Best practices to test protected methods with PHPUnit


Question

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.

1
268
5/23/2017 12:10:41 PM

Accepted Answer

If you're using PHP5 (>= 5.3.2) with PHPUnit, you can test your private and protected methods by using reflection to set them to be public prior to running your tests:

protected static function getMethod($name) {
  $class = new ReflectionClass('MyClass');
  $method = $class->getMethod($name);
  $method->setAccessible(true);
  return $method;
}

public function testFoo() {
  $foo = self::getMethod('foo');
  $obj = new MyClass();
  $foo->invokeArgs($obj, array(...));
  ...
}
394
10/24/2010 10:49:41 AM

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.


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