minor #39775 [WIP] Use ::class keyword when possible (fabpot)

This PR was merged into the 4.4 branch.

Discussion
----------

[WIP] Use ::class keyword when possible

| Q             | A
| ------------- | ---
| Branch?       | 4.4 <!-- see below -->
| Bug fix?      | no
| New feature?  | no <!-- please update src/**/CHANGELOG.md files -->
| Deprecations? | no <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tickets       | n/a  <!-- prefix each issue number with "Fix #", no need to create an issue if none exist, explain below instead -->
| License       | MIT
| Doc PR        | n/a

Commits
-------

036a36cb14 Use ::class keyword when possible

Author: fabpot

Tests/GenericEventTest.php

@@ -80,7 +80,7 @@ public function testGetArgument()
 
     public function testGetArgException()
     {
-        $this->expectException('\InvalidArgumentException');
+        $this->expectException(\InvalidArgumentException::class);
         $this->event->getArgument('nameNotExist');
     }
 
@@ -90,7 +90,7 @@ public function testOffsetGet()
         $this->assertEquals('Event', $this->event['name']);
 
         // test getting invalid arg
-        $this->expectException('InvalidArgumentException');
+        $this->expectException(\InvalidArgumentException::class);
         $this->assertFalse($this->event['nameNotExist']);
     }
 

Tests/ImmutableEventDispatcherTest.php

@@ -72,27 +72,27 @@ public function testHasListenersDelegates()
 
     public function testAddListenerDisallowed()
     {
-        $this->expectException('\BadMethodCallException');
+        $this->expectException(\BadMethodCallException::class);
         $this->dispatcher->addListener('event', function () { return 'foo'; });
     }
 
     public function testAddSubscriberDisallowed()
     {
-        $this->expectException('\BadMethodCallException');
+        $this->expectException(\BadMethodCallException::class);
         $subscriber = $this->getMockBuilder('Symfony\Component\EventDispatcher\EventSubscriberInterface')->getMock();
 
         $this->dispatcher->addSubscriber($subscriber);
     }
 
     public function testRemoveListenerDisallowed()
     {
-        $this->expectException('\BadMethodCallException');
+        $this->expectException(\BadMethodCallException::class);
         $this->dispatcher->removeListener('event', function () { return 'foo'; });
     }
 
     public function testRemoveSubscriberDisallowed()
     {
-        $this->expectException('\BadMethodCallException');
+        $this->expectException(\BadMethodCallException::class);
         $subscriber = $this->getMockBuilder('Symfony\Component\EventDispatcher\EventSubscriberInterface')->getMock();
 
         $this->dispatcher->removeSubscriber($subscriber);