如何测试使用cache变量的方法？

Question

<?php

use yii\db\ActiveRecord;

class Model extends ActiveRecord
{
    protected static $ids = [];

    public static function getIds()
    {
        if (empty(static::$ids)) {
            static::$ids = static::find()->select('id')->column();
        }

        return static::$ids;
    }
}

How to use the test to make sure that the query is executed once by repeatedly calling this method ?

Preferably using codeception or phpunit.

Answer 1

Tests are not just a way to ensure your code works, they also help identify code smells. In your case writing a test is hard, because you use static methods.

There used to be a staticExpects method but that was deprecated in phpunit long ago, so that's not really feasible. The best way to make this code testable is to remove the static keyword. This is easy for getIds() but since the static find() is defined by a 3rd party (yii's ActiveRecord) you can't really remove it. Instead you could wrap it in a non-static method. This gives you the benefit of being able to move away from the Active Record to some other implementation like Doctrine in the future, by just touching these small methods wrapping the 3rd party code.

Once you do this you could create a partial mock of your model to make sure that method is called:

class Model extends ActiveRecord
{
    private $ids;

    protected function findIds()
    {
        return static::find()->select('id')->column();
    }

    public function getIds()
    {
        if (empty($this->ids)) {
            $this->ids = $this->findIds()
        }

        return $this->ids;
    }
}

and in your test:

public function testFindIdsIsCalledWhenGetterIsNotInitialized()
{
    $model = $this->getMockBuilder(Model::class)
        ->setMethods(['findIds'])
        ->getMock();
    $model->expects($this->once())
        ->method('findIds')
        ->will($this->returnValue([1, 2, 3]));

    $ids = $model->getIds();

    $this->assertEquals([1, 2, 3], $ids);
}

This should have 2 assertions, one for the expected method call and one for the returned values. This test bypasses the Active Record and only ensures that your getIds() method works as expected. Another way to approach this is, as mentioned in the comments to your question, to use a functional test that actually tests the database interactions by fetching the data from a (test) database. Obviously since this requires having a database connection and retrieving test data, eg from some previously setup fixtures, it's a bit more work and the test will be slower. Depending on how big your project is that might not be an issue and you might feel more comfortable testing the logic in the Active Record implementation as well.