diff --git a/tests/app/test_configuration.py b/tests/app/test_configuration.py
index f05924d6..2719df23 100644
--- a/tests/app/test_configuration.py
+++ b/tests/app/test_configuration.py
@@ -161,8 +161,6 @@ def test_smtp_bad_tls(testclient, backend, smtpd, configuration):
 
 @pytest.fixture
 def themed_testclient(app, configuration, backend):
-    configuration["TESTING"] = True
-
     root = os.path.dirname(os.path.abspath(__file__))
     test_theme_path = os.path.join(root, "fixtures", "themes", "test")
     configuration["CANAILLE"]["THEME"] = test_theme_path
diff --git a/tests/app/test_logging.py b/tests/app/test_logging.py
index 3d670f4f..49312792 100644
--- a/tests/app/test_logging.py
+++ b/tests/app/test_logging.py
@@ -31,7 +31,6 @@ format=[%(asctime)s] %(levelname)s in %(module)s: %(message)s
 
 
 def test_file_log_config(configuration, backend, tmp_path, smtpd, admin):
-    configuration["TESTING"] = True
     assert len(smtpd.messages) == 0
     log_path = os.path.join(tmp_path, "canaille-by-file.log")
 
@@ -63,7 +62,6 @@ def test_file_log_config(configuration, backend, tmp_path, smtpd, admin):
 
 
 def test_dict_log_config(configuration, backend, tmp_path, smtpd, admin):
-    configuration["TESTING"] = True
     assert len(smtpd.messages) == 0
     log_path = os.path.join(tmp_path, "canaille-by-dict.log")
     configuration["CANAILLE"]["LOGGING"] = {
diff --git a/tests/conftest.py b/tests/conftest.py
index d76bc331..3cdd656e 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -68,6 +68,7 @@ def configuration(smtpd):
         "SECRET_KEY": gen_salt(24),
         "SERVER_NAME": "canaille.test",
         "PREFERRED_URL_SCHEME": "http",
+        "TESTING": True,
         "CANAILLE": {
             "JAVASCRIPT": False,
             "LOGO": "/static/img/canaille-head.webp",
@@ -174,7 +175,6 @@ def app(configuration, backend, jinja_cache_directory):
 
 @pytest.fixture
 def testclient(app):
-    app.config["TESTING"] = True
     app.jinja_env.undefined = StrictUndefined
     yield TestApp(app)