💰 Expense Tracker

A simple, elegant expense tracking application built with Flask. Track your spending, categorize expenses, and stay on budget.

Features

• ✅ Add, view, and delete expenses
• 📊 Filter expenses by category
• 💵 Real-time total calculation
• 📱 Responsive design
• 🔌 REST API endpoints
• ✨ Clean, modern UI
• 🧪 Comprehensive test suite

Project Structure

expense-tracker/
├── app.py                  # Main Flask application
├── test_app.py             # Pytest test suite
├── requirements.txt        # Python dependencies
├── templates/
│   └── index.html         # Main HTML template
├── static/
│   └── css/
│       └── style.css      # CSS styles
└── README.md              # This file

Requirements

• Python 3.8 or higher
• pip (Python package manager)

Installation

1. Clone or download this repository

2. Navigate to the project directory

   cd expense-tracker

3. Install dependencies

   pip install -r requirements.txt

Running the Application

1. Start the Flask development server

   python app.py

2. Open your browser and visit

   http://localhost:5000
   

3. Start tracking your expenses!

Running the Tests

The application includes a comprehensive test suite using pytest.

Run all tests:

pytest test_app.py -v

Run specific test classes:

# Test only the Expense class
pytest test_app.py::TestExpenseClass -v

# Test only the routes
pytest test_app.py::TestRoutes -v

# Test only the API
pytest test_app.py::TestAPI -v

Run with coverage:

pip install pytest-cov
pytest test_app.py --cov=app --cov-report=html

Expected test output:

test_app.py::TestExpenseClass::test_expense_creation PASSED
test_app.py::TestExpenseClass::test_expense_with_date PASSED
test_app.py::TestRoutes::test_index_route PASSED
test_app.py::TestRoutes::test_add_expense_success PASSED
...
======================== XX passed in X.XXs ========================

Using the Application

Adding an Expense

1. Fill in the amount, category, description, and date
2. Click "Add Expense"
3. Your expense will appear in the list below

Filtering Expenses

• Use the dropdown menu to filter by category
• Select "All Categories" to view all expenses

Deleting an Expense

• Click the "Delete" button next to any expense
• Confirm the deletion

Clearing All Expenses

• Click "Clear All Expenses" at the bottom
• Confirm to remove all data

API Endpoints

The application provides REST API endpoints for programmatic access:

Get All Expenses

GET /api/expenses

Response:

[
  {
    "id": 1,
    "amount": 50.00,
    "category": "Food & Dining",
    "description": "Lunch",
    "date": "2024-02-09"
  }
]

Get Summary

GET /api/summary

Response:

{
  "by_category": {
    "Food & Dining": 75.50,
    "Transportation": 30.00
  },
  "total": 105.50,
  "count": 3
}

Categories

The application supports the following expense categories:

• 🍔 Food & Dining
• 🚗 Transportation
• 🛍️ Shopping
• 🎬 Entertainment
• 💡 Bills & Utilities
• 🏥 Healthcare
• 📦 Other

Data Storage

Currently, the application uses in-memory storage. This means:

• ✅ Fast and simple
• ❌ Data is lost when the server restarts
• 💡 Future enhancement: Add SQLite or PostgreSQL for persistence

Testing Strategy

The test suite covers:

1. Unit Tests - Testing the Expense class
2. Route Tests - Testing Flask endpoints
3. API Tests - Testing JSON API responses
4. Integration Tests - Testing complete workflows
5. Validation Tests - Testing input validation and error handling

Test Coverage Includes:

• ✅ Expense creation and validation
• ✅ Adding expenses (valid and invalid inputs)
• ✅ Deleting expenses
• ✅ Filtering by category
• ✅ Total calculation
• ✅ API responses
• ✅ Error handling
• ✅ Complete user workflows

Development Notes

Built With

• Flask - Python web framework
• pytest - Testing framework
• HTML/CSS - Frontend (no JavaScript frameworks needed!)

Code Generation Tool Used

This project was built using Claude (Anthropic's AI assistant) to demonstrate effective use of AI code generation tools for rapid application development.

Key Engineering Practices

• ✅ Clean, readable code with comments
• ✅ Comprehensive test coverage
• ✅ Input validation and error handling
• ✅ RESTful API design
• ✅ Responsive UI design
• ✅ Clear documentation

Future Enhancements

Potential improvements for the application:

• Persistent storage (SQLite/PostgreSQL)
• User authentication
• Budget setting and alerts
• Monthly/weekly summaries
• Data export (CSV, PDF)
• Charts and visualizations
• Receipt image uploads
• Recurring expense tracking

Troubleshooting

Port Already in Use

If port 5000 is already in use, modify app.py:

app.run(debug=True, host='0.0.0.0', port=5001)  # Change port

Module Not Found Errors

Make sure you've installed all dependencies:

pip install -r requirements.txt

Tests Failing

Ensure you're in the correct directory and have pytest installed:

pip install pytest
pytest test_app.py -v

License

This project is provided as-is for educational and demonstration purposes.

Contributing

This is a demonstration project, but feel free to fork and modify for your own use!

Contact

For questions or feedback about this project, please reach out through the repository.

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Happy expense tracking! 💰