用 Mockery mock IteratorAggregate 讓 foreach 正常運作

在開發 Google Firebase 相關程式時，需要 mock QuerySnapshot，而它 implement 了 IteratorAggregate，直接用 Mockery mock 會不知道怎麼讓 foreach 跑起來。

IteratorAggregate 是什麼

IteratorAggregate 是 PHP 內建的 interface，只要 implement 它並實作 getIterator()，物件就可以用 foreach 迭代。getIterator() 要回傳一個 Traversable，foreach 實際上是對它迭代：

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class myData implements IteratorAggregate {
    public $property1 = "Public property one";
    public $property2 = "Public property two";
    public $property3 = "Public property three";

    public function __construct() {
        $this->property4 = "last property";
    }

    public function getIterator() {
        return new ArrayIterator($this);
    }
}

$obj = new myData;

foreach($obj as $key => $value) {
    var_dump($key, $value);
    echo "\n";
}

Mock 的方式

只要 mock getIterator() 回傳 ArrayObject 就行了：

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composer require --dev mockery/mockery

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use ArrayObject;
use IteratorAggregate;
use Mockery;
use PHPUnit\Framework\TestCase;

class IteratorAggregateTest extends TestCase
{
    public function test_mock_aggregate(): void
    {
        $iterator = Mockery::mock(IteratorAggregate::class);
        $iterator->allows('getIterator')
          ->andReturn(new ArrayObject(['foo', 'bar']));

        foreach ($iterator as $value) {
            echo $value."\n";
        }
    }
}

三個條件就夠了：class implement IteratorAggregate、mock getIterator、return ArrayObject。