public function testGettingToken()
 {
     $t1 = new WordToken('a');
     $t2 = new WordToken('b');
     $r = new TokenRegistry();
     $r->add($t1);
     $r->add($t2);
     $this->assertSame($t2, $r->getTokenWithKey(1));
     $this->assertNull($r->getTokenWithKey(2));
 }