DOM: add tests for AbortSignal.reason

[nidhijaju]

Add tests for AbortSignal's new abort reason property.

See whatwg/dom#1027 for accompanying spec change.

[yutakahirano]

Can you add descriptions to assertions? Descriptions don't have to be long (I feel "signal reason should be set when controller is aborted" is a bit too long). Assertion description is useful to find the failed assertion in a test, so it can be anything as long as it is unique in the test.

So the first test case can be:

  ...
  assert_true(signal.aborted, "signal.abort");
  assert_equals(signal.reason, reason, "signal.reason");

[nidhijaju]

Makes sense! I've added assertion descriptions to my tests based on your suggestion.

[nidhijaju]

@annevk Is it okay if you also take a look to see if the tests in this PR look okay to you?

[annevk]

I recommend running the tests even if they will fail to spot syntax errors and such.

[annevk]

For the new tests it seems good to assert some fields before calling abort() as well. At least once. E.g., assert_true("reason" in signal) and assert_equals(signal.reason, undefined).

[yutakahirano]

LGTM.