Neos\Flow\Mvc\Controller\Argument::setValidator PHP Method

    public function setValidator(ValidatorInterface $validator)
    {
        $this->validator = $validator;
        return $this;
    }

 /**
  * @test
  */
 public function setValueShouldSetValidationErrorsIfValidatorIsSetAndValidationFailed()
 {
     $error = new FLowError\Error('Some Error', 1234);
     $mockValidator = $this->createMock(ValidatorInterface::class);
     $validationMessages = new FLowError\Result();
     $validationMessages->addError($error);
     $mockValidator->expects($this->once())->method('validate')->with('convertedValue')->will($this->returnValue($validationMessages));
     $this->simpleValueArgument->setValidator($mockValidator);
     $this->setupPropertyMapperAndSetValue();
     $this->assertEquals([$error], $this->simpleValueArgument->getValidationResults()->getErrors());
 }