Overcoming Geo-Blocking in Feature Testing with TypeScript and Open Source Tools

#typescript #testing #opensource

In today's globalized software landscape, geo-restrictions and geolocation-based features pose significant challenges for testing and development. Particularly, testing geo-blocked features during continuous integration (CI) and local development remains a complex hurdle due to the difficulty in simulating different geographic locations reliably and efficiently.

As a Senior Developer and Architect, leveraging open source tools and TypeScript can streamline this process. This approach not only enhances test coverage but also ensures robust, location-agnostic deployment workflows.

Understanding the Challenge

Geo-blocked features depend on the user's geographic location, often identified via IP geolocation. When testing these features locally or in CI environments, the actual IP address used is usually the server's, which doesn't reflect different regions.

The challenge lies in simulating various locations without reliance on external VPNs or manual IP spoofing, which can be unreliable and hard to automate.

Leveraging open source tools

To address this, a combination of open source libraries like node-mock-ip for mocking geolocation, along with tools such as LocalStack or MockServer for API mocking and ts-mock for TypeScript-based test control, can effectively simulate different geo contexts.

Strategy: Mocking Geolocation in Tests

Here's a practical implementation outline:

Abstract Geolocation Access

Create an interface to fetch geolocation data, making it easy to swap between real and mocked data.

// geo.ts
export interface GeoLocation {
  country: string;
  region: string;
  city: string;
}

export async function getUserLocation(): Promise<GeoLocation> {
  // Normally, fetch from an IP geolocation service
  // For tests, this will be mocked
  const response = await fetch('https://api.ipgeolocation.io/ipgeo');
  return response.json();
}

Inject Mock Data During Testing

Use dependency injection or environment checks to replace real implementation with mocks.

// geoMock.ts
export const mockGeoLocations: Record<string, GeoLocation> = {
  'us': { country: 'US', region: 'California', city: 'San Francisco' },
  'de': { country: 'DE', region: 'Berlin', city: 'Berlin' },
  'jp': { country: 'JP', region: 'Tokyo', city: 'Tokyo' }
};

export async function getUserLocationMock(regionCode: string): Promise<GeoLocation> {
  return mockGeoLocations[regionCode] || mockGeoLocations['us'];
}

Configure Tests with Abstraction

During testing, selectively load mock implementations.

// main.ts
import { getUserLocation } from './geo'; // real
// import { getUserLocationMock } from './geoMock'; // mock

const isTestEnv = process.env.NODE_ENV === 'test';
const getLocation = isTestEnv ? getUserLocationMock : getUserLocation;

async function checkFeatureAccess() {
  const location = await getLocation('de'); // 'de' region for testing
  if (location.country === 'DE') {
    // execute geo-restricted feature
  }
}

Automate Geolocation Switches in CI

Using environment variables, you can automate region-specific testing.

# CI script example
export TEST_REGION=jp
node -r dotenv/config dist/index.js

And in your app:

const regionCode = process.env.TEST_REGION || 'us';
const location = await getUserLocationMock(regionCode);

Conclusion

By integrating TypeScript with open source libraries for mocking IP-based geolocation, we can create flexible, automated tests for geo-restricted features. This approach significantly enhances testing coverage, reduces manual intervention, and ensures that features dependent on physical location work correctly across different regions.

Implementing such strategies ensures reliability in widespread deployment scenarios and maintains a seamless user experience worldwide.