style was not overwritten.');
-    $this->assertTrue($exception, 'An exception was thrown when creating an entity with a duplicate ID.');
   }
 
 }
diff --git a/core/modules/config/lib/Drupal/config/Tests/ConfigImportTest.php b/core/modules/config/lib/Drupal/config/Tests/ConfigImportTest.php
index 4242bcc..95089f7 100644
--- a/core/modules/config/lib/Drupal/config/Tests/ConfigImportTest.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigImportTest.php
@@ -8,7 +8,6 @@
 namespace Drupal\config\Tests;
 
 use Drupal\simpletest\DrupalUnitTestBase;
-use Drupal\Core\Entity\EntityMalformedException;
 
 /**
  * Tests importing configuration from files into active configuration.
@@ -195,17 +194,4 @@ function testUpdated() {
     $this->assertFalse(config_sync_get_changes($staging, $storage));
   }
 
-  /**
-   * Tests enabling a module with a duplicate configuration entity.
-   */
-  function testDuplicate() {
-    $this->assertEqual(config('config_test.dynamic.default')->get('label'), 'Default', "Configuration object label is 'Default'.");
-    try {
-      module_enable(array('config_test_duplicate'));
-    }
-    catch (EntityMalformedException $e) {
-    }
-    $this->assertEqual(config('config_test.dynamic.default')->get('label'), 'Default', 'Configuration object is not silently overwritten on import.');
-  }
-
 }
diff --git a/core/modules/config/lib/Drupal/config/Tests/ConfigInstallTest.php b/core/modules/config/lib/Drupal/config/Tests/ConfigInstallTest.php
index b549119..e6e1409 100644
--- a/core/modules/config/lib/Drupal/config/Tests/ConfigInstallTest.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigInstallTest.php
@@ -8,6 +8,7 @@
 namespace Drupal\config\Tests;
 
 use Drupal\simpletest\DrupalUnitTestBase;
+use Drupal\Core\Entity\EntityMalformedException;
 
 /**
  * Tests installation of configuration objects in installation functionality.
@@ -64,4 +65,19 @@ function testModuleInstallation() {
     $this->assertFalse(isset($GLOBALS['hook_config_test']['predelete']));
     $this->assertFalse(isset($GLOBALS['hook_config_test']['delete']));
   }
+
+  /**
+   * Tests enabling a module with a duplicate configuration entity.
+   */
+  function testDuplicate() {
+    $this->enableModules(array('config_test'));
+    $this->assertEqual(config('config_test.dynamic.default')->get('label'), 'Default', "Configuration object label is 'Default'.");
+    try {
+      $this->enableModules(array('config_test_duplicate'));
+    }
+    catch (EntityMalformedException $e) {
+    }
+    $this->assertEqual(config('config_test.dynamic.default')->get('label'), 'Default', 'Configuration object is not silently overwritten on import.');
+  }
+
 }
diff --git a/core/modules/config/tests/config_test_duplicate/config/config_test.dynamic.default.yml b/core/modules/config/tests/config_test_duplicate/config/config_test.dynamic.default.yml
index 12efb31..deaa6b0 100644
--- a/core/modules/config/tests/config_test_duplicate/config/config_test.dynamic.default.yml
+++ b/core/modules/config/tests/config_test_duplicate/config/config_test.dynamic.default.yml
@@ -1,2 +1,4 @@
+# This purposefully duplicates config_test.dynamic.default.yml from
+# config_test.module, with different values.
 id: default
 label: Not default
diff --git a/core/modules/config/tests/config_test_duplicate/config_test_duplicate.info b/core/modules/config/tests/config_test_duplicate/config_test_duplicate.info
index 491708d..13e0c51 100644
--- a/core/modules/config/tests/config_test_duplicate/config_test_duplicate.info
+++ b/core/modules/config/tests/config_test_duplicate/config_test_duplicate.info
@@ -1,5 +1,5 @@
 name = Duplicate default configuration
-package = Core
+package = Testing
 version = VERSION
 core = 8.x
 hidden = TRUE