iter\IterTest::testComplexReductions PHP Method

    public function testComplexReductions()
    {
        $this->assertSame(['ab', 'abcd', 'abcdef'], toArrayWithKeys(reductions(function ($acc, $value, $key) {
            return $acc . $key . $value;
        }, ['a' => 'b', 'c' => 'd', 'e' => 'f'], '')));
    }