Update MissingAction test to inflect class name.

src/Template/Error/missing_action.ctp

@@ -32,13 +32,13 @@ if (isset($controller)) {
     $baseClass = $namespace . '\Controller\AppController';
     $extends = 'AppController';
     $type = 'Controller';
-    $class = $controller;
+    $class = Inflector::camelize($controller);
 }
 // Mailer MissingActionException support
 if (isset($mailer)) {
     $baseClass = 'Cake\Mailer\Mailer';
     $type = $extends = 'Mailer';
-    $class = $mailer;
+    $class = Inflector::camelize($mailer);
 }
 
 if (empty($plugin)) {

tests/TestCase/Error/ExceptionRendererTest.php

@@ -580,6 +580,19 @@ class ExceptionRendererTest extends TestCase
         return [
             [
                 new MissingActionException([
+                    'controller' => 'postsController',
+                    'action' => 'index',
+                    'prefix' => '',
+                    'plugin' => '',
+                ]),
+                [
+                    '/Missing Method in PostsController/',
+                    '/<em>PostsController::index\(\)<\/em>/'
+                ],
+                404
+            ],
+            [
+                new MissingActionException([
                     'controller' => 'PostsController',
                     'action' => 'index',
                     'prefix' => '',