Best practices to test protected methods with PHPUnit

GrGr_32679 0
Viewed 159058

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.

phpunit unit-testing php
11 Answers

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.

user_181800

I think troelskn is close. I would do this instead:

class ClassToTest
{
   protected function testThisMethod()
   {
     // Implement stuff here
   }
}

Then, implement something like this:

class TestClassToTest extends ClassToTest
{
  public function testThisMethod()
  {
    return parent::testThisMethod();
  }
}

You then run your tests against TestClassToTest.

It should be possible to automatically generate such extension classes by parsing the code. I wouldn't be surprised if PHPUnit already offers such a mechanism (though I haven't checked).

Michael_Johnson_176880

Alternative.The code below is provided as an example. Its implementation can be much broader. Its implementation that will help you test private methods and replacing a private property .

    <?php
    class Helper{
        public static function sandbox(\Closure $call,$target,?string $slaveClass=null,...$args)
        {
            $slaveClass=!empty($slaveClass)?$slaveClass:(is_string($target)?$target:get_class($target));
            $target=!is_string($target)?$target:null;
            $call=$call->bindTo($target,$slaveClass);
            return $call(...$args);
        }
    }
    class A{
        private $prop='bay';
        public function get()
        {
            return $this->prop;    
        }
        
    }
    class B extends A{}
    $b=new B;
    $priv_prop=Helper::sandbox(function(...$args){
        return $this->prop;
    },$b,A::class);
    
    var_dump($priv_prop);// bay
    
    Helper::sandbox(function(...$args){
        $this->prop=$args[0];
    },$b,A::class,'hello');
    var_dump($b->get());// hello
user_119035190

You can use Closure as in the code below

<?php

class A
{
    private string $value = 'Kolobol';
    private string $otherPrivateValue = 'I\'m very private, like a some kind of password!';

    public function setValue(string $value): void
    {
        $this->value = $value;
    }

    private function getValue(): string
    {
        return $this->value . ': ' . $this->getVeryPrivate();
    }

    private function getVeryPrivate()
    {
        return $this->otherPrivateValue;
    }
}

$getPrivateProperty = function &(string $propName) {
    return $this->$propName;
};

$getPrivateMethod = function (string $methodName) {
    return Closure::fromCallable([$this, $methodName]);
};

$objA = new A;
$getPrivateProperty = Closure::bind($getPrivateProperty, $objA, $objA);
$getPrivateMethod = Closure::bind($getPrivateMethod, $objA, $objA);
$privateByLink = &$getPrivateProperty('value');
$privateMethod = $getPrivateMethod('getValue');

echo $privateByLink, PHP_EOL; // Kolobok

$objA->setValue('Zmey-Gorynich');
echo $privateByLink, PHP_EOL; // Zmey-Gorynich

$privateByLink = 'Alyonushka';
echo $privateMethod(); // Alyonushka: I'm very private, like a some kind of password!
user_133633160

I made a class for invoking easily private methods (static and non-static) for unit-testing purposes:

class MethodInvoker
{
    public function invoke($object, string $methodName, array $args=[]) {
        $privateMethod = $this->getMethod(get_class($object), $methodName);

        return $privateMethod->invokeArgs($object, $args);
    }

    private function getMethod(string $className, string $methodName) {
        $class = new \ReflectionClass($className);
        
        $method = $class->getMethod($methodName);
        $method->setAccessible(true);
    
        return $method;
    }
}

Example of usage:

class TestClass {
    private function privateMethod(string $txt) {
        print_r('invoked privateMethod: ' . $txt);
    }
}

(new MethodInvoker)->invoke(new TestClass, 'privateMethod', ['argument_1']);
user_63944040
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