Prime Factors Kata - https://laracasts.com/series/code-katas-with-phpunit/episodes/2

PrimeFactors.php

<?php

namespace App;

class PrimeFactors
{
    public function generate($number)
    {
        $factors = [];

        for ($divisor = 2; $number > 1; $divisor++) {
            for (; $number % $divisor === 0; $number /= $divisor) {
                $factors[] = $divisor;
            }
        }

        return $factors;
    }
}

PrimeFactorsTest.php

<?php

use App\PrimeFactors;

class PrimeFactorsTest extends \PHPUnit\Framework\TestCase
{
    /**
     * @test
     * @dataProvider factors
     */
    function it_generates_prime_factors($number, $expected)
    {
        $factors = new PrimeFactors();

        $this->assertEquals($expected, $factors->generate($number));
    }

    public function factors()
    {
        return [
            [1, []],
            [2, [2]],
            [3, [3]],
            [4, [2, 2]],
            [5, [5]],
            [6, [2, 3]],
            [7, [7]],
            [8, [2, 2, 2]],
            [9, [3, 3]],
            [11, [11]],
            [12, [2, 2, 3]],
            [17, [17]],
            [100, [2, 2, 5, 5]]
        ];
    }

}