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Testing PHP Apps with Peridot

Posted on 03 Apr 2015

Pretty much everyone agrees that you should be testing your applications, libraries, frameworks, etc, in some way or another.

Sure, there are valid times not to test, like when working on a proof of concept or with an unknown market, but those times are pretty few and far between. And if that app actually takes off, you should either rewrite it from scratch with tests, or get tests written for it ASAP.

In PHP Land, PHPUnit has pretty much dominated the scene. It’s been around forever, and nearly every major project uses it.

I’ve been using PHPUnit for awhile now, simply because that’s what PHP projects use. I’ve never given it much thought, even though at times, it’s been exceedingly frustrating to use, especially when dealing with mock objects.

On the Behavior-Driven Development (BDD) front, the big name is Behat, and other players, like phpspec have existed for awhile.

I’ve used Behat a bit, but it always felt alien and awkward to me. It just didn’t feel right. And while I haven’t tried it, phpspec looks much the same: just awkward.

Enter Peridot.


Peridot is a spec-based, BDD testing framework. Writing tests has never felt so freeing. It just feels right.

If you’ve ever used Jasmine for JavaScript testing or RSpec for Ruby testing, Peridot will feel very familiar.

Peridot’s Approach

Specs in Peridot look something like this:


describe('Maths', function () {
  describe('addition', function () {
    context('when the numbers are negative', function () {
      it('should generate a negative sum', function () {
        expect(-5 + -5)->to->equal(-10);

    context('when the numbers are positive', function () {
      it('should generate a positive sum', function () {
        expect(5 + 5)->to->equal(10);

These describe and context blocks can nest as deep as you need them to go. This ends up giving you some very helpful output when running your specs:

$ ./vendor/bin/peridot foo.spec.php

      when the numbers are negative
        ✓ should generate a negative sum
      when the numbers are positive
        ✓ should generate a positive sum

  2 passing (3 ms)

The output is even gorgeous and expressive. But if you’re missing the simple dots from PHPUnit, you can drop in a different output reporter.

Next Level Assertions with Leo

The Peridot project also supplies an assert library, called Leo. I’ve used this in the examples above:


expect(5 + 5)->to->equal(10);

Leo also comes with an assert library, if you prefer that format of testing:


$assert = new Assert();
$assert->typeOf('string', 'hello', 'is string');
$assert->operator(5, '<', 6, 'should be less than');
$assert->throws(function() {
    throw new Exception('exception');
}, 'Exception');

Leo supports a pretty expansive matcher library, with a plugin system for adding additional matchers.

Checkout the HTTP Foundation plugin for Leo, which makes testing Symfony-based applications incredibly easy:


expect($response)->to->allow(['POST', 'GET']);


One of the biggest wins for using Peridot is the concurrency plugin, which allows you to run your slow tests concurrently to get the results faster.

This is great if you have a large, functional test suite that takes forever to run. It’s quite literally a game changer.


Peridot is awesome because of its event based architecture and its awesome plugin system.

If Peridot doesn’t do something you want it to do, you can simply write a plugin to extend the functionality.

My favorite plugin is the watcher plugin, which automatically re-runs your tests whenever the code changes. Now I know immediately when I’ve screwed something up!

More Information

If you want to learn more information about Peridot, checkout their website. You can also checkout the slides on talks the developers gave at GrPhpDev:

Full Disclosure

For the sake of full disclosure, I should probably point out that I work with the two developers who wrote Peridot. That doesn’t change how epically awesome it is though. Check it out!


The Clean Architecture in PHP

I've written a book on the Clean Architecture in PHP, which covers how to cleanly organize and decouple your code in a way that prepares it to survive and be easy to maintain for the long term.

Check it out!