PHPUnit: Using a data provider that returns an Iterator object

Question

I was reading documentation of PHPUnit. I'm stuck on Example 2.7 & Example 2.8. It's showing two errors.

1. PHP Warning: fopen(data.csv): failed to open stream: No such file or directory
2. The data provider specified for DataTest::testAdd is invalid. TypeError: fclose() expects parameter 1 to be resource, bool given

Below code of CsvFileIterator class

<?php declare(strict_types=1);
use PHPUnit\Framework\TestCase;

final class CsvFileIterator implements Iterator
{
    private $file;
    private $key = 0;
    private $current;

    public function __construct(string $file)
    {
        $this->file = fopen($file, 'r');
    }

    public function __destruct()
    {
        fclose($this->file);
    }

    public function rewind(): void
    {
        rewind($this->file);

        $this->current = fgetcsv($this->file);
        $this->key     = 0;
    }

    public function valid(): bool
    {
        return !feof($this->file);
    }

    public function key(): int
    {
        return $this->key;
    }

    public function current(): array
    {
        return $this->current;
    }

    public function next(): void
    {
        $this->current = fgetcsv($this->file);

        $this->key++;
    }
}

Below code of DataTest class

<?php declare(strict_types=1);
use PHPUnit\Framework\TestCase;
require "CsvFileIterator.php";

final class DataTest extends TestCase
{
    /**
     * @dataProvider additionProvider
     */
    public function testAdd(int $a, int $b, int $expected): void
    {
        $this->assertSame($expected, $a + $b);
    }

    public function additionProvider(): CsvFileIterator
    {
        return new CsvFileIterator('data.csv');
    }
}

Below sample data.csv

0, 0, 0
0, 0, 0
0, 0, 0

Please help me to figure out, what I'm doing wrong. Thanks in advance.

Note: My local is windows 10.