add tests

Author: NorthIsUp

src/aiolimiter/leakybucket.py

@@ -133,7 +133,7 @@ def estimated_wait_time(self, amount: float = 1) -> float:
         :param amount: How much capacity you need to be available.
         """
         self._leak()
-        return (amount - self._level) / self._rate_per_sec
+        return abs(amount - self._level) / self._rate_per_sec
 
     async def acquire(self, amount: float = 1) -> None:
         """Acquire capacity in the limiter.

tests/test_aiolimiter.py

@@ -134,10 +134,16 @@ async def test_acquire_wait_time():
         pending = await wait_for_n_done([task], 0)
         assert pending
 
+        assert limiter.has_capacity()
+        assert limiter.estimated_wait_time() == 0
+
         mocked_time.current_time = 1
         pending = await wait_for_n_done([task], 1)
         assert not pending
 
+        assert not limiter.has_capacity()
+        assert limiter.estimated_wait_time() == 2
+
 
 async def test_decreasing_acquire():
     limiter = AsyncLimiter(3, 3)