PHPUnit best practices to organize tests

I'll start of by linking to the manual and then going into what I've seen and heard in the field.

Organizing phpunit test suites

Module / Test folder organization in the file system

My recommended approach is combining the file system with an xml config.

tests/
 \ unit/
 | - module1
 | - module2
 - integration/
 - functional/

with a phpunit.xml with a simple:

<testsuites>
  <testsuite name="My whole project">
    <directory>tests</directory>
  </testsuite>
</testsuites>

you can split the testsuites if you want to but thats a project to project choice.

Running phpunit will then execute ALL tests and running phpunit tests/unit/module1 will run all tests of module1.

Organization of the "unit" folder

The most common approach here is to mirror your source/ directory structure in your tests/unit/ folder structure.

You have one TestClass per ProductionClass anyways so it's a good approach in my book.

In file organization

One class per file.

It's not going to work anyways if you have more than one test class in one file so avoid that pitfall.

Don't have a test namespace

It just makes writing the test more verbose as you need an additional use statement so I'd say the testClass should go in the same namespace as the production class but that is nothing PHPUnit forces you to do. I've just found it to be easier with no drawbacks.

Executing only a few tests

For example phpunit --filter Factory executes all FactoryTests while phpunit tests/unit/logger/ executes everything logging related.

You can use @group tags for something like issue numbers, stories or something but for "modules" I'd use the folder layout.

Multiple xml files

It can be useful to create multiple xml files if you want to have:

one without code coverage
one just for the unit tests (but not for the functional or integration or long running tests)
other common "filter" cases
PHPBB3 for example does that for their phpunit.xmls

Code coverage for your tests

As it is related to starting a new project with tests:

My suggestion is to use @covers tags like described in my blog (Only for unit tests, always cover all non public functions, always use covers tags.
Don't generate coverage for your integration tests. It gives you a false sense of security.
Always use whitelisting to include all of your production code so the numbers don't lie to you!

Autoloading and bootstrapping your tests

You don't need any sort of auto loading for your tests. PHPUnit will take care of that.

Use the <phpunit bootstrap="file"> attribute to specify your test bootstrap. tests/bootstrap.php is a nice place to put it. There you can set up your applications autoloader and so on (or call your applications bootstrap for that matter).

Summary

Use the xml configuration for pretty much everything
Seperate unit and integration tests
Your unit test folders should mirror your applications folder structure
To only execute specif tests use phpunit --filter or phpunit tests/unit/module1
Use the strict mode from the get go and never turn it off.

Sample projects to look at

Sebastian Bergmanns "Bank Account" example project
phpBB3 Even so they have to fight some with their legacy ;)
Symfony2
Doctrine2

Basic Directory Structure:

I have been experimenting with keeping the test code right next to the code being tested, literally in the same directory with a slightly different file name from the file with the code it is testing. So far I am liking this approach. The idea is you don't have to spend time and energy keeping the directory structure in sync between your code and your test code. So if you change the name of the directory the code is in, you don't then also need to go and find and change the directory name for the test code. This also causes you to spend less time looking for the test code that goes with some code as it is right there next to it. This even makes it less of a hassle to create the file with the test code to begin with because you don't have to first find the directory with the tests, possibly create a new directory to match the one you are creating tests for, and then create the test file. You just create the test file right there.

One huge advantage of this is it means the other employees (not you because you would never do this) will be less likely to avoid writing test code to begin with because it is just too much work. Even as they add methods to existing classes they will be less likely to not feel like adding tests to the existing test code, because of the low friction of finding the test code.

One disadvantage is this makes it harder to release your production code without the tests accompanying it. Although if you use strict naming conventions it still might be possible. For example, I have been using ClassName.php, ClassNameUnitTest.php, and ClassNameIntegrationTest.php. When I want to run all the unit tests, there is a suite that looks for files ending in UnitTest.php. The integration test suite works similarly. If I wanted to, I could use a similar technique to prevent the tests from getting released to production.

Another disadvantage of this approach is when you are just looking for actual code, not test code, it takes a little more effort to differentiate between the two. But I feel this is actually a good thing as it forces us to feel the pain of the reality that test code is code too, it adds its' own maintenance costs, and is just as vitally a part of the code as anything else, not just something off to the side somewhere.

One test class per class:

This is far from experimental for most programmers, but it is for me. I am experimenting with only having one test class per class being tested. In the past I had an entire directory for each class being tested and then I had several classes inside that directory. Each test class setup the class being tested in a certain way, and then had a bunch of methods each one with a different assertion made. But then I started noticing certain conditions I would get these objects into had stuff in common with other conditions it got into from other test classes. The duplication become too much to handle, so I started creating abstractions to remove it. The test code became very difficult to understand and maintain. I realized this, but I couldn't see an alternative that made sense to me. Just having one test class per class seemed like it would not be able to test nearly enough situations without becoming overwhelming to have all that test code inside one test class. Now I have a different perspective on it. Even if I was right, this is a huge dampener on other programmers, and myself, wanting to write and maintain the tests. Now I am experimenting with forcing myself to have one test class per class being tested. If I run into too many things to test in that one test class, I am experimenting with seeing this as an indication that the class being tested is doing too much, and should be broken up into multiple classes. For removing duplication I am trying to stick to simpler abstractions as much as possible that allows everything to exist in one readable test class.

UPDATE I am still using and liking this approach, but I have found a very good technique for reducing the amount of test code and the amount of duplication. It is important to write reusable assertion methods inside the test class itself that gets heavily used by the test methods in that class. It helps me to come up with the right types of assertion methods if I think of them as internal DSLs (something Uncle Bob promotes, well actually he promotes actually making internal DSLs). Sometimes you can take this DSL concept even further (actually make a DSL) by accepting a string parameter that has a simple value that refers to what kind of test you are trying to perform. For example, one time I made a reusable asssertion method that accepted a $left, $comparesAs, and a $right parameter. This made the tests very short and readable as the code read something like $this->assertCmp('a', '<', 'b').

Honestly, I can't emphasize that point enough, it is the entire foundation of making writing tests something that is sustainable (that you and the other programmers want to keep doing). It makes it possible for the value that tests add to outweigh what they take away. The point is not that you need to use that exact technique, the point is you need to use some kind of reusable abstractions that allow you to write short and readable tests. It might seem like I'm getting off topic from the question, but I'm really not. If you don't do this, you will eventually fall into the trap of needing to create multiple test classes per class being tested, and things really break down from there.