Collections\Tests\Dictionary\KeysTest::test_keys PHP Method

    public function test_keys()
    {
        $d = (new Dictionary('string', 'int'))->add('a', 1)->add('b', 2)->add('c', 3)->add('d', 4);
        $result = $d->keys();
        $expected = ['a', 'b', 'c', 'd'];
        $this->assertEquals($expected, $result);
    }