Test support for waiting on property or attribute changes

[nwhittaker]

When programmatically changing a Stencil element's properties or attributes, the change is propagated asynchronously. In a test environment, it's typical to set a property or attribute on an element and then verify some change occurred. However, with a stencil component, it's difficult to reliably determine when it's safe to inspect the element for the changed behavior.

Stencil's own testing tools provide ways to wait for property/attribute changes to take effect:

• Unit tests: newSpecPage().waitForChanges()
• E2E tests: E2EPage.waitForChanges()

I tried awaiting on nextRAF(), but that didn't seem to guarantee anything about the state of the stencil element and still lead to random failures.

This latency has been a significant point of pain for writing tests. Is it possible to get a test helper, or something, that provides a way to wait for property and attribute changes to take effect?