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.

Answer 1

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); // Use this if you are running PHP older than 8.1.0
  return $method;
}

public function testFoo() {
  $foo = self::getMethod('foo');
  $obj = new MyClass();
  $foo->invokeArgs($obj, array(...));
  ...
}

Answer 2

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)
             );

Answer 3

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.

Answer 4

I'd like to propose a slight variation to getMethod() defined in uckelman's answer.

This version changes getMethod() by removing hard-coded values and simplifying usage a little. I recommend adding it to your PHPUnitUtil class as in the example below or to your PHPUnit_Framework_TestCase-extending class (or, I suppose, globally to your PHPUnitUtil file).

Since MyClass is being instantiated anyways and ReflectionClass can take a string or an object...

class PHPUnitUtil {
    /**
     * Get a private or protected method for testing/documentation purposes.
     * How to use for MyClass->foo():
     *      $cls = new MyClass();
     *      $foo = PHPUnitUtil::getPrivateMethod($cls, 'foo');
     *      $foo->invoke($cls, $...);
     * @param object $obj The instantiated instance of your class
     * @param string $name The name of your private/protected method
     * @return ReflectionMethod The method you asked for
     */
    public static function getPrivateMethod($obj, $name) {
      $class = new ReflectionClass($obj);
      $method = $class->getMethod($name);
      // $method->setAccessible(true); // Use this if you are running PHP older than 8.1.0
      return $method;
    }
    // ... some other functions
}

I also created an alias function getProtectedMethod() to be explicit what is expected, but that one's up to you.

Answer 5

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).

Answer 6

You can indeed use __call() in a generic fashion to access protected methods. To be able to test this class

class Example {
    protected function getMessage() {
        return 'hello';
    }
}

you create a subclass in ExampleTest.php:

class ExampleExposed extends Example {
    public function __call($method, array $args = array()) {
        if (!method_exists($this, $method))
            throw new BadMethodCallException("method '$method' does not exist");
        return call_user_func_array(array($this, $method), $args);
    }
}

Note that the __call() method does not reference the class in any way so you can copy the above for each class with protected methods you want to test and just change the class declaration. You may be able to place this function in a common base class, but I haven't tried it.

Now the test case itself only differs in where you construct the object to be tested, swapping in ExampleExposed for Example.

class ExampleTest extends PHPUnit_Framework_TestCase {
    function testGetMessage() {
        $fixture = new ExampleExposed();
        self::assertEquals('hello', $fixture->getMessage());
    }
}

I believe PHP 5.3 allows you to use reflection to change the accessibility of methods directly, but I assume you'd have to do so for each method individually.

Answer 7

I'm going to throw my hat into the ring here:

I've used the __call hack with mixed degrees of success. The alternative I came up with was to use the Visitor pattern:

1: generate a stdClass or custom class (to enforce type)

2: prime that with the required method and arguments

3: ensure that your SUT has an acceptVisitor method which will execute the method with the arguments specified in the visiting class

4: inject it into the class you wish to test

5: SUT injects the result of operation into the visitor

6: apply your test conditions to the Visitor's result attribute

Answer 8

I suggest following workaround for "Henrik Paul"'s workaround/idea :)

You know names of private methods of your class. For example they are like _add(), _edit(), _delete() etc.

Hence when you want to test it from aspect of unit-testing, just call private methods by prefixing and/or suffixing some common word (for example _addPhpunit) so that when __call() method is called (since method _addPhpunit() doesn't exist) of owner class, you just put necessary code in __call() method to remove prefixed/suffixed word/s (Phpunit) and then to call that deduced private method from there. This is another good use of magic methods.

Try it out.

Answer 9

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

Answer 10

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!

Answer 11

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']);