diff --git a/corres2math/lists.py b/corres2math/lists.py
index 187f4e2..9804ac6 100644
--- a/corres2math/lists.py
+++ b/corres2math/lists.py
@@ -8,6 +8,17 @@ _client = None
 def get_sympa_client() -> Client:
     global _client
     if _client is None:
-        _client = Client("https://" + os.getenv("SYMPA_URL"))
-        _client.login(os.getenv("SYMPA_EMAIL"), os.getenv("SYMPA_PASSWORD"))
+        if os.getenv("SYMPA_PASSWORD", None) is not None:
+            _client = Client("https://" + os.getenv("SYMPA_URL"))
+            _client.login(os.getenv("SYMPA_EMAIL"), os.getenv("SYMPA_PASSWORD"))
+        else:
+            _client = FakeSympaSoapClient()
     return _client
+
+
+class FakeSympaSoapClient:
+    """
+    Simulate a Sympa Soap client to run tests, if no Sympa instance is connected.
+    """
+    def __getattribute__(self, item):
+        return lambda *args, **kwargs: None