Provide guidance that any variable with a reference to a DOM element should be nulled

[notmessenger]

KNOWN
@sophypal has discovered that references to DOM elements in acceptance tests that are not assigned null in an afterEach() do not allow garbage collection to be performed and drastically increase the memory footprint of the test suite.

UNKOWN

• If there are other variables in acceptance tests that cause the same issues (other than what is already identified in Provide guidance that the variable the acceptance application is set on in tests should be nulled out #26), or only if it's only DOM ones
• If this applies to component integration tests as well (meaning is there a time where such assignment is occurring, not that the memory management should be handled any differently).

[sglanzer-deprecated]

I would love love love to have a generic testing solution to look for proper destruction of objects

[sophypal]

If there are other variables in acceptance tests that cause the same issues (other than what is already identified in #26), or only if it's only DOM ones

Any references held will not be reclaimed but usually not an issue to worry about generally in our tests. DOM nodes specifically need to be addressed because a single detached node will keep the DOM tree alive in memory. To that end, I wouldn't say it increases the memory footprint drastically. Ultimately it will depend on the number of left over references but it would be a good idea to maintain the practice of always unsetting it (when dealing with DOM references).

If this applies to component integration tests as well (meaning is there a time where such assignment is occurring, not that the memory management should be handled any differently).

This would apply to all tests (acceptance/integration/unit). Yes, you can actually render in unit test.

[sophypal]

So references we should be looking out for that really leaks are Ember objects that hold a reference to the container. ember-test-helpers does a good job of cleaning out test contexts which holds references to the container and registry but we also need to null references to the application instance in Acceptance tests.