tests/extmod: Add test for uasyncio.sleep of a negative time.

It should take 0 time to await on a negative sleep.

Signed-off-by: Damien George <damien@micropython.org>

tests/extmod/uasyncio_basic.py

@@ -36,8 +36,16 @@ async def main():
     t1 = ticks()
     await delay_print(0.04, "long")
     t2 = ticks()
+    await delay_print(-1, "negative")
+    t3 = ticks()
 
-    print("took {} {}".format(round(ticks_diff(t1, t0), -1), round(ticks_diff(t2, t1), -1)))
+    print(
+        "took {} {} {}".format(
+            round(ticks_diff(t1, t0), -1),
+            round(ticks_diff(t2, t1), -1),
+            round(ticks_diff(t3, t2), -1),
+        )
+    )
 
 
 asyncio.run(main())

tests/extmod/uasyncio_basic.py.exp

@@ -2,4 +2,5 @@ start
 after sleep
 short
 long
-took 20 40
+negative
+took 20 40 0