diff --git a/.gitignore b/.gitignore
index 9500af4..a354bcc 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,6 +4,17 @@ __pycache__/
 *.pyo
 *.pyd
 .Python
+env/
+venv/
+ENV/
+env.bak/
+venv.bak/
+.vscode/
+.pytest_cache/
+instance/
+*.db
+*.sqlite
+*.sqlite3
 *.so
 *.egg
 *.egg-info/
@@ -12,4 +23,9 @@ build/
 instance/*.db
 .env
 .DS_Store
-*.log
\ No newline at end of file
+*.log
+.pytest_cache/
+.coverage
+htmlcov/
+.tox/
+.cache/
diff --git a/README.md b/README.md
index 0146ecd..d8f45e7 100644
--- a/README.md
+++ b/README.md
@@ -36,6 +36,35 @@ Set a coding goal, set a deadline, and watch the countdown tick. The timer only
 4. **Open locally in your browser**:
    Navigate to `http://localhost:5000`
 
+## Testing
+
+The project includes automated tests using pytest to ensure code quality and prevent regressions.
+
+### Running Tests
+
+1. **Install test dependencies** (included in requirements.txt):
+   ```bash
+   pip install -r requirements.txt
+   ```
+
+2. **Run the test suite**:
+   ```bash
+   pytest
+   ```
+
+3. **Run tests with coverage**:
+   ```bash
+   pytest --cov=application --cov-report=html
+   ```
+
+### Test Structure
+
+- `tests/test_api.py`: API endpoint tests (health check, etc.)
+- `tests/test_models.py`: Model unit tests (Goal.to_dict(), etc.)
+- `tests/conftest.py`: Shared fixtures for Flask app and database setup
+
+Tests use an in-memory SQLite database for isolation and speed.
+
 ## Usage
 
 1. **Login with GitHub** - Authenticate via OAuth2
diff --git a/pytest.ini b/pytest.ini
new file mode 100644
index 0000000..3a0c46d
--- /dev/null
+++ b/pytest.ini
@@ -0,0 +1,6 @@
+[tool:pytest]
+testpaths = tests
+python_files = test_*.py
+python_classes = Test*
+python_functions = test_*
+addopts = -v --tb=short
\ No newline at end of file
diff --git a/requirements.txt b/requirements.txt
index 8341ecf..505431a 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -4,3 +4,6 @@ requests
 python-dotenv
 gunicorn
 psycopg2-binary
+pytest>=7.4.0
+pytest-flask
+pytest-cov
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/conftest.py b/tests/conftest.py
new file mode 100644
index 0000000..b5df69f
--- /dev/null
+++ b/tests/conftest.py
@@ -0,0 +1,38 @@
+import pytest
+import os
+
+# Set test environment variables before importing application
+os.environ['DATABASE_URL'] = 'sqlite:///:memory:'
+os.environ['SECRET_KEY'] = 'test-secret-key'
+os.environ['BASE_URL'] = 'http://localhost:5000'
+
+from application import application, db
+
+@pytest.fixture(scope='session')
+def app():
+    """Create and configure a test app instance."""
+    # App is already configured with test settings
+    test_app = application
+
+    # Create database tables
+    with test_app.app_context():
+        db.create_all()
+
+    yield test_app
+
+@pytest.fixture(scope='session')
+def client(app):
+    """A test client for the app."""
+    return app.test_client()
+
+@pytest.fixture(scope='function')
+def session(app):
+    """Create a new database session for a test."""
+    with app.app_context():
+        # Start a transaction
+        db.session.begin_nested()
+
+        yield db.session
+
+        # Rollback the transaction after the test
+        db.session.rollback()
\ No newline at end of file
diff --git a/tests/test_api.py b/tests/test_api.py
new file mode 100644
index 0000000..aa78463
--- /dev/null
+++ b/tests/test_api.py
@@ -0,0 +1,29 @@
+import json
+from datetime import datetime
+
+def test_health_endpoint(client):
+    """Test the /api/health endpoint returns healthy status."""
+    response = client.get('/api/health')
+
+    # Check status code
+    assert response.status_code == 200
+
+    # Parse JSON response
+    data = json.loads(response.data)
+
+    # Check required fields are present
+    assert 'status' in data
+    assert 'timestamp' in data
+    assert 'service' in data
+
+    # Check status is healthy
+    assert data['status'] == 'healthy'
+
+    # Check service name
+    assert data['service'] == 'git-done-api'
+
+    # Check timestamp is valid ISO format
+    try:
+        datetime.fromisoformat(data['timestamp'])
+    except ValueError:
+        pytest.fail("Timestamp is not in valid ISO format")
\ No newline at end of file
diff --git a/tests/test_models.py b/tests/test_models.py
new file mode 100644
index 0000000..7e75cd5
--- /dev/null
+++ b/tests/test_models.py
@@ -0,0 +1,108 @@
+import pytest
+from datetime import datetime, timedelta, UTC
+from application import Goal
+
+def test_goal_to_dict_required_fields(session):
+    """Test Goal.to_dict() with all required fields."""
+    # Create a test goal
+    deadline = datetime.now(UTC) + timedelta(days=7)
+    goal = Goal(
+        user_github_id='12345',
+        description='Test goal',
+        deadline=deadline,
+        repo_url='https://github.com/user/repo',
+        completion_condition='fix bug',
+        status='active',
+        repo_owner='user',
+        repo_name='repo',
+        embed_token='test-token'
+    )
+    session.add(goal)
+    session.commit()
+
+    result = goal.to_dict()
+
+    # Check all expected fields are present
+    expected_fields = [
+        'id', 'user_github_id', 'description', 'deadline', 'repo_url',
+        'completion_condition', 'status', 'created_at', 'embed_token', 'embed_url'
+    ]
+
+    for field in expected_fields:
+        assert field in result, f"Missing field: {field}"
+
+    # Check data types
+    assert isinstance(result['id'], int)
+    assert isinstance(result['user_github_id'], str)
+    assert isinstance(result['description'], str)
+    assert isinstance(result['deadline'], str)
+    assert isinstance(result['repo_url'], str)
+    assert isinstance(result['completion_condition'], str)
+    assert isinstance(result['status'], str)
+    assert isinstance(result['created_at'], str)
+    assert isinstance(result['embed_token'], str)
+    assert isinstance(result['embed_url'], str)
+
+    # Check datetime serialization
+    try:
+        datetime.fromisoformat(result['deadline'])
+        datetime.fromisoformat(result['created_at'])
+    except ValueError as e:
+        pytest.fail(f"Invalid datetime format: {e}")
+
+    # Check embed_url format
+    assert result['embed_url'] == 'http://localhost:5000/embed/test-token'
+
+def test_goal_to_dict_with_completed_at(session):
+    """Test Goal.to_dict() with completed_at field."""
+    deadline = datetime.now(UTC) + timedelta(days=7)
+    completed_at = datetime.now(UTC)
+    goal = Goal(
+        user_github_id='12345',
+        description='Completed goal',
+        deadline=deadline,
+        repo_url='https://github.com/user/repo',
+        completion_condition='fix bug',
+        status='completed',
+        completed_at=completed_at,
+        repo_owner='user',
+        repo_name='repo',
+        embed_token='test-token-completed'
+    )
+    session.add(goal)
+    session.commit()
+
+    result = goal.to_dict()
+
+    # Check completed_at is serialized
+    assert 'completed_at' in result
+    assert result['completed_at'] is not None
+    assert isinstance(result['completed_at'], str)
+
+    # Check it's valid ISO format
+    try:
+        datetime.fromisoformat(result['completed_at'])
+    except ValueError as e:
+        pytest.fail(f"Invalid completed_at datetime format: {e}")
+
+def test_goal_to_dict_without_embed_token(session):
+    """Test Goal.to_dict() without embed_token."""
+    deadline = datetime.now(UTC) + timedelta(days=7)
+    goal = Goal(
+        user_github_id='12345',
+        description='Goal without embed token',
+        deadline=deadline,
+        repo_url='https://github.com/user/repo',
+        completion_condition='fix bug',
+        status='active',
+        repo_owner='user',
+        repo_name='repo'
+    )
+    session.add(goal)
+    session.commit()
+
+    result = goal.to_dict()
+
+    # Check embed_token and embed_url are None
+    assert result['embed_token'] is None
+    assert result['embed_url'] is None
\ No newline at end of file