ORM 'or_where' use

I'd like my ORM factory to return records where x = 1 and y is either equal to 1 or 2. I've tried a few variations with and_where, but it returns loads more than records than it should. The ORM is then stored in a php variable. Here's my current code

$tests = ORM::factory('Test')
    ->where('x', '=', 1)
    ->or_where('y', '=', 1)
    ->or_where('y', '=', 2)
    ->find_all();

You can group the OR statements via and_where_open()/and_where_close() like so (untested)

$test = ORM::factory('Test')
    ->where('x', '=', 1)     // 1
    ->and_where_open()       // 2
    ->where('y', '=', 1)     // 3
    ->or_where('y', '=', 2)  // 4
    ->and_where_close()
    ->find_all();

This should create a query like

SELECT .. FROM .. WHERE x = 1   AND (  y=1   OR y=2  )
                        ^^^^^   ^^^^^  ^^^   ^^^^^^
                          1       2     3      4