PHPUnit: mock an iterator

UnitTestCase.php

<?php

namespace Tests;

use ArrayIterator;
use PHPUnit\Framework\MockObject\MockObject;
use PHPUnit\Framework\TestCase;

class UnitTestCase extends TestCase
{
    /**
     * Asserts that the given callback throws the given exception.
     *
     * @param string $expectClass The name of the expected exception class
     * @param callable $callback A callback which should throw the exception
     */
    protected function assertException(string $expectClass, callable $callback)
    {
        try {
            $callback();
        } catch (\Throwable $exception) {
            $this->assertInstanceOf($expectClass, $exception, 'An invalid exception was thrown');
            return;
        }

        $this->fail('No exception was thrown');
    }

    /**
     * For when you need to mock an iterator withing a method.
     *
     * @param MockObject $mockIterator
     * @param array $items
     * @return MockObject
     */
    protected function mockIterator(MockObject $mockIterator, array $items = []): MockObject
    {
        $iterator = new ArrayIterator($items);

        $mockIterator
            ->method('rewind')
            ->willReturnCallback(function () use ($iterator): void {
                $iterator->rewind();
            });

        $mockIterator
            ->method('current')
            ->willReturnCallback(function () use ($iterator) {
                return $iterator->current();
            });

        $mockIterator
            ->method('key')
            ->willReturnCallback(function () use ($iterator) {
                return $iterator->key();
            });

        $mockIterator
            ->method('next')
            ->willReturnCallback(function () use ($iterator): void {
                $iterator->next();
            });

        $mockIterator
            ->method('valid')
            ->willReturnCallback(function () use ($iterator): bool {
                return $iterator->valid();
            });

        return $mockIterator;
    }
}