Streamlining Authentication Flows in Legacy Codebases with TypeScript Automation

In the realm of legacy systems, automating authentication flows presents unique challenges due to outdated architecture, sparse documentation, and mixed technology stacks. As a Lead QA Engineer, I faced these hurdles head-on, leveraging TypeScript to create reliable, scalable automation tests that ensure seamless user experiences across our authentication processes.

Identifying the Challenges

Legacy codebases often lack well-defined entry points for automation, making it difficult to simulate user interactions consistently. Additionally, authentication flows—such as login, password resets, and multi-factor authentication—are tightly coupled with older frameworks, complicating test development. Our goal was to build a robust, maintainable suite that could run reliably without invasive modifications to the existing system.

Choosing TypeScript for Automation

TypeScript provided us with static typing and modern language features, which increased confidence in our test scripts and reduced runtime errors. Its compatibility with existing JavaScript code and extensive ecosystem made it an ideal choice.

Setting Up the Environment

We began by integrating Playwright, which offers a Node.js API for browser automation with TypeScript support. Our setup involved installing the necessary packages:

npm install playwright typescript tsnode @types/node --save-dev

configuring tsconfig.json for compatibility with our legacy scripts.

{
  "compilerOptions": {
    "target": "ES6",
    "module": "commonjs",
    "strict": true,
    "esModuleInterop": true
  }
}

Building the Automation Scripts

The core of automating auth flows lies in simulating user interactions reliably, handling asynchronous events such as redirects, and managing session states.

Here's an example of a login automation script:

import { chromium, Page } from 'playwright';

async function login(page: Page, username: string, password: string) {
  await page.goto('https://legacyapp.example.com/login');
  await page.fill('#username', username);
  await page.fill('#password', password);
  await Promise.all([
    page.click('#loginButton'),
    page.waitForNavigation()
  ]);

  // Verify login success
  const loggedIn = await page.isVisible('#logoutButton');
  if (loggedIn) {
    console.log('Login successful');
  } else {
    console.error('Login failed');
  }
}

(async () => {
  const browser = await chromium.launch({ headless: true });
  const context = await browser.newContext();
  const page = await context.newPage();
  await login(page, 'testuser', 'Password123');
  await browser.close();
})();

Handling MFA or other complex flows often requires custom scripts to manage additional steps in the login process. Using TypeScript's type system, we can enforce input validation and reduce flaky tests.

Integrating with CI/CD Pipelines

Our automation scripts were integrated into the CI pipeline with Docker containers, ensuring consistent test execution environments and reducing environment-related flakiness.

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout code
        uses: actions/checkout@v2
      - name: Set up Node.js
        uses: actions/setup-node@v2
        with:
          node-version: '16'
      - name: Install dependencies
        run: |
          npm install
      - name: Run auth flow tests
        run: |
          npx ts-node tests/authflows.test.ts

Best Practices and Lessons Learned

• Resilience: Built waitForSelectors and error handling to make tests resilient to UI delays.
• Maintainability: Used environment variables and configuration files to manage credentials and URLs.
• Scalability: Modularized code to facilitate adding new auth tests, like password resets and MFA.

Conclusion

Automating complex auth flows in legacy codebases with TypeScript requires a strategic approach: understanding the system constraints, leveraging modern tooling, and designing reliable, maintainable scripts. By adopting TypeScript, we enhanced test robustness, reduced debugging time, and improved overall quality assurance processes.

This approach not only benefits immediate automation needs but also lays the groundwork for future modernization efforts in our legacy systems.

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🛠️ QA Tip

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