ExpenseTracker API

Flask + PostgreSQL expense tracking API with JWT authentication, user-scoped expense CRUD, and pytest test layers (unit, integration, end-to-end).

Features

• User signup and login
• JWT-based authorization (Authorization: Bearer <token>)
• Expense CRUD scoped to the authenticated user
• Expense listing with date filters (week, month, 3months, custom)
• Defensive input validation for malformed JSON, missing fields, and invalid query params

Requirements

• Python 3.13+
• PostgreSQL

Installation

python -m venv .venv
source .venv/bin/activate
pip install -r requirements.txt

Configuration

1. Create .env in project root:

SECRET_JWT=your-strong-secret

2. Update config/database.ini with your PostgreSQL credentials:

[postgresql]
host=localhost
dbname=mydb
user=your_user
password=your_password
port=5432

Initialize Database

python database/database.py

This creates:

• users
• categories
• expenses

Run API

flask --app app run --debug

Default local URL: http://127.0.0.1:5000

API Endpoints

Auth

• POST /signup
• POST /login
  • Returns: {"token": "<jwt>"} on success

JWT usage for protected routes:

Authorization: Bearer <jwt>

Expenses (auth required)

• GET /expenses
  • Query params:
    • filter=week|month|3months|custom
    • start_date=YYYY-MM-DD (custom only)
    • end_date=YYYY-MM-DD (custom only)
    • limit=<positive integer>
• POST /expenses
  • Required JSON fields: cost, category_id
  • Optional JSON fields: description
• PUT /expenses/<expense_id>
  • Optional JSON fields: cost, category_id, description
  • Omitted fields keep their existing DB values (partial update behavior)
• DELETE /expenses/<expense_id>

Error Behavior

The API returns structured errors:

{"error": "..."}

or field-level details:

{"error": {"field_name": "message"}}

Common status codes:

• 400 validation errors
• 401 authentication errors
• 403 authorization errors
• 404 not found
• 409 conflict (e.g., duplicate username/email)

Tests (pytest)

Test structure:

• tests/unit — service and utility logic
• tests/integration — repository behavior and query construction
• tests/e2e — API route behavior with Flask test client

Run all tests:

python -m pytest -q

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Project idea by Roadmap.sh