> ## Documentation Index
> Fetch the complete documentation index at: https://docs.zapier.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Compute a field from the data of the Test API call

> Zapier doesn't store the responses from the test API call for OAuth v2 and session authentication. Using computed fields, you can use data from a test API call later in your Zapier integration.

## Prerequisites

* Knowledge of working with APIs
* Understanding of computed field concept
* Familiarity with JavaScript

## Steps

1. Log into the [Platform UI](https://zapier.com/app/developer).
2. Select your **integration**.
3. In the *Build* section in the left sidebar, click your **authentication**.
   * For Session authentication:
     * Click **Configure a Token Exchange Request**
     * Click **Switch to Code Mode**.
   * For OAuth v2 authentication:
     * Click **Add OAuth v2 Endpoint Configuration**.
     * Click **Switch to Code Mode**.
4. Add **custom JavaScript code** to instruct Zapier to call both the URLs necessary for the authorization process and your test API call.
5. Click **Save & Continue**.
6. The *Test Request* section remains unchanged.
7. Return [computed fields](https://github.com/zapier/zapier-platform/blob/main/packages/cli/README.md#computed-fields) for data returned from either API call so you can reference those fields in subsequent steps as `bundle.authData.field` where `field` is the field's name from your test API call response.

Upon completion, you will be able to use data from a test API call as a computed field in later stages of your Zapier integration.

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