1 files changed, 40 insertions, 0 deletions
diff --git a/venv/lib/python3.9/site-packages/trio/tests/test_scheduler_determinism.py b/venv/lib/python3.9/site-packages/trio/tests/test_scheduler_determinism.py
new file mode 100644
index 00000000..e2d3167e
--- /dev/null
+++ b/venv/lib/python3.9/site-packages/trio/tests/test_scheduler_determinism.py
@@ -0,0 +1,40 @@
+import trio
+
+
+async def scheduler_trace():
+    """Returns a scheduler-dependent value we can use to check determinism."""
+    trace = []
+
+    async def tracer(name):
+        for i in range(50):
+            trace.append((name, i))
+            await trio.sleep(0)
+
+    async with trio.open_nursery() as nursery:
+        for i in range(5):
+            nursery.start_soon(tracer, i)
+
+    return tuple(trace)
+
+
+def test_the_trio_scheduler_is_not_deterministic():
+    # At least, not yet.  See https://github.com/python-trio/trio/issues/32
+    traces = []
+    for _ in range(10):
+        traces.append(trio.run(scheduler_trace))
+    assert len(set(traces)) == len(traces)
+
+
+def test_the_trio_scheduler_is_deterministic_if_seeded(monkeypatch):
+    monkeypatch.setattr(trio._core._run, "_ALLOW_DETERMINISTIC_SCHEDULING", True)
+    traces = []
+    for _ in range(10):
+        state = trio._core._run._r.getstate()
+        try:
+            trio._core._run._r.seed(0)
+            traces.append(trio.run(scheduler_trace))
+        finally:
+            trio._core._run._r.setstate(state)
+
+    assert len(traces) == 10
+    assert len(set(traces)) == 1