Multiple polymer element tests with karma test runner

Question

I have written a few tests for polymer elements in jasmine based on how Polymer wrote tests with Mocha for their components.I am able to run those tests successfully if I run them individually.

By taking a look at Polymer's core tests ,what I understand is that there is a custom test runner that uses mocha-htmltest.js to launch each of the polymer element tests(each an html in itself) in an iframe and then destroy it for every test.The results to display are passed to the main window for every test. In this approach,each polymer element test html running within an iframe imports all the libraries needed(jasmine,platform,polymer).

Isn't this a costly approach to re-construct iframes importing all libraries for each element's test? Is there any alternate ways for running multiple polymer element tests?

I could not find alternative approaches without one test polluting the other.(Faced issues like being able to listen to polymer-ready only for the first element test)

Can anyone share some thoughts on how you managed to run multiple polymer elements' tests with karma as the test runner?

Thanks, vj.

Answer 1

We chose the iframe approach because we wanted to write tests in plain HTML without resorting to javascript innerHTML tricks, and we use karma to test in all of our supported browsers. iframes gives us both of our requirements, at the expense of taking a while to run.

I must note that we typically test a number of related things in iframes because the cost is so high. In that sense we use them at somewhere between a "suite" and a "test" in mocha's terminology.

Perhaps at some point in the future, a lighter layer can be made (ES6/7 Realms + ShadowDOM?) that gives us a clean context for our test runs, but the speed hit is not especially heinous to us for now.