Our First Test

We already have this Dinosaur class... and it's pretty simple. But when it comes to dinosaurs, bugs in our code can be, mmm, a bit painful. So let's add some basic tests!

Creating the Test Class

Mmmm... where do we put this new test? We can technically put our tests anywhere within our project. But when we installed symfony/test-pack, Flex created a tests/ directory which, no surprise, is the recommended place to put our tests.

Remember that, in this tutorial, we're only dealing with Unit tests. So, inside of tests/, create a new directory called Unit. And because our Dinosaur::class lives in the Entity namespace - create an Entity directory inside of that at the same time.

All of this organization is technically optional: you can organize the tests/ directory however you want. But, putting all of our unit tests into a Unit directory is just... nice. And the reason we made the Entity directory is because we want the file structure inside of Unit to mirror our src/ directory structure. That's a best practice that keeps our tests organized.

Finally, create a new class called DinosaurTest. Using that Test suffix makes sense: we're testing Dinosaur, so we call this DinosaurTest! But it's also a requirement: PHPUnit - our testing library - requires this. It also requires that each class extend TestCase:

Now let's go ahead and write a simple test to make sure everything is working.

Inside our DinosaurTest class, let's add public function testIsWorks()... where we'll create the most exciting test ever! If you like return types - I do! - use void... though that's optional

Inside call self::assertEquals(42, 42):

That's it! It's not a very interesting test - if our computer thinks that 42 doesn't equal 42, we have bigger problems - but it's enough.

Executing PHPUnit

How do we execute the test? By executing PHPUnit. At your terminal, run:

./vendor/bin/phpunit

And... awesome! PHPUnit saw one test - for our one test method - and one assertion.

We could also say bin/phpunit to execute our tests, which is basically just a shortcut to run vendor/bin/phpunit.

But, I'm sure your curious... What's... an assertion?

Looking back at DinosaurTest, the one assertion refers to the assertEquals() method, which comes from PHPUnit's TestCase class. If the actual value - 42 - doesn't match the expected value, the test would fail. PHPUnit has a bunch more assertion methods... and we can see them all by going to https://phpunit.readthedocs.io. This is full of goodies, including an "Assertions" section. And... wow! Look at them all... We'll talk about the most important assertions throughout the series. But for now, back to the test!

Test Naming Conventions

Because, I have a question: how did PHPUnit know that this is a test? When we call vendor/bin/phpunit, PHPUnit does three things. First, it looks for its configuration file, which is phpunit.xml.dist:

Inside, it finds testsuites... and the directory part says:

Hey PHPUnit: go look inside a tests/ directory for tests!

Second, it finds that directory and recursively looks for every class that ends with the word Test. In this case, DinosaurTest. Finally, once it finds a test class, it gets a list of all of its public methods.

So... am I saying that PHPUnit will execute every public method as a test? Let's find out! Create a new public function itWorksTheSame(): void

Inside we are going to self::assertSame() that 42 is equal to 42. assertSame() is very similar to assertEquals() and we'll see the difference in a minute.

Now, move back to your terminal and let's run these tests again:

./vendor/bin/phpunit

Huh? PHPUnit still says just one test and one assertion. But inside our test class, we have two tests and two assertions. The problem is that PHPUnit only executes public methods that are prefixed with the word test. You could put the @test annotation above the method, but that's not very common. So let's avoid being weird, and change this to testItWorksTheSame().

Now when we run the test:

./vendor/bin/phpunit

PHPUnit sees 2 tests and 2 assertions! Shweeeet!

Testing Failures 😱

What does it look like when a test fails? Let's find out! Change our expected 42 to a string inside testItWorks()... and do the same inside testItWorksTheSame(). Yup, one of these won't work.

This time when we try it:

./vendor/bin/phpunit

Oh no! One failure!

DinosaurTest::testItWorksTheSame() failed asserting that 42 is identical to 42.

So... assertEquals() passed, but assertSame() failed. That's because assertEquals() is the equivalent to doing an if 42 == 42: using the double equal sign. But assertSame() is equivalent to 42 === 42: with three equal signs.

And since the string 42 does not triple-equals the integer 42, that test fails and PHPUnit yells at us.

Ok, we've got our first tests behind us! Though... testing that the answer to life the universe and everything is equal to the answer to life the universe and everything... isn't very interesting. So next: let's write real tests for the Dinosaur class.