diff --git a/core/includes/common.inc b/core/includes/common.inc
index 723d352..163a123 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -1874,6 +1874,7 @@ function drupal_pre_render_styles($elements) {
 
   $collection = &drupal_static('global_asset_collection', FALSE);
 
+  /** @var $collection \Drupal\Core\Asset\Collection\AssetCollectionInterface */
   $collection->resolveLibraries(\Drupal::service('asset.library_repository'));
   $collection->ksort();
 
diff --git a/core/lib/Drupal/Core/Asset/AssetLibraryRepository.php b/core/lib/Drupal/Core/Asset/AssetLibraryRepository.php
index 0744d3d..487d9e6 100644
--- a/core/lib/Drupal/Core/Asset/AssetLibraryRepository.php
+++ b/core/lib/Drupal/Core/Asset/AssetLibraryRepository.php
@@ -106,11 +106,14 @@ public function resolveDependencies(DependencyInterface $asset, $attach = TRUE)
         $dependencies[] = $library = $this->get($key);
 
         // Only bother attaching if operating on an asset.
-        if ($attach && $asset instanceof AssetInterface) {
+        if ($attach && $asset instanceof RelativePositionInterface) {
           foreach ($library as $libasset) {
-            if ($asset->getAssetType() === $libasset->getAssetType()) {
-              $asset->after($libasset);
+            if ($asset instanceof AssetInterface &&
+                $asset->getAssetType() !== $libasset->getAssetType()) {
+              continue;
             }
+
+            $asset->after($libasset);
           }
         }
       }
diff --git a/core/lib/Drupal/Core/Asset/BaseAsset.php b/core/lib/Drupal/Core/Asset/BaseAsset.php
index 0413a15..650417b 100644
--- a/core/lib/Drupal/Core/Asset/BaseAsset.php
+++ b/core/lib/Drupal/Core/Asset/BaseAsset.php
@@ -20,7 +20,7 @@
  * The methods load() and getLastModified() are left undefined, although a
  * reusable doLoad() method is available to child classes.
  */
-abstract class BaseAsset extends AsseticAdapterAsset implements AssetInterface, DependencyInterface {
+abstract class BaseAsset extends AsseticAdapterAsset implements AssetInterface, DependencyInterface, RelativePositionInterface {
 
   /**
    * @var AssetMetadataInterface
@@ -67,27 +67,21 @@ public function isPreprocessable() {
   /**
    * {@inheritdoc}
    */
-  public function hasDependencies() {
-    return !empty($this->dependencies);
-  }
-
-  /**
-   * {@inheritdoc}
-   */
   public function addDependency($key) {
-    if (!is_string($key)) {
+    if (!is_string($key) || substr_count($key, '/') !== 1) {
       throw new \InvalidArgumentException('Dependencies must be expressed as a string key identifying the depended-upon library.');
     }
 
     // The library key is stored as the key for cheap deduping.
     $this->dependencies[$key] = TRUE;
+    return $this;
   }
 
   /**
    * {@inheritdoc}
    */
-  public function clearDependencies() {
-    $this->dependencies = array();
+  public function hasDependencies() {
+    return !empty($this->dependencies);
   }
 
   /**
@@ -100,12 +94,9 @@ public function getDependencyInfo() {
   /**
    * {@inheritdoc}
    */
-  public function before($asset) {
-    if (!($asset instanceof AssetInterface || is_string($asset))) {
-      throw new \InvalidArgumentException('Ordering information must be declared using either an asset string id or the full AssetInterface object.');
-    }
-
-    $this->successors[] = $asset;
+  public function clearDependencies() {
+    $this->dependencies = array();
+    return $this;
   }
 
   /**
@@ -117,6 +108,14 @@ public function after($asset) {
     }
 
     $this->predecessors[] = $asset;
+    return $this;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function hasPredecessors() {
+    return !empty($this->predecessors);
   }
 
   /**
@@ -129,21 +128,44 @@ public function getPredecessors() {
   /**
    * {@inheritdoc}
    */
-  public function getSuccessors() {
-    return $this->successors;
+  public function clearPredecessors() {
+    $this->predecessors = array();
+    return $this;
   }
 
   /**
    * {@inheritdoc}
    */
-  public function clearSuccessors() {
-    $this->successors = array();
+  public function before($asset) {
+    if (!($asset instanceof AssetInterface || is_string($asset))) {
+      throw new \InvalidArgumentException('Ordering information must be declared using either an asset string id or the full AssetInterface object.');
+    }
+
+    $this->successors[] = $asset;
+    return $this;
   }
 
   /**
    * {@inheritdoc}
    */
-  public function clearPredecessors() {
-    $this->predecessors = array();
+  public function hasSuccessors() {
+    return !empty($this->successors);
   }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getSuccessors() {
+    return $this->successors;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function clearSuccessors() {
+    $this->successors = array();
+    return $this;
+  }
+
 }
+
diff --git a/core/lib/Drupal/Core/Asset/Collection/AssetCollection.php b/core/lib/Drupal/Core/Asset/Collection/AssetCollection.php
index 91e34eb..52a9f69 100644
--- a/core/lib/Drupal/Core/Asset/Collection/AssetCollection.php
+++ b/core/lib/Drupal/Core/Asset/Collection/AssetCollection.php
@@ -14,7 +14,6 @@
 use Drupal\Core\Asset\DependencyInterface;
 use Drupal\Core\Asset\Exception\FrozenObjectException;
 use Drupal\Core\Asset\Exception\UnsupportedAsseticBehaviorException;
-use Drupal\Core\Asset\RelativePositionInterface;
 
 /**
  * A container for assets.
@@ -90,6 +89,8 @@ public function replace($needle, AssetInterface $replacement, $graceful = FALSE)
    */
   public function freeze() {
     $this->frozen = TRUE;
+
+    return $this;
   }
 
   /**
@@ -129,6 +130,8 @@ public function getJs() {
   public function uksort($callback) {
     $this->attemptWrite(__METHOD__);
     uksort($this->assetIdMap, $callback);
+
+    return $this;
   }
 
   /**
@@ -137,6 +140,8 @@ public function uksort($callback) {
   public function ksort() {
     $this->attemptWrite(__METHOD__);
     ksort($this->assetIdMap);
+
+    return $this;
   }
 
   /**
@@ -147,6 +152,8 @@ public function ksort() {
   public function reverse() {
     $this->attemptWrite(__METHOD__);
     $this->assetIdMap = array_reverse($this->assetIdMap);
+
+    return $this;
   }
 
   /**
@@ -156,6 +163,8 @@ public function addUnresolvedLibrary($key) {
     $this->attemptWrite(__METHOD__);
     // The library key is stored as the key for cheap deduping.
     $this->libraries[$key] = TRUE;
+
+    return $this;
   }
 
   /**
@@ -178,6 +187,8 @@ public function getUnresolvedLibraries() {
   public function clearUnresolvedLibraries() {
     $this->attemptWrite(__METHOD__);
     $this->libraries = array();
+
+    return $this;
   }
 
   /**
@@ -211,6 +222,8 @@ public function resolveLibraries(AssetLibraryRepository $repository) {
         }
       }
     }
+
+    return $this;
   }
 
   /**
diff --git a/core/lib/Drupal/Core/Asset/Collection/AssetCollectionBasicInterface.php b/core/lib/Drupal/Core/Asset/Collection/AssetCollectionBasicInterface.php
index 9ae38fb..b1394cb 100644
--- a/core/lib/Drupal/Core/Asset/Collection/AssetCollectionBasicInterface.php
+++ b/core/lib/Drupal/Core/Asset/Collection/AssetCollectionBasicInterface.php
@@ -33,9 +33,8 @@
    *   The asset to add. Note that, despite the type requirements, it must
    *   conform to Drupal's AssetInterface.
    *
-   * @return bool
-   *   TRUE if the asset was added successfully, FALSE if it was already present
-   *   in the aggregate.
+   * @return AssetCollectionInterface
+   *   The current asset collection.
    *
    * @throws UnsupportedAsseticBehaviorException
    *   Thrown if a vanilla Assetic asset is provided.
diff --git a/core/lib/Drupal/Core/Asset/Collection/AssetCollectionInterface.php b/core/lib/Drupal/Core/Asset/Collection/AssetCollectionInterface.php
index 6649714..81d6f31 100644
--- a/core/lib/Drupal/Core/Asset/Collection/AssetCollectionInterface.php
+++ b/core/lib/Drupal/Core/Asset/Collection/AssetCollectionInterface.php
@@ -12,8 +12,6 @@
 /**
  * Describes an asset collection.
  *
- * TODO we need a few more methods here to deal with library resolution
- *
  * @see \Drupal\Core\Asset\Collection\AssetCollectionBasicInterface
  */
 interface AssetCollectionInterface extends AssetCollectionBasicInterface {
@@ -31,7 +29,8 @@
    * @param bool $freeze
    *   Whether to freeze the provided collection after merging. Defaults to TRUE.
    *
-   * @return void
+   * @return AssetCollectionInterface
+   *   The current asset collection.
    */
   public function mergeCollection(AssetCollectionInterface $collection, $freeze = TRUE);
 
@@ -43,7 +42,8 @@ public function mergeCollection(AssetCollectionInterface $collection, $freeze =
    *
    * TODO put this on the basic interface so aggregates have it, too?
    *
-   * @return void
+   * @return AssetCollectionInterface
+   *   The current asset collection.
    */
   public function freeze();
 
@@ -73,21 +73,24 @@ public function getJs();
    *
    * @param $callback
    *
-   * @return void
+   * @return AssetCollectionInterface
+   *   The current asset collection.
    */
   public function uksort($callback);
 
   /**
    * Sorts contained assets via ksort() on their ids.
    *
-   * @return void
+   * @return AssetCollectionInterface
+   *   The current asset collection.
    */
   public function ksort();
 
   /**
    * Reverses the sort order of the contained assets.
    *
-   * @return void
+   * @return AssetCollectionInterface
+   *   The current asset collection.
    */
   public function reverse();
 
@@ -102,7 +105,8 @@ public function reverse();
    *   slash-delimited, with the first part being the module owner and the
    *   second part being the library name.
    *
-   * @return void
+   * @return AssetCollectionInterface
+   *   The current asset collection.
    *
    * @see AssetCollectionInterface::resolveLibraries()
    */
@@ -127,7 +131,8 @@ public function getUnresolvedLibraries();
   /**
    * Empties the collection of its unresolved library keys.
    *
-   * @return void
+   * @return AssetCollectionInterface
+   *   The current asset collection.
    */
   public function clearUnresolvedLibraries();
 
@@ -142,7 +147,8 @@ public function clearUnresolvedLibraries();
    *   The AssetLibraryRepository to use for resolving library keys into
    *   AssetLibrary objects.
    *
-   * @return void
+   * @return AssetCollectionInterface
+   *   The current asset collection.
    */
   public function resolveLibraries(AssetLibraryRepository $repository);
 }
diff --git a/core/lib/Drupal/Core/Asset/Collection/AssetLibrary.php b/core/lib/Drupal/Core/Asset/Collection/AssetLibrary.php
index 6c6ad54..4e807bd 100644
--- a/core/lib/Drupal/Core/Asset/Collection/AssetLibrary.php
+++ b/core/lib/Drupal/Core/Asset/Collection/AssetLibrary.php
@@ -7,11 +7,19 @@
 
 namespace Drupal\Core\Asset\Collection;
 
+use Drupal\Core\Asset\AssetInterface;
 use Drupal\Core\Asset\DependencyInterface;
 use Drupal\Core\Asset\Collection\AssetCollection;
 use Drupal\Core\Asset\Exception\FrozenObjectException;
+use Drupal\Core\Asset\RelativePositionInterface;
 
-class AssetLibrary extends AssetCollection implements DependencyInterface {
+/**
+ * An asset library is a named collection of assets.
+ *
+ * The primary role of an asset library is to be declared as a dependency by
+ * other assets (including assets declared by other libraries).
+ */
+class AssetLibrary extends AssetCollection implements DependencyInterface, RelativePositionInterface {
 
   /**
    * The asset library's title.
@@ -123,29 +131,22 @@ public function getVersion() {
   /**
    * {@inheritdoc}
    */
-  public function hasDependencies() {
-    return !empty($this->dependencies);
-  }
-
-  /**
-   * {@inheritdoc}
-   */
   public function addDependency($key) {
     $this->attemptWrite(__METHOD__);
-    if (!is_string($key)) {
+    if (!is_string($key) || substr_count($key, '/') !== 1) {
       throw new \InvalidArgumentException('Dependencies must be expressed as a string key identifying the depended-upon library.');
     }
 
     // The library key is stored as the key for cheap deduping.
     $this->dependencies[$key] = TRUE;
+    return $this;
   }
 
   /**
    * {@inheritdoc}
    */
-  public function clearDependencies() {
-    $this->attemptWrite(__METHOD__);
-    $this->dependencies = array();
+  public function hasDependencies() {
+    return !empty($this->dependencies);
   }
 
   /**
@@ -158,15 +159,30 @@ public function getDependencyInfo() {
   /**
    * {@inheritdoc}
    */
-  public function before($asset) {
-    $this->successors[] = $asset;
+  public function clearDependencies() {
+    $this->attemptWrite(__METHOD__);
+    $this->dependencies = array();
+    return $this;
   }
 
   /**
    * {@inheritdoc}
    */
   public function after($asset) {
+    $this->attemptWrite(__METHOD__);
+    if (!($asset instanceof AssetInterface || is_string($asset))) {
+      throw new \InvalidArgumentException('Ordering information must be declared using either an asset string id or the full AssetInterface object.');
+    }
+
     $this->predecessors[] = $asset;
+    return $this;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function hasPredecessors() {
+    return !empty($this->predecessors);
   }
 
   /**
@@ -179,22 +195,46 @@ public function getPredecessors() {
   /**
    * {@inheritdoc}
    */
-  public function getSuccessors() {
-    return $this->successors;
+  public function clearPredecessors() {
+    $this->attemptWrite(__METHOD__);
+    $this->predecessors = array();
+    return $this;
   }
 
   /**
    * {@inheritdoc}
    */
-  public function clearSuccessors() {
-    $this->successors = array();
+  public function before($asset) {
+    $this->attemptWrite(__METHOD__);
+    if (!($asset instanceof AssetInterface || is_string($asset))) {
+      throw new \InvalidArgumentException('Ordering information must be declared using either an asset string id or the full AssetInterface object.');
+    }
+
+    $this->successors[] = $asset;
+    return $this;
   }
 
   /**
    * {@inheritdoc}
    */
-  public function clearPredecessors() {
-    $this->predecessors = array();
+  public function hasSuccessors() {
+    return !empty($this->successors);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getSuccessors() {
+    return $this->successors;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function clearSuccessors() {
+    $this->attemptWrite(__METHOD__);
+    $this->successors = array();
+    return $this;
   }
 
   /**
diff --git a/core/lib/Drupal/Core/Asset/Collection/BasicAssetCollection.php b/core/lib/Drupal/Core/Asset/Collection/BasicAssetCollection.php
index 2cd2f16..85ce488 100644
--- a/core/lib/Drupal/Core/Asset/Collection/BasicAssetCollection.php
+++ b/core/lib/Drupal/Core/Asset/Collection/BasicAssetCollection.php
@@ -68,18 +68,16 @@ public function add(AsseticAssetInterface $asset) {
     }
     $this->ensureCorrectType($asset);
 
-    if ($this->contains($asset) || $this->find($asset->id())) {
-      return FALSE;
-    }
+    if (!($this->contains($asset) || $this->find($asset->id()))) {
+      $this->assetStorage->attach($asset);
+      $this->assetIdMap[$asset->id()] = $asset;
 
-    $this->assetStorage->attach($asset);
-    $this->assetIdMap[$asset->id()] = $asset;
-
-    if ($asset instanceof AssetCollectionBasicInterface) {
-      $this->nestedStorage->attach($asset);
+      if ($asset instanceof AssetCollectionBasicInterface) {
+        $this->nestedStorage->attach($asset);
+      }
     }
 
-    return TRUE;
+    return $this;
   }
 
   /**
diff --git a/core/lib/Drupal/Core/Asset/DependencyInterface.php b/core/lib/Drupal/Core/Asset/DependencyInterface.php
index cea6ceb..00488b3 100644
--- a/core/lib/Drupal/Core/Asset/DependencyInterface.php
+++ b/core/lib/Drupal/Core/Asset/DependencyInterface.php
@@ -8,17 +8,13 @@
 
 /**
  * Describes assets that can declare dependencies on asset libraries.
- *
- * "Dependency" expands the concept of positioning expressed by the parent
- * interface RelativePositionInterface by ensuring the presence of another
- * another asset.
  */
-interface DependencyInterface extends RelativePositionInterface {
+interface DependencyInterface {
 
   /**
    * Indicates whether this asset has one or more library dependencies.
    *
-   * @return boolean
+   * @return bool
    */
   public function hasDependencies();
 
@@ -37,8 +33,9 @@ public function getDependencyInfo();
    *   The string identifying the library. It should be two-part composite key,
    *   slash-delimited, with the first part being the module owner and the
    *   second part being the library name.
-
-   * @return void
+   *
+   * @return DependencyInterface
+   *   The current DependencyInterface object.
    */
   public function addDependency($key);
 
@@ -47,8 +44,9 @@ public function addDependency($key);
    *
    * This does not affect ordering data.
    *
-   * @return void
+   * @return DependencyInterface
+   *   The current DependencyInterface object.
    */
   public function clearDependencies();
-
 }
+
diff --git a/core/lib/Drupal/Core/Asset/Factory/AssetCollectorInterface.php b/core/lib/Drupal/Core/Asset/Factory/AssetCollectorInterface.php
index 0a59ec2..f171de1 100644
--- a/core/lib/Drupal/Core/Asset/Factory/AssetCollectorInterface.php
+++ b/core/lib/Drupal/Core/Asset/Factory/AssetCollectorInterface.php
@@ -72,6 +72,7 @@ public function add(AssetInterface $asset);
    * @see clearLastCss().
    *
    * @return \Drupal\Core\Asset\AssetInterface
+   *   The created AssetInterface object.
    *
    * @throws \InvalidArgumentException
    *   Thrown if an invalid asset type or source type is passed.
@@ -91,8 +92,8 @@ public function create($asset_type, $source_type, $data, $options = array(), $fi
    * end of such a contiguous series is reached, or by the asset creator
    * themselves if they want to avoid the creation of the ordering relationship.
    *
-   * @return AssetCollector
-   *   The current AssetCollector instance, for easy chaining.
+   * @return AssetCollectorInterface
+   *   The current asset collector.
    */
   public function clearLastCss();
 
@@ -103,8 +104,10 @@ public function clearLastCss();
    * all assets generated via its create() method to the collection.
    *
    * @param AssetCollectionInterface $collection
+   *   The collection the collector should use internally.
    *
-   * @return void
+   * @return AssetCollectorInterface
+   *   The current asset collector.
    *
    * @throws LockedObjectException
    *   Thrown if the collector is locked when this method is called.
@@ -114,7 +117,8 @@ public function setCollection(AssetCollectionInterface $collection);
   /**
    * Clears the internal collection for this collector.
    *
-   * @return void
+   * @return AssetCollectorInterface
+   *   The current asset collector.
    *
    * @throws LockedObjectException
    *   Thrown if the collector is locked when this method is called.
@@ -138,7 +142,8 @@ public function hasCollection();
    * @param mixed $key
    *   The key used to lock the collector.
    *
-   * @return void
+   * @return AssetCollectorInterface
+   *   The current asset collector.
    *
    * @throws LockedObjectException
    *   Thrown if the collector is already locked.
@@ -153,7 +158,8 @@ public function lock($key);
    * @param mixed $key
    *   The key with which to unlock the collector.
    *
-   * @return void
+   * @return AssetCollectorInterface
+   *   The current asset collector.
    *
    * @throws LockedObjectException
    *   Thrown if the incorrect key is provided, or if the collector is not
@@ -174,7 +180,8 @@ public function isLocked();
    * @param MetadataFactoryInterface $factory
    *   The factory to use.
    *
-   * @return void
+   * @return AssetCollectorInterface
+   *   The current asset collector.
    *
    * @throws LockedObjectException
    *   Thrown if the collector is locked when this method is called.
diff --git a/core/lib/Drupal/Core/Asset/RelativePositionInterface.php b/core/lib/Drupal/Core/Asset/RelativePositionInterface.php
index 66293d8..cd6c6e0 100644
--- a/core/lib/Drupal/Core/Asset/RelativePositionInterface.php
+++ b/core/lib/Drupal/Core/Asset/RelativePositionInterface.php
@@ -10,14 +10,27 @@
  * Describes an asset or asset-like object that can declare dependencies.
  */
 interface RelativePositionInterface {
+
   /**
-   * Clears (removes) all ordering info declared by after() for this asset.
+   * Declare that an asset should, if present, precede this asset on output.
    *
-   * This does not affect dependency data.
+   * Either the string identifier for the other asset, or the asset object
+   * itself, should be provided.
    *
-   * @return void
+   * @param string|AssetInterface $asset
+   *   The asset to precede the current asset.
+   *
+   * @return RelativePositionInterface
+   *   The current RelativePositionInterface object.
    */
-  public function clearPredecessors();
+  public function after($asset);
+
+  /**
+   * Indicates whether this asset has one or more asset predecessors.
+   *
+   * @return bool
+   */
+  public function hasPredecessors();
 
   /**
    * Returns ordering info declared by after().
@@ -29,6 +42,16 @@ public function clearPredecessors();
   public function getPredecessors();
 
   /**
+   * Clears all ordering info declared by after() for this asset.
+   *
+   * This does not affect dependency data.
+   *
+   * @return RelativePositionInterface
+   *   The current RelativePositionInterface object.
+   */
+  public function clearPredecessors();
+
+  /**
    * Declare that an asset should, if present, succeed this asset on output.
    *
    * Either the string identifier for the other asset, or the asset object
@@ -37,11 +60,19 @@ public function getPredecessors();
    * @param string|AssetInterface $asset
    *   The asset to succeed the current asset.
    *
-   * @return void
+   * @return RelativePositionInterface
+   *   The current RelativePositionInterface object.
    */
   public function before($asset);
 
   /**
+   * Indicates whether this asset has one or more asset successors.
+   *
+   * @return bool
+   */
+  public function hasSuccessors();
+
+  /**
    * Returns ordering info declared by before().
    *
    * @return array
@@ -55,20 +86,10 @@ public function getSuccessors();
    *
    * This does not affect dependency data.
    *
-   * @return void
+   * @return RelativePositionInterface
+   *   The current RelativePositionInterface object.
    */
   public function clearSuccessors();
 
-  /**
-   * Declare that an asset should, if present, precede this asset on output.
-   *
-   * Either the string identifier for the other asset, or the asset object
-   * itself, should be provided.
-   *
-   * @param string|AssetInterface $asset
-   *   The asset to precede the current asset.
-   *
-   * @return void
-   */
-  public function after($asset);
-}
\ No newline at end of file
+}
+
diff --git a/core/tests/Drupal/Tests/Core/Asset/Aggregate/AssetAggregateTest.php b/core/tests/Drupal/Tests/Core/Asset/Aggregate/AssetAggregateTest.php
index e6a90a7..326a9cc 100644
--- a/core/tests/Drupal/Tests/Core/Asset/Aggregate/AssetAggregateTest.php
+++ b/core/tests/Drupal/Tests/Core/Asset/Aggregate/AssetAggregateTest.php
@@ -10,13 +10,14 @@
 use Drupal\Core\Asset\Collection\AssetCollectionBasicInterface;
 use Drupal\Core\Asset\Exception\AssetTypeMismatchException;
 use Drupal\Core\Asset\Exception\UnsupportedAsseticBehaviorException;
+use Drupal\Tests\Core\Asset\AssetUnitTest;
 use Drupal\Tests\Core\Asset\Collection\BasicAssetCollectionTest;
 
 /**
  * @coversDefaultClass \Drupal\Core\Asset\Aggregate\AssetAggregate
  * @group Asset
  */
-class AssetAggregateTest extends BasicAssetCollectionTest {
+class AssetAggregateTest extends AssetUnitTest {
 
   public static function getInfo() {
     return array(
@@ -81,7 +82,7 @@ public function testGetMetadata() {
   public function testAdd() {
     $aggregate = $this->getAggregate();
     $asset = $this->createStubFileAsset();
-    $this->assertTrue($aggregate->add($asset));
+    $this->assertSame($aggregate, $aggregate->add($asset));
 
     $this->assertAttributeContains($asset, 'assetStorage', $aggregate);
     $this->assertAttributeContains($asset, 'assetIdMap', $aggregate);
diff --git a/core/tests/Drupal/Tests/Core/Asset/AssetLibraryRepositoryTest.php b/core/tests/Drupal/Tests/Core/Asset/AssetLibraryRepositoryTest.php
index 44510f8..adfe81e 100644
--- a/core/tests/Drupal/Tests/Core/Asset/AssetLibraryRepositoryTest.php
+++ b/core/tests/Drupal/Tests/Core/Asset/AssetLibraryRepositoryTest.php
@@ -186,6 +186,7 @@ public function testResolveDependencies() {
 
     $compatible_dep = $this->createStubFileAsset();
     $incompatible_dep = $this->createStubFileAsset('js');
+    $lib_dep = $this->createStubFileAsset();
 
     $main_asset = $this->getMock('Drupal\\Core\\Asset\\FileAsset', array(), array(), '', FALSE);
     $main_asset->expects($this->exactly(2))
@@ -207,6 +208,8 @@ public function testResolveDependencies() {
     $library1->expects($this->once())
       ->method('getDependencyInfo')
       ->will($this->returnValue(array('foo/baz', 'qux/bing')));
+    $library1->expects($this->once())
+      ->method('after')->with($lib_dep);
 
     $it = new \ArrayIterator(array($compatible_dep, $incompatible_dep));
 
@@ -215,9 +218,18 @@ public function testResolveDependencies() {
       ->will($this->returnValue($it));
 
     $library2 = $this->getMock('Drupal\\Core\\Asset\\Collection\\AssetLibrary');
+    $library2->expects($this->once())
+      ->method('getIterator')
+      ->will($this->returnValue(new \ArrayIterator(array())));
+    $library2->expects($this->never())
+      ->method('hasDependencies');
+
     $library3 = $this->getMock('Drupal\\Core\\Asset\\Collection\\AssetLibrary');
+    $library3->expects($this->once())
+      ->method('getIterator')
+      ->will($this->returnValue(new \ArrayIterator(array($lib_dep))));
     $library3->expects($this->never())
-      ->method('getDependencyInfo')
+      ->method('hasDependencies')
       ->will($this->returnValue(array('qux/quark')));
 
     $library4 = $this->getMock('Drupal\\Core\\Asset\\Collection\\AssetLibrary');
diff --git a/core/tests/Drupal/Tests/Core/Asset/BaseAssetTest.php b/core/tests/Drupal/Tests/Core/Asset/BaseAssetTest.php
index 475d0e9..7a3125f 100644
--- a/core/tests/Drupal/Tests/Core/Asset/BaseAssetTest.php
+++ b/core/tests/Drupal/Tests/Core/Asset/BaseAssetTest.php
@@ -9,7 +9,7 @@
 use Drupal\Core\Asset\BaseAsset;
 
 /**
- *
+ * @coversDefaultClass \Drupal\Core\Asset\BaseAsset
  * @group Asset
  */
 class BaseAssetTest extends AssetUnitTest {
@@ -63,19 +63,15 @@ public function testIsPreprocessable() {
   }
 
   /**
-   * Tests all dependency-related methods.
+   * @covers ::addDependency
    */
-  public function testDependencies() {
+  public function testAddDependency() {
     $asset = $this->createBaseAsset();
 
-    $asset->addDependency('foo/bar');
-    $this->assertEquals(array('foo/bar'), $asset->getDependencyInfo());
-    $this->assertTrue($asset->hasDependencies());
+    $this->assertSame($asset, $asset->addDependency('foo/bar'));
+    $this->assertAttributeContains('foo/bar', 'dependencies', $asset);
 
-    $asset->clearDependencies();
-    $this->assertEmpty($asset->getDependencyInfo());
-
-    $invalid = array(0, 1.1, fopen(__FILE__, 'r'), TRUE, array(), new \stdClass);
+    $invalid = array('foo', 'foo//bar', 0, 1.1, fopen(__FILE__, 'r'), TRUE, array(), new \stdClass);
 
     try {
       foreach ($invalid as $val) {
@@ -85,39 +81,114 @@ public function testDependencies() {
     } catch (\InvalidArgumentException $e) {}
   }
 
-  public function testSuccessors() {
+  /**
+   * @depends testAddDependency
+   * @covers ::hasDependencies
+   */
+  public function testHasDependencies() {
     $asset = $this->createBaseAsset();
-    $dep = $this->createBaseAsset();
+    $this->assertFalse($asset->hasDependencies());
 
-    $asset->before('foo');
-    $asset->before($dep);
+    $asset->addDependency('foo/bar');
+    $this->assertTrue($asset->hasDependencies());
+  }
 
-    $this->assertEquals(array('foo', $dep), $asset->getSuccessors());
+  /**
+   * @depends testAddDependency
+   * @covers ::getDependencyInfo
+   */
+  public function testGetDependencyInfo() {
+    $asset = $this->createBaseAsset();
+    $this->assertEmpty($asset->getDependencyInfo());
 
-    $asset->clearSuccessors();
-    $this->assertEmpty($asset->getSuccessors());
+    $asset->addDependency('foo/bar');
+    $this->assertEquals(array('foo/bar'), $asset->getDependencyInfo());
+  }
+
+  /**
+   * @depends testAddDependency
+   * @depends testHasDependencies
+   * @covers ::clearDependencies
+   */
+  public function testClearDependencies() {
+    $asset = $this->createBaseAsset();
+    $asset->addDependency('foo/bar');
+
+    $this->assertSame($asset, $asset->clearDependencies());
+    $this->assertFalse($asset->hasDependencies());
+  }
+
+  /**
+   * @covers ::after
+   */
+  public function testAfter() {
+    $asset = $this->createBaseAsset();
+    $dep = $this->createBaseAsset();
+
+    $this->assertSame($asset, $asset->after('foo'));
+    $this->assertSame($asset, $asset->after($dep));
+
+    $this->assertAttributeContains($dep, 'predecessors', $asset);
 
     $invalid = array(0, 1.1, fopen(__FILE__, 'r'), TRUE, array(), new \stdClass);
 
     try {
       foreach ($invalid as $val) {
-        $asset->before($val);
+        $asset->after($val);
         $this->fail('Was able to create an ordering relationship with an inappropriate value.');
       }
     } catch (\InvalidArgumentException $e) {}
   }
 
-  public function testPredecessors() {
+  /**
+   * @depends testAfter
+   * @covers ::hasPredecessors
+   */
+  public function testHasPredecessors() {
     $asset = $this->createBaseAsset();
-    $dep = $this->createBaseAsset();
+    $this->assertFalse($asset->hasPredecessors());
 
     $asset->after('foo');
-    $asset->after($dep);
-    $this->assertEquals(array('foo', $dep), $asset->getPredecessors());
+    $this->assertTrue($asset->hasPredecessors());
+  }
 
-    $asset->clearPredecessors();
+  /**
+   * @depends testAfter
+   * @covers ::getPredecessors
+   */
+  public function testGetPredecessors() {
+    $asset = $this->createBaseAsset();
     $this->assertEmpty($asset->getPredecessors());
 
+    $asset->after('foo');
+    $this->assertEquals(array('foo'), $asset->getPredecessors());
+  }
+
+  /**
+   * @depends testAfter
+   * @depends testHasPredecessors
+   * @covers ::clearPredecessors
+   */
+  public function testClearPredecessors() {
+    $asset = $this->createBaseAsset();
+    $asset->after('foo');
+
+    $this->assertSame($asset, $asset->clearPredecessors());
+    $this->assertFalse($asset->hasPredecessors());
+  }
+
+  /**
+   * @covers ::before
+   */
+  public function testBefore() {
+    $asset = $this->createBaseAsset();
+    $dep = $this->createBaseAsset();
+
+    $this->assertSame($asset, $asset->before('foo'));
+    $this->assertSame($asset, $asset->before($dep));
+
+    $this->assertAttributeContains($dep, 'successors', $asset);
+
     $invalid = array(0, 1.1, fopen(__FILE__, 'r'), TRUE, array(), new \stdClass);
 
     try {
@@ -128,6 +199,42 @@ public function testPredecessors() {
     } catch (\InvalidArgumentException $e) {}
   }
 
+  /**
+   * @depends testBefore
+   * @covers ::hasSuccessors
+   */
+  public function testHasSuccessors() {
+    $asset = $this->createBaseAsset();
+    $this->assertFalse($asset->hasSuccessors());
+
+    $asset->before('foo');
+    $this->assertTrue($asset->hasSuccessors());
+  }
+
+  /**
+   * @depends testBefore
+   * @covers ::getSuccessors
+   */
+  public function testGetSuccessors() {
+    $asset = $this->createBaseAsset();
+    $this->assertEmpty($asset->getSuccessors());
+
+    $asset->before('foo');
+    $this->assertEquals(array('foo'), $asset->getSuccessors());
+  }
+
+   /**
+   * @depends testBefore
+   * @covers ::clearSuccessors
+   */
+  public function testClearSuccessors() {
+    $asset = $this->createBaseAsset();
+    $asset->before('foo');
+
+    $this->assertSame($asset, $asset->clearSuccessors());
+    $this->assertFalse($asset->hasSuccessors());
+  }
+
   public function testClone() {
     $mockmeta = $this->createStubAssetMetadata();
     $asset = $this->getMockForAbstractClass('\\Drupal\\Core\\Asset\\BaseAsset', array($mockmeta));
diff --git a/core/tests/Drupal/Tests/Core/Asset/Collection/AssetCollectionTest.php b/core/tests/Drupal/Tests/Core/Asset/Collection/AssetCollectionTest.php
index cad02c3..4c4357a 100644
--- a/core/tests/Drupal/Tests/Core/Asset/Collection/AssetCollectionTest.php
+++ b/core/tests/Drupal/Tests/Core/Asset/Collection/AssetCollectionTest.php
@@ -4,18 +4,18 @@
  * Contains Drupal\Tests\Core\Asset\AssetCollectionTest.
  */
 
-
 namespace Drupal\Tests\Core\Asset\Collection;
 
 use Drupal\Core\Asset\Collection\AssetCollection;
 use Drupal\Core\Asset\Collection\AssetCollectionBasicInterface;
 use Drupal\Core\Asset\Exception\FrozenObjectException;
+use Drupal\Tests\Core\Asset\AssetUnitTest;
 
 /**
  * @coversDefaultClass \Drupal\Core\Asset\Collection\AssetCollection
  * @group Asset
  */
-class AssetCollectionTest extends BasicAssetCollectionTest {
+class AssetCollectionTest extends AssetUnitTest {
 
   /**
    * @var AssetCollection
@@ -50,37 +50,15 @@ public function testAdd() {
     $asset1 = $this->createStubFileAsset();
     $asset2 = $this->createStubFileAsset();
 
-    $this->assertTrue($this->collection->add($asset1));
-    $this->assertTrue($this->collection->add($asset2));
+    // test fluency
+    $this->assertSame($this->collection, $this->collection->add($asset1));
+    $this->assertSame($this->collection, $this->collection->add($asset2));
 
     $this->assertContains($asset1, $this->collection);
     $this->assertContains($asset2, $this->collection);
   }
 
   /**
-   * Tests that adding the same asset twice is disallowed.
-   *
-   * @depends testAdd
-   * @covers ::add
-   */
-  public function testDoubleAdd() {
-    $asset = $this->createStubFileAsset();
-    $this->assertTrue($this->collection->add($asset));
-
-    $this->assertTrue($this->collection->contains($asset));
-
-    // Test by object identity
-    $this->assertFalse($this->collection->add($asset));
-    // Test by id
-    $asset2 = $this->getMock('Drupal\\Core\\Asset\\FileAsset', array(), array(), '', FALSE);
-    $asset2->expects($this->once())
-      ->method('id')
-      ->will($this->returnValue($asset->id()));
-
-    $this->assertFalse($this->collection->add($asset2));
-  }
-
-  /**
    * @depends testAdd
    * @covers ::contains
    */
@@ -185,6 +163,7 @@ public function testRemoveById() {
 
   /**
    * @expectedException \OutOfBoundsException
+   * @covers ::remove
    */
   public function testRemoveNonexistentId() {
     $this->assertFalse($this->collection->remove('foo', TRUE));
@@ -193,6 +172,7 @@ public function testRemoveNonexistentId() {
 
   /**
    * @expectedException \OutOfBoundsException
+   * @covers ::remove
    */
   public function testRemoveNonexistentAsset() {
     $stub = $this->createStubFileAsset();
@@ -210,7 +190,7 @@ public function testMergeCollection() {
     $stub2 = $this->createStubFileAsset();
 
     $coll2->add($stub1);
-    $this->collection->mergeCollection($coll2);
+    $this->assertSame($this->collection, $this->collection->mergeCollection($coll2));
 
     $this->assertContains($stub1, $this->collection);
     $this->assertTrue($coll2->isFrozen());
@@ -219,7 +199,7 @@ public function testMergeCollection() {
     $coll3->add($stub1);
     $coll3->add($stub2);
     // Ensure no duplicates, and don't freeze merged bag
-    $this->collection->mergeCollection($coll3, FALSE);
+    $this->assertSame($this->collection, $this->collection->mergeCollection($coll3, FALSE));
 
     $contained = array(
       $stub1->id() => $stub1,
@@ -232,6 +212,10 @@ public function testMergeCollection() {
   /**
    * Tests that all methods that should be disabled by freezing the collection
    * correctly trigger an exception.
+   *
+   * @covers ::freeze
+   * @covers ::isFrozen
+   * @covers ::attemptWrite
    */
   public function testExceptionOnWriteWhenFrozen() {
     $stub = $this->createStubFileAsset();
@@ -248,6 +232,10 @@ public function testExceptionOnWriteWhenFrozen() {
       'resolveLibraries' => array($this->getMock('Drupal\\Core\\Asset\\AssetLibraryRepository', array(), array(), '', FALSE)),
     );
 
+    // No exception before freeze
+    list($method, $args) = each($write_protected);
+    call_user_func_array(array($this->collection, $method), $args);
+
     $this->collection->freeze();
     foreach ($write_protected as $method => $args) {
       try {
@@ -262,7 +250,7 @@ public function testExceptionOnWriteWhenFrozen() {
    * @covers ::find
    * @expectedException OutOfBoundsException
    */
-  public function testGetById() {
+  public function testFind() {
     $metamock = $this->createStubAssetMetadata();
 
     $asset = $this->getMock('\\Drupal\\Core\\Asset\\FileAsset', array(), array($metamock, 'foo'));
@@ -303,7 +291,7 @@ public function testUkSort() {
       return strnatcasecmp($a, $b);
     };
 
-    $this->collection->uksort($dummysort);
+    $this->assertSame($this->collection, $this->collection->uksort($dummysort));
     uksort($assets, $dummysort);
     $this->assertEquals($assets, $this->collection->all());
   }
@@ -327,7 +315,7 @@ public function testKsort() {
       $stub3->id() => $stub3,
     );
 
-    $this->collection->ksort();
+    $this->assertSame($this->collection, $this->collection->ksort());
     ksort($assets);
     $this->assertEquals($assets, $this->collection->all());
   }
@@ -351,7 +339,7 @@ public function testReverse() {
       $stub1->id() => $stub1,
     );
 
-    $this->collection->reverse();
+    $this->assertSame($this->collection, $this->collection->reverse());
     $this->assertEquals($assets, $this->collection->all());
   }
 
@@ -359,7 +347,7 @@ public function testReverse() {
    * @covers ::addUnresolvedLibrary
    */
   public function testAddUnresolvedLibrary() {
-    $this->collection->addUnresolvedLibrary('foo/bar');
+    $this->assertSame($this->collection, $this->collection->addUnresolvedLibrary('foo/bar'));
 
     $this->assertAttributeContains('foo/bar', 'libraries', $this->collection);
   }
@@ -383,7 +371,7 @@ public function testHasUnresolvedLibraries() {
    */
   public function testClearUnresolvedLibraries() {
     $this->collection->addUnresolvedLibrary('foo/bar');
-    $this->collection->clearUnresolvedLibraries();
+    $this->assertSame($this->collection, $this->collection->clearUnresolvedLibraries());
 
     $this->assertFalse($this->collection->hasUnresolvedLibraries());
   }
@@ -505,7 +493,7 @@ public function testResolveLibrariesAgain() {
       ->will($this->returnValue(array()));
 
     $this->collection->add($coll_asset);
-    $this->collection->resolveLibraries($repository);
+    $this->assertSame($this->collection, $this->collection->resolveLibraries($repository));
 
     $expected = array(
       $coll_asset->id() => $coll_asset,
diff --git a/core/tests/Drupal/Tests/Core/Asset/Collection/AssetLibraryTest.php b/core/tests/Drupal/Tests/Core/Asset/Collection/AssetLibraryTest.php
index d70ef5b..bf94ea3 100644
--- a/core/tests/Drupal/Tests/Core/Asset/Collection/AssetLibraryTest.php
+++ b/core/tests/Drupal/Tests/Core/Asset/Collection/AssetLibraryTest.php
@@ -7,10 +7,11 @@
 namespace Drupal\Tests\Core\Asset\Collection;
 
 use Drupal\Core\Asset\Collection\AssetLibrary;
+use Drupal\Core\Asset\Exception\FrozenObjectException;
 use Drupal\Tests\Core\Asset\AssetUnitTest;
 
 /**
- *
+ * @coversDefaultClass \Drupal\Core\Asset\Collection\AssetLibrary
  * @group Asset
  */
 class AssetLibraryTest extends AssetUnitTest {
@@ -27,54 +28,233 @@ public function getLibraryFixture() {
     $library = new AssetLibrary();
     $library->setTitle('foo')
       ->setVersion('1.2.3')
-      ->setWebsite('http://foo.bar')
-      ->addDependency('foo/bar');
+      ->setWebsite('http://foo.bar');
     return $library;
   }
 
+  /**
+   * These simply don't merit individual tests.
+   *
+   * @covers ::setWebsite
+   * @covers ::getWebsite
+   * @covers ::setVersion
+   * @covers ::getVersion
+   * @covers ::setTitle
+   * @covers ::getTitle
+   */
+  public function testMetadataProps() {
+    $library = $this->getLibraryFixture();
+
+    $this->assertEquals('foo', $library->getTitle());
+    $this->assertEquals('1.2.3', $library->getVersion());
+    $this->assertEquals('http://foo.bar', $library->getWebsite());
+  }
+
+  /**
+   * @covers ::addDependency
+   */
   public function testAddDependency() {
     $library = $this->getLibraryFixture();
-    $library->addDependency('baz/bing');
-    $this->assertEquals($library->getDependencyInfo(), array('foo/bar', 'baz/bing'), 'Dependencies added to library successfully.');
+
+    $this->assertSame($library, $library->addDependency('foo/bar'));
+    $this->assertAttributeContains('foo/bar', 'dependencies', $library);
+
+    $invalid = array('foo', 'foo//bar', 0, 1.1, fopen(__FILE__, 'r'), TRUE, array(), new \stdClass);
+
+    try {
+      foreach ($invalid as $val) {
+        $library->addDependency($val, $val);
+        $this->fail('Was able to create an ordering relationship with an inappropriate value.');
+      }
+    } catch (\InvalidArgumentException $e) {}
+  }
+
+  /**
+   * @depends testAddDependency
+   * @covers ::hasDependencies
+   */
+  public function testHasDependencies() {
+    $library = $this->getLibraryFixture();
+    $this->assertFalse($library->hasDependencies());
+
+    $library->addDependency('foo/bar');
+    $this->assertTrue($library->hasDependencies());
+  }
+
+  /**
+   * @depends testAddDependency
+   * @covers ::getDependencyInfo
+   */
+  public function testGetDependencyInfo() {
+    $library = $this->getLibraryFixture();
+    $this->assertEmpty($library->getDependencyInfo());
+
+    $library->addDependency('foo/bar');
+    $this->assertEquals(array('foo/bar'), $library->getDependencyInfo());
   }
 
+  /**
+   * @depends testAddDependency
+   * @depends testHasDependencies
+   * @covers ::clearDependencies
+   */
   public function testClearDependencies() {
     $library = $this->getLibraryFixture();
-    $library->clearDependencies();
-    $this->assertEmpty($library->getDependencyInfo(), 'Dependencies recorded in the library were cleared correctly.');
+    $library->addDependency('foo/bar');
+
+    $this->assertSame($library, $library->clearDependencies());
+    $this->assertFalse($library->hasDependencies());
   }
 
-  public function testFrozenNonwriteability() {
+  /**
+   * @covers ::after
+   */
+  public function testAfter() {
     $library = $this->getLibraryFixture();
-    $library->freeze();
-    try {
-      $library->setTitle('bar');
-      $this->fail('No exception thrown when attempting to set a new title on a frozen library.');
-    }
-    catch (\LogicException $e) {}
+    $dep = $this->createStubFileAsset();
 
-    try {
-      $library->setVersion('2.3.4');
-      $this->fail('No exception thrown when attempting to set a new version on a frozen library.');
-    }
-    catch (\LogicException $e) {}
+    $this->assertSame($library, $library->after('foo'));
+    $this->assertSame($library, $library->after($dep));
 
-    try {
-      $library->setWebsite('http://bar.baz');
-      $this->fail('No exception thrown when attempting to set a new website on a frozen library.');
-    }
-    catch (\LogicException $e) {}
+    $this->assertAttributeContains($dep, 'predecessors', $library);
+
+    $invalid = array(0, 1.1, fopen(__FILE__, 'r'), TRUE, array(), new \stdClass);
 
     try {
-      $library->addDependency('bing', 'bang');
-      $this->fail('No exception thrown when attempting to add a new dependency on a frozen library.');
-    }
-    catch (\LogicException $e) {}
+      foreach ($invalid as $val) {
+        $library->after($val);
+        $this->fail('Was able to create an ordering relationship with an inappropriate value.');
+      }
+    } catch (\InvalidArgumentException $e) {}
+  }
+
+  /**
+   * @depends testAfter
+   * @covers ::hasPredecessors
+   */
+  public function testHasPredecessors() {
+    $library = $this->getLibraryFixture();
+    $this->assertFalse($library->hasPredecessors());
+
+    $library->after('foo');
+    $this->assertTrue($library->hasPredecessors());
+  }
+
+  /**
+   * @depends testAfter
+   * @covers ::getPredecessors
+   */
+  public function testGetPredecessors() {
+    $library = $this->getLibraryFixture();
+    $this->assertEmpty($library->getPredecessors());
+
+    $library->after('foo');
+    $this->assertEquals(array('foo'), $library->getPredecessors());
+  }
+
+  /**
+   * @depends testAfter
+   * @depends testHasPredecessors
+   * @covers ::clearPredecessors
+   */
+  public function testClearPredecessors() {
+    $library = $this->getLibraryFixture();
+    $library->after('foo');
+
+    $this->assertSame($library, $library->clearPredecessors());
+    $this->assertFalse($library->hasPredecessors());
+  }
+
+  /**
+   * @covers ::before
+   */
+  public function testBefore() {
+    $library = $this->getLibraryFixture();
+    $dep = $this->createStubFileAsset();
+
+    $this->assertSame($library, $library->before('foo'));
+    $this->assertSame($library, $library->before($dep));
+
+    $this->assertAttributeContains($dep, 'successors', $library);
+
+    $invalid = array(0, 1.1, fopen(__FILE__, 'r'), TRUE, array(), new \stdClass);
 
     try {
-      $library->clearDependencies();
-      $this->fail('No exception thrown when attempting to clear dependencies from a frozen library.');
+      foreach ($invalid as $val) {
+        $library->after($val);
+        $this->fail('Was able to create an ordering relationship with an inappropriate value.');
+      }
+    } catch (\InvalidArgumentException $e) {}
+  }
+
+  /**
+   * @depends testBefore
+   * @covers ::hasSuccessors
+   */
+  public function testHasSuccessors() {
+    $library = $this->getLibraryFixture();
+    $this->assertFalse($library->hasSuccessors());
+
+    $library->before('foo');
+    $this->assertTrue($library->hasSuccessors());
+  }
+
+  /**
+   * @depends testBefore
+   * @covers ::getSuccessors
+   */
+  public function testGetSuccessors() {
+    $library = $this->getLibraryFixture();
+    $this->assertEmpty($library->getSuccessors());
+
+    $library->before('foo');
+    $this->assertEquals(array('foo'), $library->getSuccessors());
+  }
+
+   /**
+   * @depends testBefore
+   * @covers ::clearSuccessors
+   */
+  public function testClearSuccessors() {
+    $library = $this->getLibraryFixture();
+    $library->before('foo');
+
+    $this->assertSame($library, $library->clearSuccessors());
+    $this->assertFalse($library->hasSuccessors());
+  }
+
+  /**
+   * Tests that all methods that should be disabled by freezing the collection
+   * correctly trigger an exception.
+   *
+   * @covers ::freeze
+   * @covers ::isFrozen
+   * @covers ::attemptWrite
+   */
+  public function testExceptionOnWriteWhenFrozen() {
+    $library = new AssetLibrary();
+    $write_protected = array(
+      'setTitle' => array('foo'),
+      'setVersion' => array('foo'),
+      'setWebsite' => array('foo'),
+      'addDependency' => array('foo/bar'),
+      'clearDependencies' => array(function() {}),
+      'after' => array('foo'),
+      'clearPredecessors' => array(),
+      'before' => array('foo'),
+      'clearSuccessors' => array(),
+    );
+
+    // No exception before freeze
+    list($method, $args) = each($write_protected);
+    call_user_func_array(array($library, $method), $args);
+
+    $library->freeze();
+    foreach ($write_protected as $method => $args) {
+      try {
+        call_user_func_array(array($library, $method), $args);
+        $this->fail(sprintf('Was able to run write method "%s" on frozen AssetLibrary', $method));
+      } catch (FrozenObjectException $e) {}
     }
-    catch (\LogicException $e) {}
   }
 }
diff --git a/core/tests/Drupal/Tests/Core/Asset/Collection/BasicAssetCollectionTest.php b/core/tests/Drupal/Tests/Core/Asset/Collection/BasicAssetCollectionTest.php
index fc89f8a..71345ba 100644
--- a/core/tests/Drupal/Tests/Core/Asset/Collection/BasicAssetCollectionTest.php
+++ b/core/tests/Drupal/Tests/Core/Asset/Collection/BasicAssetCollectionTest.php
@@ -38,6 +38,10 @@ public function getBasicCollection() {
   /**
    * Method to return the appropriate collection type for the current test.
    *
+   * If demonstrating adherence to Liskov is desired, this test class can be
+   * extended and this method swapped out to provide the correct
+   * AssetCollectionBasicInterface object for testing.
+   *
    * @return AssetCollectionBasicInterface
    */
   public function getCollection() {
@@ -73,7 +77,7 @@ public function getThreeLeafBasicCollection() {
   public function testAdd() {
     $collection = $this->getCollection();
     $asset = $this->createStubFileAsset();
-    $this->assertTrue($collection->add($asset));
+    $this->assertSame($collection, $collection->add($asset));
 
     $this->assertAttributeContains($asset, 'assetStorage', $collection);
     $this->assertAttributeContains($asset, 'assetIdMap', $collection);
@@ -88,20 +92,6 @@ public function testAdd() {
   }
 
   /**
-   * @depends testAdd
-   * @depends testEach
-   * @covers ::__construct
-   */
-  public function testCreateWithAssets() {
-    $asset1 = $this->createStubFileAsset();
-    $asset2 = $this->createStubFileAsset();
-    $collection = $this->getMockForAbstractClass('\\Drupal\\Core\\Asset\\Collection\\BasicAssetCollection', array(array($asset1, $asset2)));
-
-    $this->assertContains($asset1, $collection);
-    $this->assertContains($asset2, $collection);
-  }
-
-  /**
    * @expectedException \Drupal\Core\Asset\Exception\UnsupportedAsseticBehaviorException
    * @covers ::add
    */
@@ -128,6 +118,20 @@ public function testEach() {
 
   /**
    * @depends testAdd
+   * @depends testEach
+   * @covers ::__construct
+   */
+  public function testCreateWithAssets() {
+    $asset1 = $this->createStubFileAsset();
+    $asset2 = $this->createStubFileAsset();
+    $collection = $this->getMockForAbstractClass('\\Drupal\\Core\\Asset\\Collection\\BasicAssetCollection', array(array($asset1, $asset2)));
+
+    $this->assertContains($asset1, $collection);
+    $this->assertContains($asset2, $collection);
+  }
+
+  /**
+   * @depends testAdd
    * @covers ::eachLeaf
    * @covers \Drupal\Core\Asset\Collection\Iterator\RecursiveBasicCollectionIterator
    */
@@ -142,25 +146,6 @@ public function testEachLeaf() {
   }
 
   /**
-   * Tests that adding the same asset twice is disallowed.
-   *
-   * @depends testAdd
-   * @covers ::add
-   */
-  public function testDoubleAdd() {
-    $collection = $this->getCollection();
-    $asset = $this->createStubFileAsset();
-    $this->assertTrue($collection->add($asset));
-
-    // Test by object identity
-    $this->assertFalse($collection->add($asset));
-    // Test by id
-    $asset2 = $this->createStubFileAsset('css', $asset->id());
-
-    $this->assertFalse($collection->add($asset2));
-  }
-
-  /**
    * @depends testAdd
    * @covers ::contains
    */
@@ -185,7 +170,7 @@ public function testContains() {
    * @covers ::find
    * @expectedException \OutOfBoundsException
    */
-  public function testGetById() {
+  public function testFind() {
     $collection = $this->getCollection();
 
     $asset = $this->createStubFileAsset();
@@ -259,6 +244,58 @@ public function testRemove() {
   }
 
   /**
+   * @depends testAdd
+   * @depends testRemove
+   * @covers ::count
+   */
+  public function testCount() {
+    $collection = $this->getCollection();
+    $this->assertCount(0, $collection);
+
+    $collection->add($this->getAggregate());
+    $this->assertCount(0, $collection);
+
+    $aggregate = $this->getAggregate();
+    $asset = $this->createStubFileAsset();
+    $aggregate->add($asset);
+    $collection->add($aggregate);
+    $this->assertCount(1, $collection);
+
+    $collection->remove($aggregate);
+    $this->assertCount(0, $collection);
+
+    $collection->add($asset);
+    $this->assertCount(1, $collection);
+
+    $collection->remove($asset);
+    $this->assertCount(0, $collection);
+  }
+
+  /**
+   * Tests that adding the same asset twice results in just one asset.
+   *
+   * @depends testAdd
+   * @depends testCount
+   * @covers ::add
+   */
+  public function testDoubleAdd() {
+    $collection = $this->getCollection();
+    $asset = $this->createStubFileAsset();
+
+    $collection->add($asset);
+
+    // Test by object identity
+    $collection->add($asset);
+    $this->assertCount(1, $collection);
+
+    // Test by id
+    $asset2 = $this->createStubFileAsset('css', $asset->id());
+
+    $collection->add($asset2);
+    $this->assertCount(1, $collection);
+  }
+
+  /**
    * @depends testEach
    * @covers ::remove
    * @covers ::doRemove
@@ -396,34 +433,6 @@ public function testIsEmpty() {
   }
 
   /**
-   * @depends testAdd
-   * @depends testRemove
-   * @covers ::count
-   */
-  public function testCount() {
-    $collection = $this->getCollection();
-    $this->assertCount(0, $collection);
-
-    $collection->add($this->getAggregate());
-    $this->assertCount(0, $collection);
-
-    $aggregate = $this->getAggregate();
-    $asset = $this->createStubFileAsset();
-    $aggregate->add($asset);
-    $collection->add($aggregate);
-    $this->assertCount(1, $collection);
-
-    $collection->remove($aggregate);
-    $this->assertCount(0, $collection);
-
-    $collection->add($asset);
-    $this->assertCount(1, $collection);
-
-    $collection->remove($asset);
-    $this->assertCount(0, $collection);
-  }
-
-  /**
    * @covers ::remove
    */
   public function testRemoveInvalidNeedle() {