diff --git a/tests/test_core/test_decorator_calls.py b/tests/test_core/test_decorator_calls.py
index a329f8bcd..05c23f1cb 100644
--- a/tests/test_core/test_decorator_calls.py
+++ b/tests/test_core/test_decorator_calls.py
@@ -1,5 +1,4 @@
 import boto3
-import os
 import pytest
 import sure  # noqa # pylint: disable=unused-import
 import unittest
@@ -20,12 +19,12 @@ def test_basic_decorator():
 
 
 @pytest.fixture
-def aws_credentials():
+def aws_credentials(monkeypatch):
     """Mocked AWS Credentials for moto."""
-    os.environ["AWS_ACCESS_KEY_ID"] = "testing"
-    os.environ["AWS_SECRET_ACCESS_KEY"] = "testing"
-    os.environ["AWS_SECURITY_TOKEN"] = "testing"
-    os.environ["AWS_SESSION_TOKEN"] = "testing"
+    monkeypatch.setenv("AWS_ACCESS_KEY_ID", "testing")
+    monkeypatch.setenv("AWS_SECRET_ACCESS_KEY", "testing")
+    monkeypatch.setenv("AWS_SECURITY_TOKEN", "testing")
+    monkeypatch.setenv("AWS_SESSION_TOKEN", "testing")
 
 
 @pytest.mark.network
diff --git a/tests/test_core/test_importorder.py b/tests/test_core/test_importorder.py
index 9a00507d4..d4f3a3457 100644
--- a/tests/test_core/test_importorder.py
+++ b/tests/test_core/test_importorder.py
@@ -3,19 +3,18 @@ import pytest
 import sure  # noqa # pylint: disable=unused-import
 from moto import mock_s3
 from moto import settings
-from os import environ
 from unittest import SkipTest
 
 
 @pytest.fixture(scope="function")
-def aws_credentials():
+def aws_credentials(monkeypatch):
     if settings.TEST_SERVER_MODE:
         raise SkipTest("No point in testing this in ServerMode.")
     """Mocked AWS Credentials for moto."""
-    environ["AWS_ACCESS_KEY_ID"] = "testing"
-    environ["AWS_SECRET_ACCESS_KEY"] = "testing"
-    environ["AWS_SECURITY_TOKEN"] = "testing"
-    environ["AWS_SESSION_TOKEN"] = "testing"
+    monkeypatch.setenv("AWS_ACCESS_KEY_ID", "testing")
+    monkeypatch.setenv("AWS_SECRET_ACCESS_KEY", "testing")
+    monkeypatch.setenv("AWS_SECURITY_TOKEN", "testing")
+    monkeypatch.setenv("AWS_SESSION_TOKEN", "testing")
 
 
 def test_mock_works_with_client_created_inside(
diff --git a/tests/test_efs/test_access_point_tagging.py b/tests/test_efs/test_access_point_tagging.py
index ab70296e9..4bc06d37c 100644
--- a/tests/test_efs/test_access_point_tagging.py
+++ b/tests/test_efs/test_access_point_tagging.py
@@ -1,5 +1,3 @@
-from os import environ
-
 import boto3
 import pytest
 
@@ -7,12 +5,12 @@ from moto import mock_efs
 
 
 @pytest.fixture(scope="function")
-def aws_credentials():
+def aws_credentials(monkeypatch):
     """Mocked AWS Credentials for moto."""
-    environ["AWS_ACCESS_KEY_ID"] = "testing"
-    environ["AWS_SECRET_ACCESS_KEY"] = "testing"
-    environ["AWS_SECURITY_TOKEN"] = "testing"
-    environ["AWS_SESSION_TOKEN"] = "testing"
+    monkeypatch.setenv("AWS_ACCESS_KEY_ID", "testing")
+    monkeypatch.setenv("AWS_SECRET_ACCESS_KEY", "testing")
+    monkeypatch.setenv("AWS_SECURITY_TOKEN", "testing")
+    monkeypatch.setenv("AWS_SESSION_TOKEN", "testing")
 
 
 @pytest.fixture(scope="function")
diff --git a/tests/test_efs/test_access_points.py b/tests/test_efs/test_access_points.py
index 2523eff68..b3e45fc33 100644
--- a/tests/test_efs/test_access_points.py
+++ b/tests/test_efs/test_access_points.py
@@ -1,5 +1,3 @@
-from os import environ
-
 import boto3
 import pytest
 from botocore.exceptions import ClientError
@@ -9,12 +7,12 @@ from moto.core import ACCOUNT_ID
 
 
 @pytest.fixture(scope="function")
-def aws_credentials():
+def aws_credentials(monkeypatch):
     """Mocked AWS Credentials for moto."""
-    environ["AWS_ACCESS_KEY_ID"] = "testing"
-    environ["AWS_SECRET_ACCESS_KEY"] = "testing"
-    environ["AWS_SECURITY_TOKEN"] = "testing"
-    environ["AWS_SESSION_TOKEN"] = "testing"
+    monkeypatch.setenv("AWS_ACCESS_KEY_ID", "testing")
+    monkeypatch.setenv("AWS_SECRET_ACCESS_KEY", "testing")
+    monkeypatch.setenv("AWS_SECURITY_TOKEN", "testing")
+    monkeypatch.setenv("AWS_SESSION_TOKEN", "testing")
 
 
 @pytest.fixture(scope="function")
diff --git a/tests/test_efs/test_file_system.py b/tests/test_efs/test_file_system.py
index d6f04cb2f..25caeb03e 100644
--- a/tests/test_efs/test_file_system.py
+++ b/tests/test_efs/test_file_system.py
@@ -1,5 +1,4 @@
 import re
-from os import environ
 
 import boto3
 import pytest
@@ -32,12 +31,12 @@ SAMPLE_2_PARAMS = {
 
 
 @pytest.fixture(scope="function")
-def aws_credentials():
+def aws_credentials(monkeypatch):
     """Mocked AWS Credentials for moto."""
-    environ["AWS_ACCESS_KEY_ID"] = "testing"
-    environ["AWS_SECRET_ACCESS_KEY"] = "testing"
-    environ["AWS_SECURITY_TOKEN"] = "testing"
-    environ["AWS_SESSION_TOKEN"] = "testing"
+    monkeypatch.setenv("AWS_ACCESS_KEY_ID", "testing")
+    monkeypatch.setenv("AWS_SECRET_ACCESS_KEY", "testing")
+    monkeypatch.setenv("AWS_SECURITY_TOKEN", "testing")
+    monkeypatch.setenv("AWS_SESSION_TOKEN", "testing")
 
 
 @pytest.fixture(scope="function")
diff --git a/tests/test_efs/test_filesystem_tagging.py b/tests/test_efs/test_filesystem_tagging.py
index a0d7dae9b..a01135346 100644
--- a/tests/test_efs/test_filesystem_tagging.py
+++ b/tests/test_efs/test_filesystem_tagging.py
@@ -1,5 +1,3 @@
-from os import environ
-
 import boto3
 import pytest
 
@@ -7,12 +5,12 @@ from moto import mock_efs
 
 
 @pytest.fixture(scope="function")
-def aws_credentials():
+def aws_credentials(monkeypatch):
     """Mocked AWS Credentials for moto."""
-    environ["AWS_ACCESS_KEY_ID"] = "testing"
-    environ["AWS_SECRET_ACCESS_KEY"] = "testing"
-    environ["AWS_SECURITY_TOKEN"] = "testing"
-    environ["AWS_SESSION_TOKEN"] = "testing"
+    monkeypatch.setenv("AWS_ACCESS_KEY_ID", "testing")
+    monkeypatch.setenv("AWS_SECRET_ACCESS_KEY", "testing")
+    monkeypatch.setenv("AWS_SECURITY_TOKEN", "testing")
+    monkeypatch.setenv("AWS_SESSION_TOKEN", "testing")
 
 
 @pytest.fixture(scope="function")
diff --git a/tests/test_efs/test_lifecycle_config.py b/tests/test_efs/test_lifecycle_config.py
index fbabe2162..c03c91534 100644
--- a/tests/test_efs/test_lifecycle_config.py
+++ b/tests/test_efs/test_lifecycle_config.py
@@ -1,5 +1,3 @@
-from os import environ
-
 import boto3
 import pytest
 from botocore.exceptions import ClientError
@@ -8,12 +6,12 @@ from moto import mock_efs
 
 
 @pytest.fixture(scope="function")
-def aws_credentials():
+def aws_credentials(monkeypatch):
     """Mocked AWS Credentials for moto."""
-    environ["AWS_ACCESS_KEY_ID"] = "testing"
-    environ["AWS_SECRET_ACCESS_KEY"] = "testing"
-    environ["AWS_SECURITY_TOKEN"] = "testing"
-    environ["AWS_SESSION_TOKEN"] = "testing"
+    monkeypatch.setenv("AWS_ACCESS_KEY_ID", "testing")
+    monkeypatch.setenv("AWS_SECRET_ACCESS_KEY", "testing")
+    monkeypatch.setenv("AWS_SECURITY_TOKEN", "testing")
+    monkeypatch.setenv("AWS_SESSION_TOKEN", "testing")
 
 
 @pytest.fixture(scope="function")
diff --git a/tests/test_efs/test_mount_target.py b/tests/test_efs/test_mount_target.py
index 6e2e31632..7b4a1d2e5 100644
--- a/tests/test_efs/test_mount_target.py
+++ b/tests/test_efs/test_mount_target.py
@@ -1,6 +1,5 @@
 import re
 import sys
-from os import environ
 from ipaddress import IPv4Network
 
 import boto3
@@ -38,12 +37,12 @@ else:
 
 
 @pytest.fixture(scope="function")
-def aws_credentials():
+def aws_credentials(monkeypatch):
     """Mocked AWS Credentials for moto."""
-    environ["AWS_ACCESS_KEY_ID"] = "testing"
-    environ["AWS_SECRET_ACCESS_KEY"] = "testing"
-    environ["AWS_SECURITY_TOKEN"] = "testing"
-    environ["AWS_SESSION_TOKEN"] = "testing"
+    monkeypatch.setenv("AWS_ACCESS_KEY_ID", "testing")
+    monkeypatch.setenv("AWS_SECRET_ACCESS_KEY", "testing")
+    monkeypatch.setenv("AWS_SECURITY_TOKEN", "testing")
+    monkeypatch.setenv("AWS_SESSION_TOKEN", "testing")
 
 
 @pytest.fixture(scope="function")
diff --git a/tests/test_efs/test_mount_target_security_groups.py b/tests/test_efs/test_mount_target_security_groups.py
index 7f6fb1798..05fc2ee2f 100644
--- a/tests/test_efs/test_mount_target_security_groups.py
+++ b/tests/test_efs/test_mount_target_security_groups.py
@@ -1,5 +1,3 @@
-from os import environ
-
 import boto3
 import pytest
 from botocore.exceptions import ClientError
@@ -8,12 +6,12 @@ from moto import mock_ec2, mock_efs
 
 
 @pytest.fixture(scope="function")
-def aws_credentials():
+def aws_credentials(monkeypatch):
     """Mocked AWS Credentials for moto."""
-    environ["AWS_ACCESS_KEY_ID"] = "testing"
-    environ["AWS_SECRET_ACCESS_KEY"] = "testing"
-    environ["AWS_SECURITY_TOKEN"] = "testing"
-    environ["AWS_SESSION_TOKEN"] = "testing"
+    monkeypatch.setenv("AWS_ACCESS_KEY_ID", "testing")
+    monkeypatch.setenv("AWS_SECRET_ACCESS_KEY", "testing")
+    monkeypatch.setenv("AWS_SECURITY_TOKEN", "testing")
+    monkeypatch.setenv("AWS_SESSION_TOKEN", "testing")
 
 
 @pytest.fixture(scope="function")
diff --git a/tests/test_efs/test_server.py b/tests/test_efs/test_server.py
index 2670a3f5d..207280d82 100644
--- a/tests/test_efs/test_server.py
+++ b/tests/test_efs/test_server.py
@@ -1,6 +1,4 @@
 import re
-from os import environ
-
 import pytest
 
 from moto import mock_efs, mock_ec2
@@ -12,12 +10,12 @@ MOUNT_TARGETS = "/2015-02-01/mount-targets"
 
 
 @pytest.fixture(scope="function")
-def aws_credentials():
+def aws_credentials(monkeypatch):
     """Mocked AWS Credentials for moto."""
-    environ["AWS_ACCESS_KEY_ID"] = "testing"
-    environ["AWS_SESSION_TOKEN"] = "testing"
-    environ["AWS_SECRET_ACCESS_KEY"] = "testing"
-    environ["AWS_SECURITY_TOKEN"] = "testing"
+    monkeypatch.setenv("AWS_ACCESS_KEY_ID", "testing")
+    monkeypatch.setenv("AWS_SECRET_ACCESS_KEY", "testing")
+    monkeypatch.setenv("AWS_SECURITY_TOKEN", "testing")
+    monkeypatch.setenv("AWS_SESSION_TOKEN", "testing")
 
 
 @pytest.fixture(scope="function")