public function testTags()
 {
     $this->assertEmpty($this->_sut->findTags());
     $this->assertEmpty($this->_sut->findTaggedServiceIds('bar'));
     $this->_sut->register('x', 'foo')->addTag('bar', array('some', 'attributes'));
     $this->assertEquals(array('bar'), $this->_sut->findTags());
     $this->assertEquals(array('x' => array(array('some', 'attributes'))), $this->_sut->findTaggedServiceIds('bar'));
 }