diff --git a/core/modules/block/lib/Drupal/block/Plugin/Core/Entity/Block.php b/core/modules/block/lib/Drupal/block/Plugin/Core/Entity/Block.php
index e8ccc63..0ff8ecc 100644
--- a/core/modules/block/lib/Drupal/block/Plugin/Core/Entity/Block.php
+++ b/core/modules/block/lib/Drupal/block/Plugin/Core/Entity/Block.php
@@ -74,9 +74,11 @@ class Block extends ConfigEntityBase {
   /**
    * The region this block is placed in.
    *
+   * The 'disabled' region is represented by -1.
+   *
    * @var string
    */
-  protected $region;
+  protected $region = -1;
 
   /**
    * Settings to control the block visibility.
@@ -135,6 +137,12 @@ class Block extends ConfigEntityBase {
    */
   public function getPlugin() {
     if (!$this->instance) {
+      // Throw an exception if no plugin string was provided.
+      if (!$this->plugin) {
+        throw new PluginException(format_string("The block '@block' did not specify a plugin.", array('@block' => $this->id())));
+      }
+
+      // Create an instance of the plugin and store its configuration.
       try {
         $this->instance = drupal_container()->get('plugin.manager.block')->createInstance($this->plugin, $this->configuration);
         $this->configuration += $this->instance->getConfig();
@@ -142,7 +150,7 @@ public function getPlugin() {
       catch (PluginException $e) {
         // Ignore blocks belonging to disabled modules, but re-throw valid
         // exceptions when the module is enabled and the plugin is misconfigured.
-        if (module_exists($this->module)) {
+        if (empty($this->module) || module_exists($this->module)) {
           throw $e;
         }
       }
diff --git a/core/modules/block/lib/Drupal/block/Tests/BlockStorageUnitTest.php b/core/modules/block/lib/Drupal/block/Tests/BlockStorageUnitTest.php
new file mode 100644
index 0000000..b1cc516
--- /dev/null
+++ b/core/modules/block/lib/Drupal/block/Tests/BlockStorageUnitTest.php
@@ -0,0 +1,208 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\block\Tests\BlockStorageUnitTest.
+ */
+
+namespace Drupal\block\Tests;
+
+use Drupal\simpletest\DrupalUnitTestBase;
+use Drupal\system\Plugin\block\block\SystemPoweredByBlock;
+use Drupal\Component\Plugin\Exception\PluginException;
+use Drupal\block\BlockStorageController;
+use Drupal\Core\Entity\EntityMalformedException;
+use Drupal\block\Plugin\Core\Entity\Block;
+
+/**
+ * Tests the storage of blocks.
+ *
+ * @see \Drupal\block\BlockStorageController
+ */
+class BlockStorageUnitTest extends DrupalUnitTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = array('system');
+
+  /**
+   * The block storage controller.
+   *
+   * @var \Drupal\block\BlockStorageController.
+   */
+  protected $controller;
+
+  public static function getInfo() {
+    return array(
+      'name' => 'Block storage',
+      'description' => 'Tests the storage of blocks.',
+      'group' => 'Block'
+    );
+  }
+
+  protected function setUp() {
+    parent::setUp();
+
+    $this->enableModules(array('block'));
+    $this->controller = entity_get_controller('block');
+  }
+
+  /**
+   * Tests CRUD operations.
+   */
+  public function testBlockCRUD() {
+    $this->assertTrue($this->controller instanceof BlockStorageController, 'The block storage controller is loaded.');
+
+    // Run each test method in the same installation.
+    $this->createTests();
+    $this->loadTests();
+    $this->renderTests();
+    $this->deleteTests();
+  }
+
+  /**
+   * Tests the creation of blocks.
+   */
+  protected function createTests() {
+    // Attempt to create a block without a plugin.
+    try {
+      $entity = $this->controller->create(array());
+      $this->fail('A block without a plugin was created with no exception thrown.');
+    }
+    catch (PluginException $e) {
+      $this->assertEqual('The block \'\' did not specify a plugin.', $e->getMessage(), 'An exception was thrown when a block was created without a plugin.');
+    }
+
+    // Create a block with only required values.
+    $entity = $this->controller->create(array(
+      'id' => 'stark.powered',
+      'plugin' => 'system_powered_by_block',
+    ));
+    $entity->save();
+
+    $this->assertTrue($entity instanceof Block, 'The newly created entity is a Block.');
+
+    // Verify all of the block properties.
+    $actual_properties = config('plugin.core.block.stark.powered')->get();
+    $this->assertTrue(!empty($actual_properties['uuid']), 'The block UUID is set.');
+    unset($actual_properties['uuid']);
+
+    // Ensure that default values are filled in.
+    $expected_properties = array(
+      'id' => 'stark.powered',
+      'label' => '',
+      'region' => '-1',
+      'weight' => '',
+      'cache' => '-1',
+      'module' => 'system',
+      'theme' => 'stark',
+      'status' => '1',
+      'visibility' => array(),
+      'plugin' => 'system_powered_by_block',
+      'configuration' => array(
+        'subject' => t('Powered by Drupal'),
+      ),
+    );
+    $this->assertIdentical($actual_properties, $expected_properties, 'The block properties are exported correctly.');
+
+    $this->assertTrue($entity->getPlugin() instanceof SystemPoweredByBlock, 'The entity has an instance of the correct block plugin.');
+  }
+
+  /**
+   * Tests the rendering of blocks.
+   */
+  protected function loadTests() {
+    $entities = $this->controller->load(array('stark.powered'));
+    $entity = reset($entities);
+
+    $this->assertTrue($entity instanceof Block, 'The loaded entity is a Block.');
+
+    // Verify several properties of the block.
+    $this->assertEqual($entity->get('region'), '-1');
+    $this->assertTrue($entity->get('status'));
+    $this->assertEqual($entity->get('theme'), 'stark');
+    $this->assertEqual($entity->get('module'), 'system');
+    $this->assertTrue($entity->uuid());
+  }
+
+  /**
+   * Tests the rendering of blocks.
+   */
+  protected function renderTests() {
+    $entity = $this->controller->create(array(
+      'id' => 'stark.powered',
+      'plugin' => 'system_powered_by_block',
+    ));
+
+    // Test the rendering of a block.
+    $output = entity_view($entity, 'block');
+    $expected = array();
+    $expected[] = '  <div id="block-powered"  class="block block-system">';
+    $expected[] = '';
+    $expected[] = '    <h2 class="">Powered by Drupal</h2>';
+    $expected[] = '  ';
+    $expected[] = '  <div class="content">';
+    $expected[] = '    <span>Powered by <a href="http://drupal.org">Drupal</a></span>  </div>';
+    $expected[] = '</div>';
+    $expected[] = '';
+    $expected_output = implode("\n", $expected);
+    $this->assertEqual(render($output), $expected_output, 'The block rendered correctly.');
+
+    // Reset the HTML IDs so that the next render is not affected.
+    drupal_static_reset('drupal_html_id');
+
+    // Test the rendering of a block with a given title.
+    $entity->set('label', 'Powered by Bananas');
+    $output = entity_view($entity, 'block');
+    $expected = array();
+    $expected[] = '  <div id="block-powered"  class="block block-system">';
+    $expected[] = '';
+    $expected[] = '    <h2 class="">Powered by Bananas</h2>';
+    $expected[] = '  ';
+    $expected[] = '  <div class="content">';
+    $expected[] = '    <span>Powered by <a href="http://drupal.org">Drupal</a></span>  </div>';
+    $expected[] = '</div>';
+    $expected[] = '';
+    $expected_output = implode("\n", $expected);
+    $this->assertEqual(render($output), $expected_output, 'The block rendered correctly.');
+  }
+
+  /**
+   * Tests the deleting of blocks.
+   */
+  protected function deleteTests() {
+    $entities = $this->controller->load(array('stark.powered'));
+    $entity = reset($entities);
+
+    // Ensure that the storage isn't currently empty.
+    $config_storage = $this->container->get('config.storage');
+    $config = $config_storage->listAll('plugin.core.block.');
+    $this->assertFalse(empty($config), 'There are blocks in config storage.');
+
+    // Delete the block.
+    $entity->delete();
+
+    // Ensure that the storage is now empty.
+    $config = $config_storage->listAll('plugin.core.block.');
+    $this->assertTrue(empty($config), 'There are no blocks in config storage.');
+  }
+
+  /**
+   * Tests the installation of default blocks.
+   */
+  public function testDefaultBlocks() {
+    $entities = $this->controller->load();
+    $this->assertTrue(empty($entities), 'There are no blocks initially.');
+
+    // Enable the Help module, which provides a default block.
+    $this->enableModules(array('help'));
+
+    $entities = $this->controller->load();
+    $entity = reset($entities);
+    $this->assertEqual($entity->id(), 'seven.help', 'The default help block was loaded.');
+  }
+
+}