Allow async exec test to reject

[hzoo]

Ref #4576 (comment) and commited in 5ea57d5

In an exec test, you can now return a promise. We use mochajs.org for tests and returning a promise will cause it to asynchronously call done.

babel/packages/babel-plugin-transform-async-generator-functions/test/fixtures/for-await/async-generator-exec/exec.js

Lines 22 to 25 in 5ea57d5

	return forEach(genAnswers(), function(val) { output += val.value })
	.then(function () {
	assert.equal(output, 42);
	});

return forEach(genAnswers(), function(val) { output += val.value })
.then(function () {
  assert.equal(output, 42);
});

You need to add to options.json (to fix parser error)

{
  "parserOpts": {
      "allowReturnOutsideFunction": true
   }
}

The suggestion is to allow a rejection instead of just .then

[oleksandr-kuzmenko]

@hzoo hi, this issue is already possible to close)

[hzoo]

When did someone add it? I definetely don't remember adding it. There's no test with a return a().catch()

[oleksandr-kuzmenko]

@hzoo I can add this test