Localization Testing with Karate: A Geo-Aware API Strategy

APIs can seem simple. A request. A response. A status code. Then you realize those responses change depending on where the request comes from.

A travel app’s pricing endpoint might return euros in France and dollars in the United States. A financial platform might include different legal disclaimers based on local regulations. An e-commerce API could show region-specific offers or restrict access entirely.

These differences are not bugs. They are essential for compliance and localization. Testing them is the challenge. Mocking headers is not enough, and switching VPNs to reflect locations does not scale.

This is where Karate and WonderProxy work together. One handles automation. The other provides location awareness.

Why geo-aware API testing matters

Localization testing isn’t just about language. For APIs, it means verifying that business logic behaves correctly in every region you serve.

APIs often change responses based on where a request originates, not just what parameters it sends. Pricing, legal text, and feature availability can vary by location.

Typical differences include:

• Currencies and formats: USD vs. CAD, or MM/DD/YYYY vs. DD/MM/YYYY.
• Regulatory content: GDPR disclaimers in Europe, FDIC language in the United States.
• Localized offers: Promotions visible only in specific markets.
• Access control: Data or features restricted by licensing rules.

These variations usually rely on server-side IP detection, so header overrides alone won’t expose them.

A simple endpoint like /api/v1/offer can return very different payloads depending on where the request originates:

{
  "country": "CA",
  "offer": "10% off grooming in Toronto",
  "disclaimer": "Offer valid only in Ontario."
}

To validate this logic, your tests must do two things:

1. Route traffic through different geographic locations.
2. Automatically verify that each localized response matches expectations.

That’s where Karate and WonderProxy pair naturally. One handles assertion logic, the other handles geographic context.

Karate: Lightweight API testing that speaks your language

Karate is an open-source API testing framework designed for clarity and automation. It combines Behavior-Driven Development (BDD)-style readability with strong JSON and XML assertions.

For localization testing, Karate excels because it lets you express expectations in clear, human-readable syntax. You don’t need to write full Java test classes or complex fixtures.

Example of a simple Karate test using BDD-style syntax to create and validate an API resource.

Here’s a simple example that checks if an API returns the right offer per region:

Feature: Verify localized offers

Scenario Outline: Validate offers per region
  Given url 'https://api.example.com/offers'
  And header X-Region = '<region>'
  When method get
  Then status 200
  And match response.country == '<region>'
  And match response.offer contains '<expectedOffer>'

Examples:
  | region | expectedOffer              |
  | US     | "off grooming in New York" |
  | CA     | "off grooming in Toronto"  |

This approach works well for APIs that rely on headers, but many production systems use IP-based routing. That’s where Karate alone reaches its limit, and where WonderProxy steps in.

WonderProxy: Making APIs think you’re somewhere else

WonderProxy provides global proxy servers that route your traffic through real locations around the world. Each request appears to originate from a specific city or country, triggering the same logic that real users experience.

For developers, this means you can:

• Test region-restricted APIs without leaving your desk.
• Validate that compliance text, pricing, or content changes as expected.
• Integrate location-based checks into automated test pipelines.

WonderProxy handles the routing, so your tests don’t need complex network configurations. Simply connect through a proxy, and your requests automatically adopt that region’s IP address.

Running Karate tests through WonderProxy

You’ve seen how Karate handles assertions and how WonderProxy provides location routing. Now let’s put them together.

The following example shows how to run a simple Karate test suite through WonderProxy to simulate requests from multiple regions.

Step 1: Get your WonderProxy credentials

After setting up a WonderProxy account, you’ll have access to a list of servers (e.g., Toronto, London, Tokyo). Each server comes with a hostname and port number, like:

proxy.wonderproxy.com:11000

You’ll also have a username and password to authenticate your proxy connection.

Step 2: Configure Karate’s proxy settings

Karate lets you define global configurations in karate-config.js. Here’s how you tell Karate to route all traffic through WonderProxy:

function fn() {
  var config = {};
  karate.configure('proxy', 'http://USERNAME:PASSWORD@proxy.wonderproxy.com:11000');
  return config;
}

You can change servers at any time by adjusting the port number to match your target location.

Step 3: Switch locations dynamically

Karate supports environment profiles, which makes it easy to test across multiple WonderProxy locations.

Command line example:

karate.env=tokyo mvn test

Inside karate-config.js, map each environment to a specific proxy:

if (karate.env == 'tokyo') {
  karate.configure('proxy', 'http://user:pass@proxy.wonderproxy.com:11001');
}

Now your tests will appear to come from Tokyo, triggering the Japanese version of your API.

Step 4: Assert geo-specific responses

Once the proxy routing is in place, your Karate assertions can validate content differences as if you were in those regions:

Then match response.disclaimer contains "MiFID II"

Run the same test through a U.S. proxy, and you might expect:

Then match response.disclaimer contains "FDIC insured"

Combining proxy routing with data-driven assertions lets you verify multiple localized behaviors in a single automated run.

Example: Testing legal disclaimers in a finance API

Suppose you manage a global investment API that adapts its legal text by region. U.S. users might see “FDIC insured up to $250,000”, while EU users receive “Compliant with MiFID II regulations,” and Canadian users see “Accounts insured by CDIC.”

With Karate and WonderProxy, you can verify all of these in one test file.

Feature: Verify legal disclaimers per region

Scenario Outline: Regional disclaimers
  Given url 'https://api.finapp.com/legal'
  When method get
  Then status 200
  And match response.disclaimer contains '<expectedText>'

Examples:
  | proxyPort | expectedText   |
  | 11000     | "FDIC insured" |
  | 11002     | "MiFID II"     |
  | 11005     | "CDIC"         |

Run the suite across the different WonderProxy servers listed in the table.
Each test routes through a new location and validates that the returned disclaimer text matches local compliance rules.

This approach confirms that your localization logic works everywhere without switching VPNs or maintaining multiple environments.

Why WonderProxy + Karate is the perfect match

Karate and WonderProxy each solve different parts of the same problem. The table below shows how their strengths combine to create a complete geo-aware testing workflow.

Together, they create a lightweight yet powerful framework for testing how your API behaves in every country you serve.

Best practices for geo-aware API tests

Geo-aware testing is most effective when your setup stays consistent and repeatable. These practices help teams maintain reliable results as they expand coverage across multiple regions.

1. Centralize your test data
Keep regional expectations (like currency, disclaimer text, or offer strings) in a single JSON or CSV. That way, your test logic stays clean while your assertions remain flexible.

2. Use tags for different locales
Karate supports tagging tests (@us, @ca, @eu) so you can run only relevant subsets during regression or smoke testing.

3. Cache static responses
If your endpoints have rate limits or long TTLs, cache them locally between runs. This reduces overhead and speeds up validation.

4. Test content, not just status codes
A 200 OK response doesn’t mean it’s the right regional content. Always check for the actual localized fields in the JSON.

4. Rotate locations regularly
WonderProxy’s global server list helps you test both major markets and edge regions. These include areas such as South America, Africa, and Southeast Asia, where localization issues are more likely to occur.

Following these practices keeps your localization tests consistent and scalable. They also help your team catch subtle regional issues before they reach production.

Scaling localization tests in CI/CD

Both Karate and WonderProxy integrate cleanly into a CI/CD workflow. You can automate geo-aware tests the same way you schedule other build or regression tasks.

Karate runs headless with Maven, Gradle, or npm scripts.
WonderProxy credentials can be stored securely as environment variables.
Together, they let you run nightly jobs that validate all key endpoints across global proxies.

Example Jenkins step:

for port in 11000 11002 11005
do
  karate.env=$port mvn test
done

Build confidence in localized APIs

APIs are global by nature, but their responses are often local by design. Testing that behavior manually is slow and incomplete.

Pairing Karate’s automation with WonderProxy’s global reach enables QA teams to verify that every region receives the right experience. Whether it’s a price shown in yen, a disclaimer written in French, or an offer available only in Toronto, the tests confirm that localization works as intended.

Geo-aware API testing isn’t just about correctness; it’s about trust. And when your tests can see the world like your users do, trust scales right alongside your product.