An article with some actual code in it! That'd become a rarity. This is actuallya real-world challenge I'm faced with in backfilling some unit tests. Yeah, I know I'm an advocate of TDD so that should mean there's no "backfilling" of tests: they all get done up front. But for reasons I won't go into... I'm backfilling testing for this function.
Here's the function:
public static function loadValidatorMetadata(ClassMetadata $metadata)
{
$metadata->addPropertyConstraint('languageId', new Assert\Range(
['min' => 1, 'max' => self::$maxLegacyLanguageId]
));
$metadata->addPropertyConstraint('destinationId', new Assert\Range(['min' => 1]));
$metadata->addConstraint(new Assert\Callback('validateArrivalDate'));
$metadata->addConstraint(new Assert\Callback('validateNights'));
$metadata->addPropertyConstraint('firstName', new Assert\NotBlank());
$metadata->addPropertyConstraint('firstName', new Assert\Length(
['min' => 1, 'max' => GroupEnquiryRepository::SHORT_STRING_MAX_LENGTH]
));
$metadata->addPropertyConstraint('surName', new Assert\NotBlank());
$metadata->addPropertyConstraint('surName', new Assert\Length(
['min' => 1, 'max' => GroupEnquiryRepository::SHORT_STRING_MAX_LENGTH]
));
$metadata->addPropertyConstraint('email', new Assert\NotBlank());
$metadata->addPropertyConstraint('email', new Assert\Email());
$metadata->addPropertyConstraint('groupTypeId', new Assert\Range(['min' => 1]));
$metadata->addPropertyConstraint('groupSize', new Assert\NotNull());
$metadata->addPropertyConstraint('groupSize', new Assert\Range(
['min' => GroupEnquiryService::MIN_GROUPS_THRESHOLD, 'max' => BookingService::MAXIMUM_PEOPLE]
));
$metadata->addPropertyConstraint('youngestAge', new Assert\Range(
['min' => 1, 'max' => GroupEnquiryService::MAX_AGE]
));
$metadata->addPropertyConstraint('telephoneCountryCode', new Assert\NotBlank());
$metadata->addPropertyConstraint('telephoneCountryCode', new Assert\Length(
['min' => 1, 'max' => GroupEnquiryRepository::SHORT_STRING_MAX_LENGTH]
));
$metadata->addPropertyConstraint('phone', new Assert\NotBlank());
$metadata->addPropertyConstraint('phone', new Assert\Length(
['min' => GroupEnquiryService::MIN_TELEPHONE_NUMBER_LENGTH]
));
$metadata->addConstraint(new Assert\Callback('validateMobileCountryCode'));
$metadata->addConstraint(new Assert\Callback('validateMobile'));
$metadata->addConstraint(new Assert\Callback('validateAdditionalInfo'));
}
First things first: yeah, normally I'd not write a function that's 40-odd lines long, but in this case there's very little actual logic, plus it's only setting some validation config. BTW this is using the Symfony 2 validation framework (Symfony: validation), as implemented by the Silex microframework (ValidatorServiceProvider: validating objects).
To provide context, we have a class - basically a validation bean - thus:
class GroupEnquiry
{
public $languageId;
public $destinationId;
public $arrivalDate;
public $nights;
public $firstName;
public $surName;
public $email;
public $telephoneCountryCode;
public $phone;
public $mobileCountryCode;
public $mobile;
public $groupTypeId;
public $groupSize;
public $youngestAge;
public $additionalInfo;
}
And that
loadValidatorMetadata() function provides the constraints for Symfony to enforce. As you can see: there's range validation, existence validation, length validation, date validation, and a coupla compound constraints implemented via callbacks.So, anyway, I need to write the testing for
loadValidatorMetadata(). Initially I was staring at the code going and going "how the hell?".Then I thought: I'll assert the
addConstraint() and addPropertyConstraint() methods are called for the correct properties, and the correct number of times. But that seemed unhelpful. What's the point of checking that some constraint is applied to a property, but not checking what sort of constraint. IT all seemed too contrived.Then I thought that the constraints themselves don't need testing here because I'm either testing our callbacks elsewhere, or Symfony have done their own testing. In theory this is a fine notion, but in reality it does not actually help me test our validation code works.
I was stumped as to how to test this stuff, without basically replicating the function in parallel for test. And that clearly sucks as far as effort and common sense goes. It was the wrong approach.