diff --git a/tests/app/config_paths_test.py b/tests/app/config_paths_test.py
index e78d9f4ca..16730957d 100644
--- a/tests/app/config_paths_test.py
+++ b/tests/app/config_paths_test.py
@@ -8,8 +8,7 @@
 
 @pytest.fixture
 def voila_config_file_paths_arg():
-    os.path.join(BASE_DIR, "..", "configs", "general")
-    return "--VoilaTest.config_file_paths path"
+    return ["--VoilaTest.config_file_paths", os.path.join(BASE_DIR, "..", "configs", "general")]
 
 
 def test_config_app(voila_app):
diff --git a/tests/app/conftest.py b/tests/app/conftest.py
index 8f42b3219..e271f8623 100644
--- a/tests/app/conftest.py
+++ b/tests/app/conftest.py
@@ -25,7 +25,7 @@ def voila_args_extra():
 @pytest.fixture
 def voila_config_file_paths_arg():
     # we don't want the tests to use any configuration on the system
-    return ""
+    return []
 
 
 @pytest.fixture
@@ -35,7 +35,6 @@ def voila_args(voila_notebook, voila_args_extra, voila_config_file_paths_arg):
         if os.environ.get("VOILA_TEST_DEBUG", False)
         else []
     )
-    voila_config_file_paths_arg = [voila_config_file_paths_arg] if voila_config_file_paths_arg else []
     return [voila_notebook, *voila_config_file_paths_arg, *voila_args_extra, *debug_args]
 
 
diff --git a/tests/app/nbextensions_test.py b/tests/app/nbextensions_test.py
index 4211d9a94..3c7da6614 100644
--- a/tests/app/nbextensions_test.py
+++ b/tests/app/nbextensions_test.py
@@ -19,8 +19,7 @@ def config(app):
 @pytest.fixture
 def voila_config_file_paths_arg():
     # we don't want the tests to use any configuration on the system
-    os.path.abspath(os.path.join(BASE_DIR, "../configs/general"))
-    return "--VoilaTest.config_file_paths path"
+    return ["--VoilaTest.config_file_paths", os.path.abspath(os.path.join(BASE_DIR, "../configs/general"))]
 
 
 @pytest.mark.skip(reason="TODO: update for JupyterLab extensions")
diff --git a/tests/app/preheat_configuration_test.py b/tests/app/preheat_configuration_test.py
index 798e40908..6e1f750d8 100644
--- a/tests/app/preheat_configuration_test.py
+++ b/tests/app/preheat_configuration_test.py
@@ -12,8 +12,7 @@
 
 @pytest.fixture
 def voila_config_file_paths_arg():
-    os.path.join(BASE_DIR, "..", "configs", "preheat")
-    return "--VoilaTest.config_file_paths path"
+    return ["--VoilaTest.config_file_paths", os.path.join(BASE_DIR, "..", "configs", "preheat")]
 
 
 @pytest.fixture
diff --git a/tests/app/preheat_multiple_notebooks_test.py b/tests/app/preheat_multiple_notebooks_test.py
index 6ea34ccd4..f6bf48251 100644
--- a/tests/app/preheat_multiple_notebooks_test.py
+++ b/tests/app/preheat_multiple_notebooks_test.py
@@ -12,8 +12,7 @@
 
 @pytest.fixture
 def voila_config_file_paths_arg():
-    os.path.join(BASE_DIR, "..", "configs", "preheat")
-    return "--VoilaTest.config_file_paths path"
+    return ["--VoilaTest.config_file_paths", os.path.join(BASE_DIR, "..", "configs", "preheat")]
 
 
 @pytest.fixture