cannot pre-hook to set multiple choices values for checkboxes

[Alluryck]

field1 and field2 are textfield, field3 is a checkboxes field:

$hook->setValue('field1','john@email.net');
$hook->setValue('field2','John Doe');
$hook->setValue('field3','music||films||books');
return true;

It does not set checkboxes for field3.

Also tried with:
$hook->setValue('field12',json_encode(array('music','films','books')));

Would be great to be able to dynamically pass checkboxes arrays.