diff --git a/.github/workflows/run-tests.yml b/.github/workflows/run-tests.yml
new file mode 100644
index 0000000..555ce89
--- /dev/null
+++ b/.github/workflows/run-tests.yml
@@ -0,0 +1,34 @@
+name: Run Flask Backend Tests
+
+# Trigger on PRs to master
+on:
+  pull_request:
+    branches:
+      - master
+
+jobs:
+  tests:
+    runs-on: ubuntu-latest
+
+    steps:
+      # Step 1: Checkout repo
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      # Step 2: Set up Python
+      - name: Set up Python 3.11
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
+
+      # Step 3: Install dependencies
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install -r backend/requirements.txt
+
+      # Step 4: Run tests
+      - name: Run pytest
+        working-directory: backend
+        run: |
+          pytest -v
\ No newline at end of file
diff --git a/backend/__init__.py b/backend/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/backend/app.py b/backend/app.py
index a32ca96..6a2ef72 100644
--- a/backend/app.py
+++ b/backend/app.py
@@ -1,17 +1,23 @@
-from config import Config
-from extensions import db, jwt, migrate
+from backend.config import Config
+from backend.extensions import db, jwt, migrate
 from flask import Flask
 
 
-def create_app():
+def create_app(config_object=None):
     app = Flask(__name__)
+
+    # Default config
     app.config.from_object(Config)
 
+    # Override config (for tests)
+    if config_object:
+        app.config.update(config_object)
+
     db.init_app(app)
     jwt.init_app(app)
     migrate.init_app(app, db)
 
-    from routes.auth_routes import auth_bp
+    from backend.routes.auth_routes import auth_bp
 
     app.register_blueprint(auth_bp)
 
diff --git a/backend/models/user.py b/backend/models/user.py
index cb96997..014f866 100644
--- a/backend/models/user.py
+++ b/backend/models/user.py
@@ -1,7 +1,7 @@
 import string
 import uuid
 
-from extensions import db
+from backend.extensions import db
 from werkzeug.security import check_password_hash, generate_password_hash
 
 
diff --git a/backend/models/user_stats.py b/backend/models/user_stats.py
index 9391406..80a7cf3 100644
--- a/backend/models/user_stats.py
+++ b/backend/models/user_stats.py
@@ -1,4 +1,4 @@
-from extensions import db
+from backend.extensions import db
 
 
 class UserStats(db.Model):
diff --git a/backend/requirements.txt b/backend/requirements.txt
index 1056346..3e91890 100644
--- a/backend/requirements.txt
+++ b/backend/requirements.txt
@@ -3,11 +3,13 @@ black==25.11.0
 blinker==1.9.0
 click==8.1.8
 colorama==0.4.6
+exceptiongroup==1.3.1
 Flask==3.1.2
 Flask-JWT-Extended==4.7.1
 Flask-Migrate==4.1.0
 Flask-SQLAlchemy==3.1.1
 importlib_metadata==8.7.1
+iniconfig==2.1.0
 itsdangerous==2.2.0
 Jinja2==3.1.6
 Mako==1.3.10
@@ -16,7 +18,12 @@ mypy_extensions==1.1.0
 packaging==26.0
 pathspec==1.0.4
 platformdirs==4.4.0
+pluggy==1.6.0
+psycopg2-binary==2.9.11
+Pygments==2.19.2
 PyJWT==2.10.1
+pytest==8.4.2
+pytest-flask==1.3.0
 python-dotenv==1.2.1
 pytokens==0.4.1
 SQLAlchemy==2.0.46
@@ -24,4 +31,3 @@ tomli==2.4.0
 typing_extensions==4.15.0
 Werkzeug==3.1.5
 zipp==3.23.0
-psycopg2-binary
diff --git a/backend/routes/auth_routes.py b/backend/routes/auth_routes.py
index 6c98fb2..a41ecd4 100644
--- a/backend/routes/auth_routes.py
+++ b/backend/routes/auth_routes.py
@@ -1,8 +1,8 @@
 import logging
-from extensions import db
+from backend.extensions import db
 from flask import Blueprint, jsonify, request
-from models.user import User
-from models.user_stats import UserStats
+from backend.models.user import User
+from backend.models.user_stats import UserStats
 from werkzeug.security import generate_password_hash
 
 # Auth Blueprint
diff --git a/backend/tests/__init__.py b/backend/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/backend/tests/conftest.py b/backend/tests/conftest.py
new file mode 100644
index 0000000..ab5c239
--- /dev/null
+++ b/backend/tests/conftest.py
@@ -0,0 +1,32 @@
+import json
+import pytest
+from backend.app import create_app
+from backend.extensions import db
+
+
+@pytest.fixture(scope="session")
+def test_data():
+    with open("tests/data/users.json") as f:
+        return json.load(f)
+
+
+@pytest.fixture
+def app():
+    app = create_app(
+        {
+            "TESTING": True,
+            "SQLALCHEMY_DATABASE_URI": "sqlite:///:memory:",
+            "SQLALCHEMY_TRACK_MODIFICATIONS": False,
+        }
+    )
+
+    with app.app_context():
+        db.create_all()
+        yield app
+        db.session.remove()
+        db.drop_all()
+
+
+@pytest.fixture
+def client(app):
+    return app.test_client()
diff --git a/backend/tests/data/users.json b/backend/tests/data/users.json
new file mode 100644
index 0000000..10f9760
--- /dev/null
+++ b/backend/tests/data/users.json
@@ -0,0 +1,17 @@
+{
+    "valid_user": {
+      "username": "testuser",
+      "email": "testuser@example.com",
+      "password": "StrongP@ssw0rd"
+    },
+    "weak_password": {
+      "username": "weakuser",
+      "email": "weak@example.com",
+      "password": "weak"
+    },
+    "missing_fields": {
+      "username": "",
+      "email": "missing@example.com",
+      "password": ""
+    }
+  }
\ No newline at end of file
diff --git a/backend/tests/test_auth_register.py b/backend/tests/test_auth_register.py
new file mode 100644
index 0000000..d8108ae
--- /dev/null
+++ b/backend/tests/test_auth_register.py
@@ -0,0 +1,30 @@
+def test_register_success(client, test_data):
+    res = client.post("/register", json=test_data["valid_user"])
+
+    assert res.status_code == 201
+    data = res.get_json()
+    assert "User registered successfully" in data["msg"]
+
+
+def test_register_weak_password(client, test_data):
+    res = client.post("/register", json=test_data["weak_password"])
+
+    assert res.status_code == 400
+    data = res.get_json()
+    assert "password" in data["error"].lower()
+
+
+def test_register_missing_fields(client, test_data):
+    res = client.post("/register", json=test_data["missing_fields"])
+
+    assert res.status_code == 400
+
+
+def test_register_duplicate_username(client, test_data):
+    client.post("/register", json=test_data["valid_user"])
+
+    res = client.post(
+        "/register", json={**test_data["valid_user"], "email": "another@example.com"}
+    )
+
+    assert res.status_code == 409