local salt marker

tests/conftest.py

@@ -43,12 +43,6 @@ class DummyDevice(DefaultGaussian):
     _operation_map["Kerr"] = lambda *x, **y: np.identity(2)
 
 
-@pytest.fixture(autouse=True)
-def set_numpy_seed():
-    np.random.seed(9872653)
-    yield
-
-
 @pytest.fixture(scope="session")
 def tol():
     """Numerical tolerance for equality tests."""
@@ -184,6 +178,37 @@ def legacy_opmath_only():
         pytest.skip("This test exclusively tests legacy opmath")
 
 
+#######################################################################
+
+
+@pytest.fixture
+def seed(request):
+    """An integer random number generator seed
+
+    This fixture overrides the ``seed`` fixture provided by pytest-rng, adding the flexibility
+    of locally getting a new seed for a test case by applying the ``local_salt`` marker. This is
+    useful when the seed from pytest-rng happens to be a bad seed that causes your test to fail.
+
+    .. code_block:: python
+
+        @pytest.mark.local_salt(42)
+        def test_something(seed):
+            ...
+
+    The value passed to ``local_salt`` needs to be an integer.
+
+    """
+
+    fixture_manager = request._fixturemanager  # pylint:disable=protected-access
+    fixture_defs = fixture_manager.getfixturedefs("seed", request.node)
+    original_fixture_def = fixture_defs[0]  # the original seed fixture provided by pytest-rng
+    original_seed = original_fixture_def.func(request)
+    marker = request.node.get_closest_marker("local_salt")
+    if marker and marker.args:
+        return original_seed + marker.args[0]
+    return original_seed
+
+
 #######################################################################
 
 try:

tests/devices/qubit/test_simulate.py

@@ -1559,14 +1559,14 @@ def test_tree_traversal_combine_measurements(self, measurements, expected):
         else:
             assert qml.math.allclose(combined_measurement, expected)
 
+    @pytest.mark.local_salt(2)
     @pytest.mark.parametrize("ml_framework", ml_frameworks_list)
     @pytest.mark.parametrize(
         "postselect_mode", [None, "hw-like", "pad-invalid-samples", "fill-shots"]
     )
     def test_simulate_one_shot_native_mcm(self, ml_framework, postselect_mode, seed):
         """Unit tests for simulate_one_shot_native_mcm"""
 
-        seed = seed + 2
         with qml.queuing.AnnotatedQueue() as q:
             qml.RX(np.pi / 4, wires=0)
             m = qml.measure(wires=0, postselect=0)

tests/pytest.ini

@@ -19,6 +19,7 @@ markers =
     logging: marks tests for pennylane logging
     external: marks tests that require external packages such as matplotlib and PyZX
     catalyst: marks tests for catalyst testing (select with '-m "catalyst"')
+    local_salt(salt): adds a salt to the seed provided by the pytest-rng fixture
 filterwarnings =
     ignore::DeprecationWarning:autograd.numpy.numpy_wrapper
     ignore:Casting complex values to real::autograd.numpy.numpy_wrapper