diff --git a/core/tests/Drupal/Tests/Component/Plugin/Factory/ReflectionFactoryTest.php b/core/tests/Drupal/Tests/Component/Plugin/Factory/ReflectionFactoryTest.php
new file mode 100644
index 0000000..d6cc8c6
--- /dev/null
+++ b/core/tests/Drupal/Tests/Component/Plugin/Factory/ReflectionFactoryTest.php
@@ -0,0 +1,215 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Tests\Component\Plugin\Factory\ReflectionFactoryTest.
+ *
+ * Also contains Argument* classes used as data for testing.
+ */
+
+namespace Drupal\Tests\Component\Plugin\Factory;
+
+use Drupal\Component\Plugin\Factory\ReflectionFactory;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * @group Plugin
+ * @coversDefaultClass Drupal\Component\Plugin\Factory\ReflectionFactory
+ */
+class ReflectionFactoryTest extends UnitTestCase {
+
+  /**
+   * Data provider for testGetInstanceArguments.
+   *
+   * The classes used here are defined at the bottom of this file.
+   *
+   * @return array
+   *   - Expected output.
+   *   - Class to reflect for input to getInstanceArguments().
+   *   - $plugin_id parameter to getInstanceArguments().
+   *   - $plugin_definition parameter to getInstanceArguments().
+   *   - $configuration parameter to getInstanceArguments().
+   */
+  public function providerGetInstanceArguments() {
+    return [
+      [
+        ['arguments_plugin_id'],
+        'Drupal\Tests\Component\Plugin\Factory\ArgumentsPluginId',
+        'arguments_plugin_id',
+        ['arguments_plugin_id' => ['class' => 'Drupal\Tests\Component\Plugin\Factory\ArgumentsPluginId']],
+        [],
+      ],
+      [
+        [[], ['arguments_many' => ['class' => 'Drupal\Tests\Component\Plugin\Factory\ArgumentsMany']], 'arguments_many', 'default_value', 'what_default'],
+        'Drupal\Tests\Component\Plugin\Factory\ArgumentsMany',
+        'arguments_many',
+        ['arguments_many' => ['class' => 'Drupal\Tests\Component\Plugin\Factory\ArgumentsMany']],
+        [],
+      ],
+      [
+        // Config array key exists and is set.
+        ['thing'],
+        'Drupal\Tests\Component\Plugin\Factory\ArgumentsConfigArrayKey',
+        'arguments_config_array_key',
+        ['arguments_config_array_key' => ['class' => 'Drupal\Tests\Component\Plugin\Factory\ArgumentsConfigArrayKey']],
+        ['config_name' => 'thing'],
+      ],
+      [
+        // Config array key exists and is not set.
+        [NULL],
+        'Drupal\Tests\Component\Plugin\Factory\ArgumentsConfigArrayKey',
+        'arguments_config_array_key',
+        ['arguments_config_array_key' => ['class' => 'Drupal\Tests\Component\Plugin\Factory\ArgumentsConfigArrayKey']],
+        ['config_name' => NULL],
+      ],
+      [
+        // Touch the else clause at the end of the method.
+        [NULL, NULL, NULL, NULL],
+        'Drupal\Tests\Component\Plugin\Factory\ArgumentsAllNull',
+        'arguments_all_null',
+        ['arguments_all_null' => ['class' => 'Drupal\Tests\Component\Plugin\Factory\ArgumentsAllNull']],
+        [],
+      ],
+      [
+        // A plugin with no constructor.
+        [NULL, NULL, NULL, NULL],
+        'Drupal\Tests\Component\Plugin\Factory\ArgumentsNoConstructor',
+        'arguments_no_constructor',
+        ['arguments_no_constructor' => ['class' => 'Drupal\Tests\Component\Plugin\Factory\ArgumentsNoConstructor']],
+        [],
+      ],
+    ];
+  }
+
+  /**
+   * @covers ::createInstance
+   * @dataProvider providerGetInstanceArguments
+   */
+  public function testCreateInstance($expected, $reflector_name, $plugin_id, $plugin_definition, $configuration) {
+    // Create a mock DiscoveryInterface which can return our plugin definition.
+    $mock_discovery = $this->getMockBuilder('Drupal\Component\Plugin\Discovery\DiscoveryInterface')
+      ->setMethods(array('getDefinition', 'getDefinitions', 'hasDefinition'))
+      ->getMock();
+    $mock_discovery->expects($this->never())->method('getDefinitions');
+    $mock_discovery->expects($this->never())->method('hasDefinition');
+    $mock_discovery->expects($this->once())
+      ->method('getDefinition')
+      ->willReturn($plugin_definition);
+
+    // Create a stub ReflectionFactory object. We use StubReflectionFactory
+    // because createInstance() has a dependency on a static method.
+    // StubReflectionFactory overrides this static method.
+    $reflection_factory = new StubReflectionFactory($mock_discovery);
+
+    // Finally test that createInstance() returns an object of the class we
+    // want.
+    $this->assertInstanceOf($reflector_name, $reflection_factory->createInstance($plugin_id));
+  }
+
+  /**
+   * @covers ::getInstanceArguments
+   * @dataProvider providerGetInstanceArguments
+   */
+  public function testGetInstanceArguments($expected, $reflector_name, $plugin_id, $plugin_definition, $configuration) {
+    $reflection_factory = $this->getMockBuilder('Drupal\Component\Plugin\Factory\ReflectionFactory')
+      ->disableOriginalConstructor()
+      ->getMock();
+    $get_instance_arguments_ref = new \ReflectionMethod($reflection_factory, 'getInstanceArguments');
+    $get_instance_arguments_ref->setAccessible(TRUE);
+
+    // Special case for plugin class without a constructor.
+    // getInstanceArguments() throws an exception if there's no constructor.
+    // This is not a documented behavior of getInstanceArguments(), but allows
+    // us to use one data set for this test method as well as
+    // testCreateInstance().
+    if ($plugin_id == 'arguments_no_constructor') {
+      $this->setExpectedException('\ReflectionException');
+    }
+
+    // Finally invoke getInstanceArguments() on our mocked factory.
+    $ref = new \ReflectionClass($reflector_name);
+    $result = $get_instance_arguments_ref->invoke(
+      $reflection_factory, $ref, $plugin_id, $plugin_definition, $configuration);
+    $this->assertEquals($expected, $result);
+  }
+
+}
+
+/**
+ * Override ReflectionFactory because ::createInstance() calls a static method.
+ *
+ * We have to override getPluginClass so that we can stub out its return value.
+ */
+class StubReflectionFactory extends ReflectionFactory {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getPluginClass($plugin_id, $plugin_definition = NULL, $required_interface = NULL) {
+    // Return the class name from the plugin definition.
+    return $plugin_definition[$plugin_id]['class'];
+  }
+}
+
+/**
+ * A stub class used by testGetInstanceArguments().
+ *
+ * @see providerGetInstanceArguments()
+ */
+class ArgumentsPluginId {
+
+  public function __construct($plugin_id) {
+    // No-op.
+  }
+
+}
+
+/**
+ * A stub class used by testGetInstanceArguments().
+ *
+ * @see providerGetInstanceArguments()
+ */
+class ArgumentsMany {
+
+  public function __construct(
+  $configuration, $plugin_definition, $plugin_id, $foo = 'default_value', $what_am_i_doing_here = 'what_default'
+  ) {
+    // No-op.
+  }
+
+}
+
+/**
+ * A stub class used by testGetInstanceArguments().
+ *
+ * @see providerGetInstanceArguments()
+ */
+class ArgumentsConfigArrayKey {
+
+  public function __construct($config_name) {
+    // No-op.
+  }
+
+}
+
+/**
+ * A stub class used by testGetInstanceArguments().
+ *
+ * @see providerGetInstanceArguments()
+ */
+class ArgumentsAllNull {
+
+  public function __construct($charismatic, $demure, $delightful, $electrostatic) {
+    // No-op.
+  }
+
+}
+
+/**
+ * A stub class used by testGetInstanceArguments().
+ *
+ * @see providerGetInstanceArguments()
+ */
+class ArgumentsNoConstructor {
+
+}