Avoid PHPUnit warnings by using dummy assertions

Author: clue

tests/AbstractLoopTest.php

@@ -262,6 +262,8 @@ public function testRemoveInvalid()
         // remove a valid stream from the event loop that was never added in the first place
         $this->loop->removeReadStream($stream);
         $this->loop->removeWriteStream($stream);
+
+        $this->assertTrue(true);
     }
 
     /** @test */

tests/Timer/TimersTest.php

@@ -25,5 +25,7 @@ public function testBlockedTimer()
         }));
 
         $timers->tick();
+
+        $this->assertTrue(true);
     }
 }