public function testIsNaryConsumer()
 {
     $consumer = Callables::newConsumer(function ($a, $b, $c) {
         return false;
     });
     $this->assertFalse(Callables::isUnaryConsumer($consumer));
     $this->assertFalse(Callables::isBinaryConsumer($consumer));
     $this->assertTrue(Callables::isNaryConsumer($consumer));
 }