Right now there only a single test to ensure `priority` works correctly in `scheduler`: https://github.com/python/cpython/blob/fea7290a0ecee09bbce571d4d10f5881b7ea3485/Lib/test/test_sched.py#L90-L97

It looks like it is not enough. Why?

```
for priority in [1, 2, 3, 4, 5]:
  z = scheduler.enterabs(0.01, priority, fun, (priority,))
scheduler.run()
self.assertEqual(l, [1, 2, 3, 4, 5])
```

This test does not actually test different priorities. It only tests that a direct one works correctly. But, this might be a pure coincidence that numbers match. They are spawned in this particular order.

What if there are equal numbers? Like `[1, 2, 1]`

I propose adding more examples to this test. PR is on its way.