Better A4A/FIE testing, add FIE services regression test

[dreamofabear]

• Refactor amp4test.js to be configurable. Eg. it can now test amp4email spec, A4A FIE with arbitrary content, etc.
• Add BrowserController.waitForElementReady() to wait for custom elements to finish initializing (layout) before taking action.
• Add regression test for FIE services refactor in Refactor EmbeddableService #19771.

---

You can now pass spec: 'amp'|'amp4ads'|'amp4email' to describes.integration and it will generate a correctly formatted AMP document according to the chosen spec.

Test an A4A/FIE with arbitrary markup

const myAdSrc = addParamsToUrl('/amp4test/compose-doc', {
  body: ...,
  extensions: ...,
  spec: 'amp4ads',
});

describes.integration('My A4A test', {
  body: `
    <amp-ad width=300 height=400
        id="i-amphtml-demo-id" type="fake" 
        src="${myAdSrc}">
    </amp-ad>`,
  }, env => {
  ...
});

Test an AMP4EMAIL doc

describes.integration('My AMP4EMAIL test', {
  body: ...,
  spec: 'amp4email',
  }, env => {
  ...
});

[dreamofabear]

/to @lannka

Still need to fix a few integration test failures likely due to amp4test.js changes.

[dreamofabear]

I think the problem right now is that test code doesn't wait for extensions to "be ready". E.g. a "click" event can happen before amp-analytics has a chance to setup the "click" trigger.

[lannka]

I think the problem right now is that test code doesn't wait for extensions to "be ready". E.g. a "click" event can happen before amp-analytics has a chance to setup the "click" trigger.

Did your waitForReady function help?

I like your refactoring, good work!

[dreamofabear]

Yup, that was the idea. Thanks!