5 Steps to Your First Fixer or Sniff Test

2018-04-16

When I wrote my first Sniff 4 years ago I wanted to test it. I expected testing class, that would register sniff, provide ugly code and compare it to fixed one. So I started to explore PHP_CodeSniffer looking for such feature. Found one class, second class, warnings, errors, uff and after 10th error, I closed it.

When I wrote my first Fixer, the story was a bit shorter but very similar. No wonder people don't test when the entry barrier is so huge.

Since I use both of them and I want to motivate people to write their own sniffs and fixers, I turned this barrier to just 5 short steps for both of them.

Imagine you have a LowerBoolConstantsFixer that fixes all uppercase bool constants to lowercase ones:

-$value = TRUE;
+$value = true;

And nothing more. How do we take this test case to PHPUnit? That is what ECS Tester package will help us with.

1. Install the package

composer require symplify/easy-coding-standard-tester --dev

2. Create a config with checker(s) you want to test

# /tests/Fixer/LowerBoolConstantsFixer/config.yml
services:
    Your\CodingStandard\LowerBoolConstantsFixer: ~

(Checker is a group name for sniff and fixer, nothing more.)

3. Create a Test Case and Provide the Config

Create a test case that extends Symplify\EasyCodingStandardTester\Testing\AbstractCheckerTestCase class.

<?php declare(strict_types=1);

namespace Your\CodingStandard\Tests\LowerBoolConstantsFixer;

use Symplify\EasyCodingStandardTester\Testing\AbstractCheckerTestCase;

final class LowerBoolConstantsFixerTest extends AbstractCheckerTestCase
{
    // ...
}

And provide the config above in provideConfig() method.

Try to keep this standard in every test to reduce the maintenance of the test, e.g. __DIR__ . '/config.yml'.
You can also make configured test of the same checker, __DIR__ . '/configured-config.yml'.

 <?php declare(strict_types=1);

 namespace Your\CodingStandard\Tests\LowerBoolConstantsFixer;

 use Symplify\EasyCodingStandardTester\Testing\AbstractCheckerTestCase;

 final class LowerBoolConstantsFixerTest extends AbstractCheckerTestCase
 {
     // ...

+    protected function provideConfig(): string
+    {
+        return __DIR__ . '/config.yml';
+    }
 }

4. Test The Checker Behavior

You can make use of 3 testing methods:

doTestCorrectFile($correctFile) - the file should not be affected by this checker
doTestWrongToFixedFile($wrongFile, $fixedFile) - classic before/after testing
doTestWrongFile($wrongFile) - only for sniff - it doesn't fix, just reports

<?php declare(strict_types=1);

namespace Your\CodingStandard\Tests\LowerBoolConstantsFixer;

use Symplify\EasyCodingStandardTester\Testing\AbstractCheckerTestCase;

final class LowerBoolConstantsFixerTest extends AbstractCheckerTestCase
{
    public function test(): void
    {
        $this->doTestCorrectFile(__DIR__ . '/correct/correct.php.inc');

        $this->doTestWrongToFixedFile(
            __DIR__ . '/wrong/wrong.php.inc',
            __DIR__ . '/fixed/fixed.php.inc'
        );
    }

    protected function provideConfig(): string
    {
        return __DIR__ . '/config.yml';
    }
}

5. The Best For Last - Create the Code Snippets

This part you enjoy the most because your job is to break the checker... well, at least verify it behaves as you want it to behave.

What should it skip? Well, since NULL / null is not a bool value...

// correct/correct.php.inc
$value = NULL;
$value = null;

I guess you already know the before/after part:

// wrong/wrong.php.inc
$value = TRUE;
$value = FALSE;

// fixed/fixed.php.inc
$value = true;
$value = false;

That's it!

Now you know all you need to be able to test any fixer or sniff. But if you want to know more, check the ECS Tester README.

Enjoy simple testing!

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