README

FuncMocker – Mocking PHP functions like a... punk rocker?

Allows you to overwrite (i.e., mock) global functions used within a given namespace for the purposes of testing.

There are two main use cases I developed this for:

1. When you are testing objects that call non-deterministic functions like time() and rand(), and you need these functions to return deterministic values for the sake of the test.
2. When you are working with code where you have objects that must make calls to functions. This is pretty common in legacy codebases that were not previously object-oriented in nature. For example, if you're project has a function called db_add() that you end up using in an object in your model layer, you might want to "mock" that function when you are testing so you don't actually make calls to the database in your unit tests.

The simple technique behind this code is described in this blog post by Fabian Schmengler. Basically, it involves taking advantage of PHP's namespace resolution rules.

Install

Via Composer

$ composer require jeremeamia/func-mocker

Usage

Let's you have a RandomNumberGenerator class in the namespace, My\App, that calls the global function rand(). You could overwrite the usage of rand() for that particular namespace by using FuncMocker.

use My\App\RandomNumberGenerator;
use FuncMocker\Mocker;

Mocker::mock('rand', 'My\App', function () {
    return 5;
});

$rng = new RandomNumberGenerator(1, 10);
echo $rng->getNumber();
//> 5
echo $rng->getNumber();
//> 5
echo $rng->getNumber();
//> 5

Longer Example

Assume there is a class that uses the global function (e.g., time()) that you'd like to mock.

<?php

namespace My\Crypto;

use Psr\Http\Message\RequestInterface as Request;

class Signer
{
    // ...

    public function getStringToSign(Request $request)
    {
        return $request->getMethod() . "\n"
            . time() . "\n"
            . $request->getHeader('X-API-Operation')[0] . "\n"
            . $request->getBody();            
    }
    
    // ...
}

Here is an example of a PHPUnit test that uses FuncMocker to mock time() to return a fixed value, making it much easier to write a test.

<?php

namespace My\App\Tests;

use FuncMocker\Mocker as FuncMocker;
use My\Crypto\Signer;
use Psr\Http\Message\RequestInterface as Request;

class SignerTest extends \PHPUnit_Framework_TestCase
{
    // ...

    public function testCanGetStringToSign()
    {
        // Mock the request with PHPUnit
        $request = $this->getMock(Request::class);
        $request->method('getMethod')->willReturn('POST');
        $request->method('getHeader')->willReturn(['CREATE_THING']);
        $request->method('getBody')->willReturn('PARAMS');
        
        // Mock the call to PHP's time() function to give us a deterministic value.
        FuncMocker::mock('time', 'My\Crypto', function () {
            return 12345;
        });
                
        $signer = new Signer();
        
        // Check to see that the string to sign is constructed how we would expect.
        $this->assertEquals(
            "POST\n12345\nCREATE_THING\nPARAMS",
            $signer->getStringToSign()
        );
    }
    
    // ...
}

Disabling and Re-Enabling

FuncMocker also lets you disable mocks you've setup, in case you need the function to behave normally in your some of your tests.

$func = FuncMocker\Mocker::mock('time()', 'My\App', function () {
    return 1234567890;
});

echo My\App\time();
//> 1234567890

$func->disable();
echo My\App\time();
//> 1458018866

$func->enable();
echo My\App\time();
// > 1234567890

Limitations

1. The function to be mocked must be used in a namespace other than the global namespace.
2. The function to be mocked must not be referenced using a fully-qualified name (e.g., \time()).

Testing

$ composer test

Credits

• Jeremy Lindblom - Main author.
• Marius Sarca - Borrowed his stream wrapper include technique from opis/closure.

Alternatives

• Do it yourself. See the following articles:
  • Fabian Schmengler's Blog - "Mocking" built-in functions like time() in Unit Tests
  • Matthew Weier O'Phinney's Blog - Testing Code That Emits Output
• php-mock/php-mock - Similar function mocking library I found afterwards.
• Patchwork - More robust mocking library that can intercept calls to functions.
• Atoum - Fullf-featured test framework with function mocking included.

License

The MIT License (MIT). Please see License File for more information.