Cannot select elements inside "auto-binding" template - polymer

Question

I have created some custom elements, now I'm writing tests for them.
I wanted to use "auto-binding" because I have plenty of attributes that needs to be bound among my elements.
Unfortunately I cannot query any element inside the template.
Here is some code.
<template id="root" is="auto-binding">
<dalilak-data-service id="dds" regions="{{regions}}"></dalilak-data-service>
<dalilak-regions-handler id="drh" regions="{{regions}}" flattendedRegions="{{flattendRegions}}" descendantsRegionNames="{{descendantsRegionNames}}" regionsByNameId="{{regionsByNameId}}"></dalilak-regions-handler>
</template>
In the test script I have tried the following
drh = document.querySelector('#drh');
suite('dalilak-regions-handler', function() {
test('handler initialized', function() {
assert.ok(drh);
});
});
Also tried this:
drh = document.querySelector('* /deep/ #drh'); // or '#root /deep/ #drh'
suite('dalilak-regions-handler', function() {
test('handler initialized', function() {
assert.ok(drh);
});
});
But none of them worked.
Note without the template I can query my custom elements.

Answer 1

auto-binding templates stamp asynchronously, I expect your problem is that you need to wait for the template to stamp before querying for elements.
The template fires a template-bound event when this happens, so you can use code like this:
addEventListener('template-bound', function() {
drh = document.querySelector('#drh');
...
});
Of course, this means your testing infrastructure will need to understand how to handle asynchrony, which can be a concern.

Answer 2

Where possible, it is best to avoid the /deep/ selector. That is a nuclear option and can return unexpected results because it pierces all shadow DOMs. It also won't work for your auto-binding template because its contents are inside a #document-fragment, not a #shadow-root. Instead, try querying the #document-fragment itself. This preferable because you are limiting your query to the scope of your template, which is much more precise.
var template = document.querySelector('#root');
var drh = template.content.querySelector('#drh');