diff --git a/src/Core/PluginInterface.php b/src/Core/PluginInterface.php
index 9f940ab2465..8ca539bc682 100644
--- a/src/Core/PluginInterface.php
+++ b/src/Core/PluginInterface.php
@@ -18,6 +18,14 @@
  */
 interface PluginInterface
 {
+    /**
+     * Load all the application configuration and bootstrap logic.
+     *
+     * Override this method to add additional bootstrap logic for your application.
+     *
+     * @return void
+     */
+    public function bootstrap();
 
     /**
      * Disables route loading for the plugin
diff --git a/src/Core/PluginRegistry.php b/src/Core/PluginRegistry.php
index 500cf3c7d9e..52082470456 100644
--- a/src/Core/PluginRegistry.php
+++ b/src/Core/PluginRegistry.php
@@ -20,7 +20,7 @@
 /**
  * Plugin Registry
  */
-class PluginRegistry extends ObjectRegistry implements ConsoleApplicationInterface, HttpApplicationInterface
+class PluginRegistry extends ObjectRegistry implements PluginRegistryInterface
 {
 
     /**
@@ -79,7 +79,7 @@ protected function _create($class, $alias, $config)
         if ((!$instance instanceof HttpApplicationInterface
             && !$instance instanceof ConsoleApplicationInterface)
             || !$instance instanceof PluginInterface) {
-            throw new \RuntimeException(sprintf(
+            throw new RuntimeException(sprintf(
                 '`%s` is not a valid plugin object. It\'s not implementing `%s` or `%s`',
                 get_class($instance)),
                 HttpApplicationInterface::class,
diff --git a/src/Core/PluginRegistryInterface.php b/src/Core/PluginRegistryInterface.php
new file mode 100644
index 00000000000..81142a3b268
--- /dev/null
+++ b/src/Core/PluginRegistryInterface.php
@@ -0,0 +1,29 @@
+<?php
+/**
+ * CakePHP(tm) : Rapid Development Framework (https://cakephp.org)
+ * Copyright 2005-2011, Cake Software Foundation, Inc. (https://cakefoundation.org)
+ * Licensed under The MIT License
+ * Redistributions of files must retain the above copyright notice.
+ *
+ * @copyright     Copyright (c) Cake Software Foundation, Inc. (https://cakefoundation.org)
+ * @link          https://cakephp.org CakePHP(tm) Project
+ * @since         3.6.0
+ * @license       https://opensource.org/licenses/mit-license.php MIT License
+ */
+
+namespace Cake\Core;
+
+use Countable;
+use IteratorAggregate;
+
+/**
+ * Plugin Registry Interface
+ */
+interface PluginRegistryInterface extends
+    Countable,
+    IteratorAggregate,
+    ConsoleApplicationInterface,
+    HttpApplicationInterface
+{
+
+}
diff --git a/src/Http/BaseApplication.php b/src/Http/BaseApplication.php
index c630843688d..4ee43366718 100644
--- a/src/Http/BaseApplication.php
+++ b/src/Http/BaseApplication.php
@@ -17,8 +17,10 @@
 use Cake\Core\ConsoleApplicationInterface;
 use Cake\Core\HttpApplicationInterface;
 use Cake\Core\PluginRegistry;
+use Cake\Core\PluginRegistryInterface;
 use Cake\Routing\DispatcherFactory;
 use Cake\Routing\Router;
+use InvalidArgumentException;
 use Psr\Http\Message\ResponseInterface;
 use Psr\Http\Message\ServerRequestInterface;
 
@@ -42,17 +44,51 @@ abstract class BaseApplication implements ConsoleApplicationInterface, HttpAppli
      *
      * @param \Cake\Core\PluginRegistry
      */
-    protected $plugins;
+    protected $pluginRegistry;
+
+    /**
+     * Default Plugin Registry Class
+     *
+     * @var string
+     */
+    protected $defaultPluginRegistry = PluginRegistry::class;
 
     /**
      * Constructor
      *
      * @param string $configDir The directory the bootstrap configuration is held in.
+     * @param string|null $pluginRegistry Plugin Registry Object
      */
-    public function __construct($configDir)
+    public function __construct($configDir, $pluginRegistry = null)
     {
         $this->configDir = $configDir;
-        $this->plugins = new PluginRegistry();
+
+        $this->setPluginRegistry($pluginRegistry);
+    }
+
+    /**
+     * Sets the plugin registry
+     *
+     * @param string|null $pluginRegistry Plugin Registry Object
+     * @return void
+     */
+    public function setPluginRegistry($pluginRegistry = null)
+    {
+        if (empty($pluginRegistry)) {
+            $this->pluginRegistry = new $this->defaultPluginRegistry();
+
+            return;
+        }
+
+        if (!$pluginRegistry instanceof PluginRegistryInterface) {
+            throw new InvalidArgumentException(sprintf(
+                '`%s` is not an instance of `%s`',
+                get_class($pluginRegistry),
+                PluginRegistryInterface::class
+            ));
+        }
+
+        $this->pluginRegistry = $pluginRegistry;
     }
 
     /**
@@ -134,6 +170,6 @@ protected function getDispatcher()
      */
     public function plugins()
     {
-        return $this->plugins;
+        return $this->pluginRegistry;
     }
 }