Unit testing in PHP
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The document discusses advantages and techniques for unit testing PHP code. Key advantages include tests running faster than manual testing, preventing recurring bugs, and finding bugs before users. Challenges include needing to write tests to see benefits and difficulty retrofitting tests for existing code. The document provides guidance on writing simple, isolated tests and describes common PHPUnit methods and patterns for testing. It also discusses how to address inherently hard to test code structures and writes testable code through practices like dependency injection.
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Unit testing in PHP
- 1. Unit Testing in PHP Lee Boynton
- 2. Advantages to Automating Testing ¡ñ Faster to test ¡ð Don't need to "click about" ¡ð Don't need to login ¡ð Don't need to have commented out test code ¡ñ Prevent recurring bugs ¡ð Write a test for bug, run the test after every change ¡ñ Easier to test edge cases ¡ñ Less fear when making changes ¡ð You may have forgotten how the code works ¡ð You may inherit someone else's code ¡ñ Find bugs before your users ¡ð This means you keep your customers happy, this means more money!
- 3. Advantages to Automating Testing ¡ñ Better designed code, especially with TDD ¡ð Unit tested code tends to be ¡ö Less coupled ¡ö Less complex ¡ñ Tests document how code should work ¡ñ Once you are good at unit testing, it's probably faster ¡ñ Tests don't have to be amazing: "Imperfect tests, run frequently, are much better than perfect tests that are never written at all"
- 4. Disadvantages ¡ñ You have to suck it up and write tests to really see the benefits ¡ñ Hard to retrofit tests ¡ð You may have to refactor old code, or ¡ð You may have to write a lot of test code for code which is not easy to test ¡ñ Harder to write bad code ¡ñ You probably won't want to write code without tests again
- 5. Goals When Writing Tests ¡ñ Tests should be ¡ð Simple ¡ö Don't have ifs or loops ¡ð Easy to write ¡ð Easy to read ¡ð Easy to run ¡ð Isolated ¡ñ But these ideas may conflict or be hard to achieve ¡ð Do your best ¡ð Can improve tests over time ¡ð Bad tests better than no tests
- 6. Common PHPUnit Methods ¡ñ $this->assertTrue($value, 'Value should have been true') ¡ñ $this->assertFalse($value, 'Value should have been false') ¡ñ $this->assertEquals($expected, $actual, 'The result is not what was expected') ¡ñ Try to write a message to indicate what specifically is being asserted ¡ð Easier to understand what's wrong instead of e.g. "Failed asserting that false is true"
- 7. Common PHPUnit Patterns ¡ñ Use setUp() method to instantiate the class you are testing ¡ð This works well if you don't have lots of constructor parameters ¡ñ Use data providers to test lots of different inputs ¡ð Tests shouldn't have duplicate code either ¡ñ Use tearDown() method if you need to clean up external resources after each test is run ¡ð Files ¡ð Database
- 8. Hard to Test Things ¡ñ Static calls to other classes ¡ð You cannot mock the dependency ¡ñ Singletons ¡ð Constructor is private or protected ¡ð Uses static call to get instance ¡ð Cannot guarantee there are no side effects when running multiple tests ¡ñ Private methods ¡ð Usually you indirectly test these when you test public methods ¡ð Can use reflection if you really want, but this probably means you should refactor
- 9. Hard to Test Things ¡ñ Hard coded dependencies ¡ð Such as when a class instantiates another class ¡ñ Magic methods ¡ð __call ¡ð __get ¡ð __set
- 10. How to Write Testable Code ¡ñ Use dependency injection ¡ð This means you don't instantiate classes unless you're in a factory ¡ñ Keep methods relatively small ¡ñ Avoid having lots of private methods ¡ñ Write classes which do one thing (single responsibility principle)
- 11. Go go go! ¡ñ http://www.phpunit. de/manual/current/en/index.html