add a simple test to run

tests/test_run.py

@@ -0,0 +1,37 @@
+import asyncio
+from unittest.mock import ANY
+
+import pytest
+
+import qasync
+
+
+@pytest.fixture
+def get_event_loop_coro():
+    async def coro(expected_debug):
+        event_loop = asyncio.get_event_loop()
+        assert type(event_loop) is qasync.QEventLoop
+        assert event_loop.get_debug() == expected_debug
+        await asyncio.sleep(0)
+
+    return coro
+
+
+def test_qasync_run_restores_loop(get_event_loop_coro):
+    asyncio.set_event_loop(None)
+    qasync.run(get_event_loop_coro(ANY))
+
+    with pytest.raises(RuntimeError):
+        _ = asyncio.get_event_loop()
+
+
+def test_qasync_run_restores_policy(get_event_loop_coro):
+    old_policy = asyncio.get_event_loop_policy()
+    qasync.run(get_event_loop_coro(ANY))
+    new_policy = asyncio.get_event_loop_policy()
+    assert type(old_policy) is type(new_policy)
+
+
+def test_qasync_run_with_debug_args(get_event_loop_coro):
+    qasync.run(get_event_loop_coro(True), debug=True)
+    qasync.run(get_event_loop_coro(False), debug=False)