diff --git a/src/users.py b/src/users.py
index 2a888e8..6075be8 100644
--- a/src/users.py
+++ b/src/users.py
@@ -24,9 +24,9 @@ def combine_user_lists(server_1_users, server_2_users, user_mapping):
 
     for server_1_user in server_1_users:
         if user_mapping:
-            jellyfin_plex_mapped_user = search_mapping(user_mapping, server_1_user)
-            if jellyfin_plex_mapped_user:
-                users[server_1_user] = jellyfin_plex_mapped_user
+            mapped_user = search_mapping(user_mapping, server_1_user)
+            if mapped_user in server_2_users:
+                users[server_1_user] = mapped_user
                 continue
 
         if server_1_user in server_2_users:
@@ -34,9 +34,9 @@ def combine_user_lists(server_1_users, server_2_users, user_mapping):
 
     for server_2_user in server_2_users:
         if user_mapping:
-            plex_jellyfin_mapped_user = search_mapping(user_mapping, server_2_user)
-            if plex_jellyfin_mapped_user:
-                users[plex_jellyfin_mapped_user] = server_2_user
+            mapped_user = search_mapping(user_mapping, server_2_user)
+            if mapped_user in server_1_users:
+                users[mapped_user] = server_2_user
                 continue
 
         if server_2_user in server_1_users:
diff --git a/test/test_users.py b/test/test_users.py
new file mode 100644
index 0000000..fc3785b
--- /dev/null
+++ b/test/test_users.py
@@ -0,0 +1,39 @@
+import sys
+import os
+
+# getting the name of the directory
+# where the this file is present.
+current = os.path.dirname(os.path.realpath(__file__))
+
+# Getting the parent directory name
+# where the current directory is present.
+parent = os.path.dirname(current)
+
+# adding the parent directory to
+# the sys.path.
+sys.path.append(parent)
+
+from src.users import (
+    combine_user_lists,
+    filter_user_lists,
+)
+
+
+def test_combine_user_lists():
+    server_1_users = ["test", "test3", "luigi311"]
+    server_2_users = ["luigi311", "test2", "test3"]
+    user_mapping = {"test2": "test"}
+
+    combined = combine_user_lists(server_1_users, server_2_users, user_mapping)
+
+    assert combined == {"luigi311": "luigi311", "test": "test2", "test3": "test3"}
+
+
+def test_filter_user_lists():
+    users = {"luigi311": "luigi311", "test": "test2", "test3": "test3"}
+    blacklist_users = ["test3"]
+    whitelist_users = ["test", "luigi311"]
+
+    filtered = filter_user_lists(users, blacklist_users, whitelist_users)
+
+    assert filtered == {"test": "test2", "luigi311": "luigi311"}