Best practices to test protected methods with PHPUnit

Asked 2008-10-30T09:32:41.713

361

I found the discussion on Do you test private method informative.

I have decided, that in some classes, I want to have protected methods, but test them. Some of these methods are static and short. Because most of the public methods make use of them, I will probably be able to safely remove the tests later. But for starting with a TDD approach and avoid debugging, I really want to test them.

I thought of the following:

Method Object as adviced in an answer seems to be overkill for this.
Start with public methods and when code coverage is given by higher level tests, turn them protected and remove the tests.
Inherit a class with a testable interface making protected methods public

Which is best practice? Is there anything else?

It seems, that JUnit automatically changes protected methods to be public, but I did not have a deeper look at it. PHP does not allow this via reflection.

php unit-testing phpunit

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2 Answers

teastburn has the right approach. Even simpler is to call the method directly and return the answer:

class PHPUnitUtil
{
  public static function callMethod($obj, $name, array $args) {
        $class = new \ReflectionClass($obj);
        $method = $class->getMethod($name);
        // $method->setAccessible(true); // Use this if you are running PHP older than 8.1.0
        return $method->invokeArgs($obj, $args);
    }
}

You can call this simply in your tests by:

$returnVal = PHPUnitUtil::callMethod(
                $this->object,
                '_nameOfProtectedMethod', 
                array($arg1, $arg2)
             );

answered 2012-01-02T15:06:37.563

You seem to be aware already, but I'll just restate it anyway; It's a bad sign, if you need to test protected methods. The aim of a unit test, is to test the interface of a class, and protected methods are implementation details. That said, there are cases where it makes sense. If you use inheritance, you can see a superclass as providing an interface for the subclass. So here, you would have to test the protected method (But never a private one). The solution to this, is to create a subclass for testing purpose, and use this to expose the methods. Eg.:

class Foo {
  protected function stuff() {
    // secret stuff, you want to test
  }
}

class SubFoo extends Foo {
  public function exposedStuff() {
    return $this->stuff();
  }
}

Note that you can always replace inheritance with composition. When testing code, it's usually a lot easier to deal with code that uses this pattern, so you may want to consider that option.

answered 2008-10-30T10:46:19.207

Best practices to test protected methods with PHPUnit

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