I believe changing your operator to ‘AND’ like below will work:
$selectedOptions = array('test-attribute', 'test3');
$args=array(
'post_type' => 'product',
'post_status' => 'publish',
'posts_per_page' => -1,
'tax_query' => array(
array(
'taxonomy' => 'pa_filterable-attribute',
'terms' => $selectedOptions,
'field' => 'slug',
'operator' => 'AND'
)
)
);