Scientist\Experiment::control PHP Method

    public function control(callable $callback)
    {
        $this->control = $callback;
        return $this;
    }

 public function test_that_running_experiment_with_no_laboratory_executes_control()
 {
     $e = new Experiment('test experiment');
     $e->control(function () {
         return 'foo';
     });
     $v = $e->run();
     $this->assertEquals('foo', $v);
 }