public function testReturnsOutputShape()
 {
     $o = new Operation(['output' => ['shape' => 'os']], new ShapeMap(['os' => ['type' => 'structure']]));
     $os = $o->getOutput();
     $this->assertInstanceOf('Vws\\Api\\Shape', $os);
     $this->assertEquals('structure', $os->getType());
     $this->assertSame($os, $o->getOutput());
 }