diff --git a/falcon/testing/test_case.py b/falcon/testing/test_case.py
index 632b662b7..1026adc86 100644
--- a/falcon/testing/test_case.py
+++ b/falcon/testing/test_case.py
@@ -18,18 +18,25 @@
 utilities for simulating and validating HTTP requests.
 """
 
-try:
-    import testtools as unittest
-except ImportError:  # pragma: nocover
-    import unittest
+import os
+import warnings
 
 import falcon
-import falcon.request
-
-# TODO hoist for backwards compat. Remove in falcon 4.
 from falcon.testing.client import Result  # NOQA
 from falcon.testing.client import TestClient
 
+USE_TESTTOOLS = os.getenv('USE_TESTTOOLS', 'false').lower() == 'true'
+
+try:
+    if USE_TESTTOOLS:
+        import testtools as unittest
+    else:
+        import unittest
+except ImportError:  # pragma: nocover
+    import unittest
+
+    USE_TESTTOOLS = False
+
 
 class TestCase(unittest.TestCase, TestClient):
     """Extends :mod:`unittest` to support WSGI/ASGI functional testing.
@@ -47,6 +54,12 @@ class TestCase(unittest.TestCase, TestClient):
     :class:`unittest.TestCase` or :class:`testtools.TestCase`.
     """
 
+    if USE_TESTTOOLS:
+        warnings.warn(
+            'The use of "testtools.TestCase" is deprecated and will be removed '
+            'in Falcon 5.0. Please migrate to "pytest" or "unittest" '
+        )
+
     # NOTE(vytas): Here we have to restore __test__ to allow collecting tests!
     __test__ = True
 
diff --git a/tests/test_testing.py b/tests/test_testing.py
index 89a8c49e8..fe1aa6319 100644
--- a/tests/test_testing.py
+++ b/tests/test_testing.py
@@ -1,3 +1,6 @@
+import os
+import warnings
+
 import pytest
 
 import falcon
@@ -224,3 +227,45 @@ def capture_method(req, resp):
     assert result.status_code == 200
     expected = '' if method == 'HEAD' else method
     assert result.text == expected
+
+
+def test_testclient_initialization():
+    class SampleResource:
+        def on_get(self, req, resp):
+            resp.media = {'message': 'Hello'}
+
+    class SampleTestCase(testing.TestCase):
+        def setUp(self):
+            super().setUp()
+            self.app = falcon.App()
+            self.app.add_route('/hello', SampleResource())
+
+    test_case = SampleTestCase()
+    test_case.setUp()
+    client = testing.TestClient(test_case.app)
+
+    response = client.simulate_get('/hello')
+    assert response.status_code == 200
+    assert response.json == {'message': 'Hello'}
+
+
+def test_deprecation_warning_with_testtools():
+    os.environ['USE_TESTTOOLS'] = 'true'
+
+    with warnings.catch_warnings(record=True) as w:
+        warnings.simplefilter('always')
+
+        class SampleTestCase(testing.TestCase):
+            def setUp(self):
+                super().setUp()
+                self.app = falcon.App()
+
+        test_case = SampleTestCase()
+        test_case.setUp()
+
+        assert any(
+            'The use of "testtools.TestCase" is deprecated' in str(warning.message)
+            for warning in w
+        ), 'Expected deprecation warning not found'
+
+    os.environ.pop('USE_TESTTOOLS', None)