diff --git a/docs/source/conf.py b/docs/source/conf.py
index 7a71ac8..ff74f8b 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -45,6 +45,7 @@
     ("py:obj", "bytes-like"),
 ]
 
+
 # XX hack the RTD theme until
 #   https://github.com/rtfd/sphinx_rtd_theme/pull/382
 # is shipped (should be in the release after 0.2.4)
diff --git a/pytest_trio/_tests/test_async_fixture.py b/pytest_trio/_tests/test_async_fixture.py
index 88c4aa9..3703f73 100644
--- a/pytest_trio/_tests/test_async_fixture.py
+++ b/pytest_trio/_tests/test_async_fixture.py
@@ -2,7 +2,6 @@
 
 
 def test_single_async_fixture(testdir):
-
     testdir.makepyfile(
         """
         import pytest
@@ -25,7 +24,6 @@ async def test_simple(fix1):
 
 
 def test_async_fixture_recomputed_for_each_test(testdir):
-
     testdir.makepyfile(
         """
         import pytest
@@ -56,7 +54,6 @@ async def test_second(fix1):
 
 
 def test_nested_async_fixture(testdir):
-
     testdir.makepyfile(
         """
         import pytest
@@ -89,7 +86,6 @@ async def test_both(fix1, fix2):
 
 
 def test_async_within_sync_fixture(testdir):
-
     testdir.makepyfile(
         """
         import pytest
@@ -122,7 +118,6 @@ async def test_simple(sync_fix):
 # async fixture...
 @pytest.mark.xfail(reason="Not implemented yet")
 def test_raise_in_async_fixture_cause_pytest_error(testdir):
-
     testdir.makepyfile(
         """
         import pytest
diff --git a/pytest_trio/_tests/test_async_yield_fixture.py b/pytest_trio/_tests/test_async_yield_fixture.py
index ca99159..9505eb2 100644
--- a/pytest_trio/_tests/test_async_yield_fixture.py
+++ b/pytest_trio/_tests/test_async_yield_fixture.py
@@ -38,7 +38,6 @@ def test_after():
 
 
 def test_nested_async_yield_fixture(testdir):
-
     testdir.makepyfile(
         """
         import pytest
@@ -93,7 +92,6 @@ def test_after():
 
 
 def test_async_yield_fixture_within_sync_fixture(testdir):
-
     testdir.makepyfile(
         """
         import pytest
@@ -139,7 +137,6 @@ def test_after():
 
 
 def test_async_yield_fixture_within_sync_yield_fixture(testdir):
-
     testdir.makepyfile(
         """
         import pytest
@@ -190,7 +187,6 @@ def test_after():
 
 
 def test_async_yield_fixture_with_multiple_yields(testdir):
-
     testdir.makepyfile(
         """
         import pytest
@@ -217,7 +213,6 @@ async def test_actual_test(fix1):
 
 
 def test_async_yield_fixture_with_nursery(testdir):
-
     testdir.makepyfile(
         """
         import pytest
@@ -253,7 +248,6 @@ async def test_actual_test(server):
 
 
 def test_async_yield_fixture_crashed_teardown_allow_other_teardowns(testdir):
-
     testdir.makepyfile(
         """
         import pytest
diff --git a/pytest_trio/_tests/test_basic.py b/pytest_trio/_tests/test_basic.py
index 9702498..f95538f 100644
--- a/pytest_trio/_tests/test_basic.py
+++ b/pytest_trio/_tests/test_basic.py
@@ -2,7 +2,6 @@
 
 
 def test_async_test_is_executed(testdir):
-
     testdir.makepyfile(
         """
         import pytest
@@ -27,7 +26,6 @@ def test_check_async_test_called():
 
 
 def test_async_test_as_class_method(testdir):
-
     testdir.makepyfile(
         """
         import pytest
@@ -60,7 +58,6 @@ def test_check_async_test_called():
 
 @pytest.mark.xfail(reason="Raises pytest internal error so far...")
 def test_sync_function_with_trio_mark(testdir):
-
     testdir.makepyfile(
         """
         import pytest
@@ -77,7 +74,6 @@ def test_invalid():
 
 
 def test_skip_and_xfail(testdir):
-
     testdir.makepyfile(
         """
         import functools
diff --git a/pytest_trio/_tests/test_hypothesis_interaction.py b/pytest_trio/_tests/test_hypothesis_interaction.py
index 75aa9f7..cb95a96 100644
--- a/pytest_trio/_tests/test_hypothesis_interaction.py
+++ b/pytest_trio/_tests/test_hypothesis_interaction.py
@@ -1,10 +1,5 @@
 import pytest
 import trio
-from trio.tests.test_scheduler_determinism import (
-    scheduler_trace,
-    test_the_trio_scheduler_is_not_deterministic,
-    test_the_trio_scheduler_is_deterministic_if_seeded,
-)
 from hypothesis import given, settings, strategies as st
 
 from pytest_trio.plugin import _trio_test_runner_factory
@@ -38,6 +33,22 @@ async def test_mark_and_parametrize(x, y):
     assert y in (1, 2)
 
 
+async def scheduler_trace():
+    """Returns a scheduler-dependent value we can use to check determinism."""
+    trace = []
+
+    async def tracer(name):
+        for i in range(10):
+            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_deterministic_under_hypothesis():
     traces = []
 
diff --git a/pytest_trio/_tests/test_sync_fixture.py b/pytest_trio/_tests/test_sync_fixture.py
index 738ffbc..c6060a4 100644
--- a/pytest_trio/_tests/test_sync_fixture.py
+++ b/pytest_trio/_tests/test_sync_fixture.py
@@ -12,7 +12,6 @@ async def test_single_sync_fixture(sync_fix):
 
 
 def test_single_yield_fixture(testdir):
-
     testdir.makepyfile(
         """
         import pytest
@@ -47,7 +46,6 @@ def test_after():
 
 
 def test_single_yield_fixture_with_async_deps(testdir):
-
     testdir.makepyfile(
         """
         import pytest
@@ -90,7 +88,6 @@ def test_after():
 
 
 def test_sync_yield_fixture_crashed_teardown_allow_other_teardowns(testdir):
-
     testdir.makepyfile(
         """
         import pytest