Min cancel delay >= 0

tests/test_tractor.py

@@ -401,13 +401,13 @@ def test_a_quadruple_example(time_quad_ex):
 
 @pytest.mark.parametrize(
     'cancel_delay',
-    list(map(lambda i: i/10, range(3, 10)))
+    list(map(lambda i: i/10, range(2, 8)))
 )
 def test_not_fast_enough_quad(arb_addr, time_quad_ex, cancel_delay):
     """Verify we can cancel midway through the quad example and all actors
     cancel gracefully.
     """
     results, diff = time_quad_ex
-    delay = diff - cancel_delay
+    delay = max(diff - cancel_delay, 0)
     results = tractor.run(cancel_after, delay, arbiter_addr=arb_addr)
     assert results is None