I'm having trouble writing a Symfony 2 functional test to set checkboxes that are part of an array (i.e. a multiple and expanded select widget)

In the documentation the example is

$form['registration[interests]']->select(array('symfony', 'cookies'));

But it doesn't show what html that will work with and it doesn't work with mine. Here is a cutdown version of my form

<form class="proxy" action="/proxy/13/update" method="post" >
    <input type="checkbox" id="niwa_pictbundle_proxytype_chronologyControls_1" name="niwa_pictbundle_proxytype[chronologyControls][]" value="1" />

    <input type="checkbox" id="niwa_pictbundle_proxytype_chronologyControls_2" name="niwa_pictbundle_proxytype[chronologyControls][]" value="2" />

    <input type="checkbox" id="niwa_pictbundle_proxytype_chronologyControls_3" name="niwa_pictbundle_proxytype[chronologyControls][]" value="3" />
</form>

Once it get it working there I'm going to move on to a manually made form

<input type="checkbox" id="13" name="proxyIDs[]" value="13">
<input type="checkbox" id="14" name="proxyIDs[]" value="14">
<input type="checkbox" id="15" name="proxyIDs[]" value="15">

I have tried things like 

$form = $crawler->selectButton('Save')->form();
$form['niwa_pictbundle_proxytype[chronologyControls]']->select(array('3'));
$form['niwa_pictbundle_proxytype[chronologyControls][]']->select(array('3'));

but the first fails saying select is being run on a non-object and the second says Unreachable field "".

symfony functional-testing
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