Skip to main content

A/B Test Outbound

Custom Policy Example

Zuplo is extensible, so we don't have a built-in policy for A/B Test Outbound, instead we have a template here that shows you how you can use your superpower (code) to achieve your goals. To learn more about custom policies see the documentation.

This example shows how to perform an action on incoming requests based on the result of a randomly generated number. A/B tests could also be performed on properties such as the request.user.

A/B tests can also be combined with other policies by passing data to downstream policies. For example, you could save a value in ContextData based on the results of the A/B test and use that value in a later policy to modify the request.

Example Custom Policy

The code below is an example of how this custom policy module could be implemented.

import { ZuploContext, ZuploRequest } from "@zuplo/runtime";

export default async function (
response: Response,
request: ZuploRequest,
context: ZuploContext,
) {
// Generate a random number to segment the test groups
const score = Math.random();

// Get the outgoing response body
const data = await response.json();

// Modify the body based on the random value
if (score < 0.5) {
data.testEnabled = true;
} else {
data.testEnabled = false;

// Stringify the data object
const body = JSON.stringify(data);

// Return a new response with the updated body
return new Response(body, response);


The example below shows how to configure a custom code policy in the 'policies.json' document that utilizes the above example policy code.

"name": "ab-test-outbound",
"policyType": "custom-code-outbound",
"handler": {
"export": "default",
"module": "$import(./modules/ab-test-outbound)"
  • name the name of your policy instance. This is used as a reference in your routes.
  • policyType the identifier of the policy. This is used by the Zuplo UI. Value should be ab-test-outbound.
  • handler/export The name of the exported type. Value should be default.
  • handler/module the module containing the policy. Value should be $import(./modules/YOUR_MODULE).

Read more about how policies work