Mock Payment System with Automated Cart and Checkout Flow 🚀

This project provides a complete payment flow simulation using two FastAPI services:

1. Cart Service: Handles item additions and initiates the checkout process.
   URL: http://localhost:8001
2. Payment Server: Processes payments and sends webhook notifications.
   URL: http://localhost:8000

The flow mimics a real-world e-commerce payment process with these steps:

• Adding items to a cart.
• Initiating a checkout and sending a payment request.
• Capturing the payment.
• Sending and receiving a webhook notification.

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Prerequisites

1. Python 3.9 or higher
2. Install the following Python packages:

   pip install fastapi uvicorn requests

3. Install jq for JSON parsing:
   • Ubuntu/Debian:

     sudo apt-get install jq

   • macOS:

     brew install jq

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Usage Instructions

1. Clone the Repository:

   git clone https://github.com/r74tech/dummy-payment.git
   cd dummy-payment

2. Start the Cart Service:

   uvicorn cart_service:app --reload --port 8001

3. Ensure the Payment Server is Running:

   • If not already running, start it on port 8000:

     docker compose up -d --build

4. Run the Payment Flow Script: Make sure both services are running, then execute the script to test the complete flow:

   ./run_payment_flow.sh

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Expected Output

=== Step 1: Get Access Token ===
Access Token: YHPGUNHOXHO3
=== Step 2: Add Item to Cart ===
Cart Response: {"msg":"Item item001 added to cart","cart":{"item001":{"quantity":2,"price":100.0}}}
=== Step 3: Start Checkout ===
Order ID: 2HXG07P5EU7R
Payment Token: YHPGUNHOXHO3
=== Payment Flow Completed Successfully ===

Docker Compose Logs:

INFO:     Started server process [8]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     Uvicorn running on http://0.0.0.0:8001 (Press CTRL+C to quit)
INFO:     Started server process [7]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     Uvicorn running on http://0.0.0.0:8000 (Press CTRL+C to quit)
INFO:     192.168.65.1:38645 - "POST /auth/token HTTP/1.1" 200 OK
INFO:     192.168.65.1:27506 - "POST /cart/add HTTP/1.1" 200 OK
INFO:     192.168.65.1:27507 - "POST /checkout HTTP/1.1" 200 OK
INFO:     127.0.0.1:53820 - "POST /payments/start HTTP/1.1" 200 OK
INFO:     127.0.0.1:53826 - "POST /payments/capture/YHPGUNHOXHO3 HTTP/1.1" 200 OK
INFO:     127.0.0.1:52438 - "POST /callback HTTP/1.1" 200 OK
Received Webhook: {'token': 'YHPGUNHOXHO3', 'transaction': {'status': 'captured', 'order_id': '2HXG07P5EU7R', 'amount': 200.0}}

sequenceDiagram
    participant User as User
    participant CartService as Cart Service (Port 8001)
    participant PaymentServer as Payment Server (Port 8000)

    User ->> CartService: POST /cart/add (item_id, quantity, price)
    CartService ->> User: Item added to cart (200 OK)

    User ->> CartService: POST /checkout (access-token: <token>)
    CartService ->> PaymentServer: POST /payments/start (order_id, amount, access-token)
    PaymentServer -->> CartService: Payment initiated (access_token)

    CartService ->> PaymentServer: POST /payments/capture/<access_token>
    PaymentServer -->> CartService: Payment captured successfully

    PaymentServer ->> CartService: POST /callback (token, transaction)
    CartService -->> PaymentServer: Webhook received successfully

Loading

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Troubleshooting

1. Verify Services:

   • Ensure both services are running on the correct ports:
     • Cart Service: http://localhost:8001
     • Payment Server: http://localhost:8000

2. Common Errors:

   • Connection Refused: Verify that the services are running.
   • jq not found: Install jq using the instructions above.

3. Check Logs:

   • Use logs from the services to debug any issues:

     tail -f uvicorn.log

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Project Overview

This project offers a full payment workflow simulation, from cart management to payment capture and webhook notifications. It’s ideal for:

• Testing e-commerce integrations
• Simulating payment flows for development and security exercises
• Mocking webhook handling scenarios

Feel free to extend this project with additional features like security challenges, error simulations, or support for additional payment methods.