diff --git a/src/Entity/FeaturesBundle.php b/src/Entity/FeaturesBundle.php
index c06d31f..f134e50 100644
--- a/src/Entity/FeaturesBundle.php
+++ b/src/Entity/FeaturesBundle.php
@@ -208,6 +208,9 @@ class FeaturesBundle extends ConfigEntityBase implements FeaturesBundleInterface
     foreach ($this->assignments as $method_id => &$method) {
       $method['enabled'] = in_array($method_id, $assignments);
     }
+    foreach (array_diff($assignments, array_keys($this->assignments)) as $method_id) {
+      $this->assignments[$method_id] = ['enabled' => TRUE];
+    }
   }
 
   /**
diff --git a/tests/src/Unit/FeaturesBundleTest.php b/tests/src/Unit/FeaturesBundleTest.php
new file mode 100644
index 0000000..a1d8930
--- /dev/null
+++ b/tests/src/Unit/FeaturesBundleTest.php
@@ -0,0 +1,131 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Tests\features\Unit\FeaturesBundleTest.
+ */
+
+namespace Drupal\Tests\features\Unit;
+
+use Drupal\features\Entity\FeaturesBundle;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * @coversDefaultClass Drupal\features\Entity\FeaturesBundle
+ * @group features
+ */
+class FeaturesBundleTest extends UnitTestCase {
+  /**
+   * Test that assignments can be set and get.
+   */
+  function testAssignmentSetting() {
+    // Create an entity.
+    $settings = [
+      'foo' => [
+        'enabled' => TRUE,
+        'weight' => 0,
+        'my_setting' => 42,
+      ],
+      'bar' => [
+        'enabled' => FALSE,
+        'weight' => 1,
+        'another_setting' => 'value',
+      ],
+    ];
+    $bundle = new FeaturesBundle([
+      'assignments' => $settings,
+    ], 'features_bundle');
+
+    // Get assignments and attributes.
+    $this->assertArrayEquals(
+      $bundle->getEnabledAssignments(),
+      ['foo' => 'foo'],
+      'Can get enabled assignments'
+    );
+    $this->assertArrayEquals(
+      $bundle->getAssignmentWeights(),
+      ['foo' => 0, 'bar' => 1],
+      'Can get assignment weights'
+    );
+    $this->assertArrayEquals(
+      $bundle->getAssignmentSettings('foo'),
+      $settings['foo'],
+      'Can get assignment settings'
+    );
+    $this->assertArrayEquals(
+      $bundle->getAssignmentSettings(),
+      $settings,
+      'Can get all assignment settings'
+    );
+
+    // Change settings.
+    $settings['foo']['my_setting'] = 97;
+    $bundle->setAssignmentSettings('foo', $settings['foo']);
+    $this->assertArrayEquals(
+      $bundle->getAssignmentSettings('foo'),
+      $settings['foo'],
+      'Can change assignment settings'
+    );
+
+    // Change weights.
+    $settings['foo']['weight'] = 1;
+    $settings['bar']['weight'] = 0;
+    $bundle->setAssignmentWeights(['foo' => 1, 'bar' => 0]);
+    $this->assertArrayEquals(
+      $bundle->getAssignmentWeights(),
+      ['foo' => 1, 'bar' => 0],
+      'Can change assignment weights'
+    );
+    $this->assertArrayEquals(
+      $bundle->getAssignmentSettings(),
+      $settings,
+      'Weight changes are reflected in settings'
+    );
+
+    // Enable existing assignment.
+    $settings['bar']['enabled'] = TRUE;
+    $bundle->setEnabledAssignments(['foo', 'bar']);
+    $this->assertArrayEquals(
+      $bundle->getEnabledAssignments(),
+      ['foo' => 'foo', 'bar' => 'bar'],
+      'Can enable assignment'
+    );
+    $this->assertArrayEquals(
+      $bundle->getAssignmentSettings(),
+      $settings,
+      'Enabled assignment status is reflected in settings'
+    );
+
+    // Disable existing assignments.
+    $settings['foo']['enabled'] = FALSE;
+    $settings['bar']['enabled'] = FALSE;
+    $bundle->setEnabledAssignments([]);
+    $this->assertArrayEquals(
+      $bundle->getEnabledAssignments(),
+      [],
+      'Can disable assignments'
+    );
+    $this->assertArrayEquals(
+      $bundle->getAssignmentSettings(),
+      $settings,
+      'Disabled assignment status is reflected in settings'
+    );
+
+    // Enable a new assignment.
+    $settings['foo']['enabled'] = TRUE;
+    $settings['iggy']['enabled'] = TRUE;
+    $bundle->setEnabledAssignments(['foo', 'iggy']);
+    $this->assertArrayEquals(
+      $bundle->getEnabledAssignments(),
+      ['foo' => 'foo', 'iggy' => 'iggy'],
+      'Can enable new assignment'
+    );
+    $this->assertArrayEquals(
+      $bundle->getAssignmentSettings(),
+      $settings,
+      'New enabled assignment status is reflected in settings'
+    );
+
+  }
+
+}