diff --git a/check/pytest b/check/pytest
index 24f792899cf..e63bf6c07cf 100755
--- a/check/pytest
+++ b/check/pytest
@@ -33,6 +33,9 @@ if [ "$PYTHON_VERSION" -lt "37" ]; then
   PYTEST_ARGS+=("--ignore=cirq-rigetti")
 fi
 
+: ${CIRQ_TESTING_RANDOM_SEED=$(git log -1 --pretty="%ct")}
+export CIRQ_TESTING_RANDOM_SEED
+
 if [ -z "${ACTUALLY_QUIET}" ]; then
     pytest "${PYTEST_ARGS[@]}"
     RESULT=$?
diff --git a/check/pytest-changed-files b/check/pytest-changed-files
index fd623377b18..9b57b1bf7bd 100755
--- a/check/pytest-changed-files
+++ b/check/pytest-changed-files
@@ -77,4 +77,7 @@ fi
 
 source dev_tools/pypath
 
+: ${CIRQ_TESTING_RANDOM_SEED=$(git log -1 --pretty="%ct")}
+export CIRQ_TESTING_RANDOM_SEED
+
 pytest ${rest} "${changed[@]}"
diff --git a/cirq-core/cirq/contrib/acquaintance/gates_test.py b/cirq-core/cirq/contrib/acquaintance/gates_test.py
index 099aa4721db..cff4f361360 100644
--- a/cirq-core/cirq/contrib/acquaintance/gates_test.py
+++ b/cirq-core/cirq/contrib/acquaintance/gates_test.py
@@ -17,7 +17,7 @@
 from string import ascii_lowercase as alphabet
 from typing import Optional, Sequence, Tuple
 
-import numpy as np
+import numpy
 import pytest
 
 import cirq
@@ -232,9 +232,8 @@ def test_swap_network_init_error():
         cca.SwapNetworkGate((3,))
 
 
-rng = np.random.default_rng()
 part_lens_and_acquaintance_sizes = [
-    [[l + 1 for l in rng.poisson(size=n_parts, lam=lam)], rng.poisson(4)]
+    [[l + 1 for l in numpy.random.poisson(size=n_parts, lam=lam)], numpy.random.poisson(4)]
     for n_parts, lam in product(range(2, 20, 3), range(1, 4))
 ]
 
diff --git a/cirq-core/cirq/ops/common_gates_test.py b/cirq-core/cirq/ops/common_gates_test.py
index 2e64e0d2940..d593be664f0 100644
--- a/cirq-core/cirq/ops/common_gates_test.py
+++ b/cirq-core/cirq/ops/common_gates_test.py
@@ -1042,10 +1042,10 @@ def test_ixyz_circuit_diagram():
 @pytest.mark.parametrize(
     'theta,exp',
     [
-        {sympy.Symbol("theta"), 1 / 2},
-        {np.pi / 2, 1 / 2},
-        {np.pi / 2, sympy.Symbol("exp")},
-        {sympy.Symbol("theta"), sympy.Symbol("exp")},
+        (sympy.Symbol("theta"), 1 / 2),
+        (np.pi / 2, 1 / 2),
+        (np.pi / 2, sympy.Symbol("exp")),
+        (sympy.Symbol("theta"), sympy.Symbol("exp")),
     ],
 )
 def test_rxyz_exponent(theta, exp):
diff --git a/cirq-core/cirq/protocols/json_serialization_test.py b/cirq-core/cirq/protocols/json_serialization_test.py
index e102cebfdda..51244fd22c1 100644
--- a/cirq-core/cirq/protocols/json_serialization_test.py
+++ b/cirq-core/cirq/protocols/json_serialization_test.py
@@ -537,11 +537,14 @@ def _list_public_classes_for_tested_modules():
     # to remove DeprecationWarning noise during test collection
     with warnings.catch_warnings():
         warnings.simplefilter("ignore")
-        return [
-            (mod_spec, o, n)
-            for mod_spec in MODULE_TEST_SPECS
-            for (o, n) in mod_spec.find_classes_that_should_serialize()
-        ]
+        return sorted(
+            (
+                (mod_spec, n, o)
+                for mod_spec in MODULE_TEST_SPECS
+                for (n, o) in mod_spec.find_classes_that_should_serialize()
+            ),
+            key=lambda mno: (str(mno[0]), mno[1]),
+        )
 
 
 @pytest.mark.parametrize(
diff --git a/conftest.py b/conftest.py
index e74e741ee54..099d4971cd1 100644
--- a/conftest.py
+++ b/conftest.py
@@ -12,6 +12,16 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import os
+import random
+
+# allow CI execution of isolated_packages_test.py without numpy
+try:
+    import numpy
+except ImportError:
+    # coverage: ignore
+    numpy = None
+
 
 def pytest_configure(config):
     # Ignore deprecation warnings in python code generated from our protobuf definitions.
@@ -35,3 +45,10 @@ def pytest_addoption(parser):
         default=False,
         help="run Rigetti integration tests",
     )
+
+
+# skip seeding for unset or empty CIRQ_TESTING_RANDOM_SEED
+if numpy is not None and os.environ.get('CIRQ_TESTING_RANDOM_SEED'):
+    rngseed = int(os.environ['CIRQ_TESTING_RANDOM_SEED'])
+    random.seed(rngseed)
+    numpy.random.seed(rngseed)