test(upgrade): properly clean up after tests to avoid errors in unrelated tests (#28013)
Many `ngUpgrade` tests need to manually [bootstrap modules][1] (instead
of using `TestBed` which automatically cleans up) and thus need to also
manually clean up afterwards (e.g. by calling [destroyPlatform()][2]
after each test).
Failing to destroy the platform is usually not a problem, unless the
next test tries to manually destroy it (as a precaution), as happens
[here][3] (among other places).
More specifically, the problem happens, because (as part of the clean-up
happening on platform destruction) upgraded components will try to
[call a method][4] on `angular.element` after `angular` has been
[set to `undefined`][5] (assuming the last test was using the
[withEachNg1Version()][6] helper).
Because the test order is pseudo-random and thus different on each run,
these errors did not always come up and - when they did- they would go
away after a couple of reruns, making them appear as flakes on CI.
(For reference, the issue was introduced in 43c33d566.)
This commit eliminates the issue by always destroying the platform after
each `ngUpgrade` test.
Jira issue: FW-924
[1]: c3aa24c3f9/packages/upgrade/test/static/test_helpers.ts (L21)
[2]: c3aa24c3f9/packages/upgrade/test/static/integration/upgrade_component_spec.ts (L24)
[3]: c3aa24c3f9/packages/elements/test/create-custom-element_spec.ts (L31)
[4]: c3aa24c3f9/packages/upgrade/src/common/upgrade_helper.ts (L134-L135)
[5]: c3aa24c3f9/packages/upgrade/test/common/test_helpers.ts (L115)
[6]: c3aa24c3f9/packages/upgrade/test/common/test_helpers.ts (L31)
PR Close #28013
4e17212d44