Banking System Mock API

A Node.js + TypeScript RESTful banking system with in-memory storage, JWT authentication, OpenAPI docs, and full test coverage.

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Project Structure

bankingSystemMock/
├── src/
│   ├── app.ts                # Express app and middleware
│   ├── server.ts             # Server entry point
│   ├── models/
│   │   └── Account.ts        # Type definitions
│   ├── routes/
│   │   └── bankingRoutes.ts  # All API routes
│   └── services/
│       └── BankingService.ts # Business logic (atomic operations)
├── tests/
│   └── banking.test.ts       # Jest unit and integration tests
├── postman/
│   └── Banking System Mock API.postman_collection.json # Postman collection
├── openapi.yaml              # OpenAPI 3.1 spec
├── Dockerfile                # Docker build config
├── .dockerignore
├── package.json
└── README.md

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Features

• Account Management

  • Create account (unique name, non-negative balance)
  • List all accounts
  • Get account by ID

• Transactions

  • Deposit (positive amount only)
  • Withdraw (cannot overdraw)
  • Transfer (atomic, cannot transfer to self, cannot overdraw)

• Transaction Logs

  • Get all transactions for an account
  • Get all transactions

• API Documentation

  • Swagger UI (JWT support)

• Security

  • JWT authentication (all /api routes require Bearer Token)
  • Helmet, rate-limit, unified error format

• Testing

  • Jest unit and integration tests, covers all edge cases

• Docker Support

  • One-command build/run, no need for local Node/npm

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Getting Started

1. Install dependencies

npm install

2. Set environment variables

Create a .env file (or use environment variables):

JWT_SECRET=6b2e1f9c-8a3d-4d7e-9c2a-7f1b2e3c4d5e

Note: This secret is for testing/demo only. In production, use a secure secret managed by your cloud platform or a Secret Manager.

3. Start development server

npm run dev

4. Run tests

npm test
npm run test:coverage

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Docker Deployment

Build & Run

docker build -t banking-system-mock .
docker run -p 9999:9999 --env JWT_SECRET=6b2e1f9c-8a3d-4d7e-9c2a-7f1b2e3c4d5e banking-system-mock

Note: This secret is for testing/demo only. In production, use environment variables or a Secret Manager.

Or use docker-compose

version: '3'
services:
  api:
    build: .
    ports:
      - "9999:9999"
    environment:
      - JWT_SECRET=your_secret

docker-compose up --build

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API Documentation

• Swagger UI: http://localhost:9999/docs
• OpenAPI YAML: openapi.yaml

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API Usage & Limitations

Authentication & Security

• All /api routes require Bearer Token (JWT). Use Authorization: Bearer <token> in the header.
• Invalid or missing JWT returns 401 Unauthorized.
• The default JWT_SECRET is for testing only. Always use a secure secret in production.

Rate Limiting

• Max 100 requests per minute (shared across all APIs). Exceeding this returns 429 Too Many Requests.
• See openapi.yaml and Swagger UI for 429 error examples.

Input Validation

• All amounts must be positive; account balances cannot be negative.
• Account names must be unique.
• Transfers cannot be to self (fromId ≠ toId), and source account must have sufficient balance.
• Request body only allows specified fields; extra fields will be rejected.

Response Format

• All API responses follow
  { success, data, error, message }
• On failure, success: false, error contains the error message, and data is null.

Data & Transaction Limitations

• All accounts and transactions are stored in memory; data is lost on server restart.
• No data persistence or multi-threaded deployment.
• No multi-currency, advanced permissions, or pagination (can be extended if needed).

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Postman Testing

1. Import postman/Banking System Mock API.postman_collection.json
2. Set the baseUrl variable to http://localhost:9999
3. Set the Bearer Token (the collection includes a demo token)

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Main API Endpoints

• POST /api/accounts Create account
• GET /api/accounts List all accounts
• GET /api/accounts/:id Get account by ID
• POST /api/accounts/:id/deposit Deposit
• POST /api/accounts/:id/withdraw Withdraw
• POST /api/accounts/transfer Transfer
• GET /api/accounts/:id/transactions Get account transaction logs
• GET /api/transactions Get all transactions

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Notes

• All data is in-memory and will be cleared on server restart.
• All API responses follow { success, data, error, message }