MathPHP\SetTheory\SetTest::testIteratorInterface PHP Method

    public function testIteratorInterface()
    {
        $set = new Set([1, 2, 3, 4, 5]);
        $i = 1;
        foreach ($set as $key => $value) {
            $this->assertEquals($i, $key);
            $this->assertEquals($i, $value);
            $i++;
        }
        $set = new Set([new Set([1, 2]), new Set([3, 4])]);
        $i = 1;
        foreach ($set as $key => $value) {
            if ($i === 1) {
                $this->assertEquals('Set{1, 2}', $key);
                $this->assertEquals(new Set([1, 2]), $value);
            }
            if ($i === 2) {
                $this->assertEquals('Set{3, 4}', $key);
                $this->assertEquals(new Set([3, 4]), $value);
            }
            $i++;
        }
    }