The following works in 0.18.2:

test(t => {
	t.notThrows(new Promise(resolve => {
		setTimeout(() => {
			t.pass();
			resolve();
		}, 100);
	}));
});

On master, it fails with:

Assertion passed, but test has already ended

We should wait until all pending assertions have resolved before declaring a test "finished" and throwing when new assertions show up.

Adding a call to t.plan() causes it to behave oddly going all the way back (we even added a test solidifying this odd behavior in #360):

test(t => {
   t.notThrows(new Promise(resolve => {
       t.plan(2);
       setTimeout(() => {
         t.pass();
         resolve();
       }, 100);
   }));
});

The above fails with:

Planned for 2 assertions, but got 1.

Similar results for as far back as I tested.

I think we should allow for added assertions, as long as we still have pending assertions. When t.plan is used, I don't think we should check for too few assertions until we've drained all pending assertions.