diff --git a/app/core/__init__.py b/app/core/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/app/tests/__init__.py b/app/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/app/tests/test_backend.py b/app/tests/test_backend.py
new file mode 100644
index 0000000..30bbfff
--- /dev/null
+++ b/app/tests/test_backend.py
@@ -0,0 +1,61 @@
+import pytest
+
+from core.utils import sanitise_gamedata
+from backend.database import *
+
+
+def test_sanitise():
+    control_game_mode = "city"
+    control_usern = "testuser"
+    control_totalscore = 0
+
+    # TEST THE GAME MODE VALIDITY
+    valid_gamemodes = ["city", "discoveries", "sleuth", "landmark"]
+    for game in valid_gamemodes:
+        assert sanitise_gamedata(game, control_usern, control_totalscore)[0] == game
+
+    invaid_gamemode = "THIS IS NOT A GAMEMODE"
+    assert sanitise_gamedata(invaid_gamemode, control_usern, control_totalscore)[0] == "city"
+
+    # TEST THE USERNAME VALIDITY
+    valid_usernames = ["testuser", "test.user", "test_user", "test_user_123."]
+    for username in valid_usernames:
+        assert sanitise_gamedata(control_game_mode, username, control_totalscore)[1] == username
+
+    invalid_username = "f@ucky!ou"
+    assert sanitise_gamedata(control_game_mode, invalid_username, control_totalscore)[1] == "fuckyou"
+
+    # TEST TOTALSORE VALIDITY
+    valid_totalscores = [0, 2000, 300, 3043]
+    for score in valid_totalscores:
+        assert sanitise_gamedata(control_game_mode, control_usern, score)[2] == score
+
+    invalid_totalscore = "piss" #string is an invalid total score
+    assert sanitise_gamedata(control_game_mode, control_usern, invalid_totalscore)[2] == 0
+
+def test_new_leaderboard_entry():
+
+    valid_username = "TEST_USERNAME_DB"
+    valid_gamemode = 'city'
+    valid_totalscore = 500
+
+    opt = update_game(valid_gamemode, valid_username, valid_totalscore)
+
+    assert opt == {"score":"complete", "alert":"no new high score"}
+
+    existing_username = "pinpoint_bot"
+    new_highscore = 500
+    assert update_game(valid_gamemode, existing_username, new_highscore) == {"score":"complete", "alert":"new high score"}
+
+    existing_username = "pinpoint_bot"
+    new_score = 400
+    assert update_game(valid_gamemode, existing_username, new_score) == {"score":"complete", "alert":"no new high score"}   
+    
+
+
+
+
+
+
+    
+
diff --git a/requirements.txt b/requirements.txt
index 319f2b8..7822015 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,5 @@
 fastapi
 uvicorn
 jinja2
-requests
\ No newline at end of file
+requests
+pytest
\ No newline at end of file
diff --git a/test_backend.py b/test_backend.py
new file mode 100644
index 0000000..00e2010
--- /dev/null
+++ b/test_backend.py
@@ -0,0 +1,16 @@
+from app.core.utils import sanitise_gamedata
+
+import pytest
+
+def test_sanitise():
+    control_game_mode = "city"
+    control_usern = "testuser"
+    control_totalscore = 0
+
+    results = None
+
+    # TEST THE GAME MODE VALIDITY
+    valid_gamemodes = ["city", "discoveries", "sleuth", "landmark"]
+    for game in valid_gamemodes:
+        assert sanitise_gamedata(game, control_usern, control_totalscore) == results[0]
+    
\ No newline at end of file