---
title: "Test API for On API Call Starter"
slug: "transactional-journeys-test-api-for-on-api-call-starter"
updated: 2026-01-27T10:52:41Z
published: 2026-01-27T10:52:41Z
canonical: "academy.insiderone.com/transactional-journeys-test-api-for-on-api-call-starter"
---

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

# Test API for On API Call Starter

> **Suggested readings**: [Test Transactional Journeys](/v1/docs/test-transactional-journeys), [Preview and Test Message](/v1/docs/transactional-journeys-preview-and-test-message)

Test API allows you to validate your request payload before activating a transactional journey. It helps identify structural issues early and ensures the payload will be accepted when sent to the live endpoint.

Test API performs the limitation checks without enqueuing users into the journey.

To access the Test API, simply navigate to [**On API Call Starter**](/v1/docs/transactional-journeys-on-api-call-starter) > **Test API**.

This guide explains the following?

- [How does Test API work?](/v1/docs/test-api-for-on-api-call-starter#how-does-test-api-work)
- [Successful payloads](/v1/docs/test-api-for-on-api-call-starter#successful-payloads)
- [Unsuccessful payloads](/v1/docs/test-api-for-on-api-call-starter#unsuccessful-payloads)

## How does Test API work?

Once you create a payload in the On API Call starter, you can test it using the Test API.

After execution:

- The **HTTP status** indicates whether the payload passed validation.
- The **Response Body** explains the result.
- No users enter into the journey.

If the response is **not** **successful**, the **error** **message** explains which rule was violated.

![](https://cdn.document360.io/c6df4583-da94-4cb2-bb8a-be0cbdd11109/Images/Documentation/Bildschirmfoto 2025-12-29 um 18.40.49.png)

## Successful payloads

Below is a sample successful payload.

```json
{
        "idempotency_key": "string",
        "targets": [
        {
        "type": "journey_id",
        "value": 1001
        }
        ],
        "users": [
        {
        "identifier": {
        "type": "email",
        "value": "string"
        },
        "dynamic_attributes": {
        "user": {
        "name": "Sarah"
        }
        }
        }
        ]
        }
```

### Status Response: HTTP 200 OK

The **payload** includes all **required** fields and follows the **schema** rules.

The Response Body confirms that the payload is **valid** and can be used safely when the journey is **active**. No further action is required.

## Unsuccessful payloads

### HTTP 400 - Code 1000: Empty JSON Body

The Test API requires a **JSON** **body**. Your payload contains an **empty object** that lacks the required fields.

Below is a sample unsuccessful payload.

```json
{}
```

![](https://cdn.document360.io/c6df4583-da94-4cb2-bb8a-be0cbdd11109/Images/Documentation/Bildschirmfoto 2025-12-29 um 18.57.25.png)

#### How can you fix this error?

Add all required root-level fields:

- idempotency_key
- targets
- users

The request body must include a **valid** **structure**, even for testing.

### HTTP 400 - Code 1003: More Than 100 Users

A single API request can include **up to 100 users**. The Test API enforces the same limit.

Below is a sample payload.

```json
{
        "idempotency_key": "user-test-101",
        "targets": [
        { "type": "journey_id", "value": 1001 }
        ],
        "users": [
        { "identifier": { "type": "uuid", "value": "00000000-0000-0000-0000-000000000001" } }
        // ...
        ,
        { "identifier": { "type": "uuid", "value": "00000000-0000-0000-0000-0000000000101" } }
        ]
        }
    
```

![](https://cdn.document360.io/c6df4583-da94-4cb2-bb8a-be0cbdd11109/Images/Documentation/Bildschirmfoto 2025-12-29 um 18.58.08.png)

#### How can you fix this error?

Reduce the number of users to **100** or **fewer** in the users array. If you need to send more users, split them into **multiple** **requests**.

### HTTP 400 - Code 1003: Exactly One Target Required

The Test API requires exactly one target journey. This error occurs if the payload includes multiple targets or no targets.

#### Case 1: Multiple targets

Below is a sample payload.

```json
{
        "idempotency_key": "multi-target-test",
        "targets": [
        { "type": "journey_id", "value": 1001 },
        { "type": "journey_id", "value": 1002 }
        ],
        "users": [
        {
        "identifier": {
        "type": "iid",
        "value": "123456789"
        }
        }
        ]
        }
```

![](https://cdn.document360.io/c6df4583-da94-4cb2-bb8a-be0cbdd11109/Images/Documentation/Bildschirmfoto 2025-12-29 um 18.58.43.png)

#### How can you fix this error?

Keep only **one object** in the targets array. **Remove** all additional targets so the request points to a single journey.

#### Case 2: No targets

Below is a sample payload.

```json
{
        "idempotency_key": "no-target-test",
        "users": [
        {
        "identifier": {
        "type": "iid",
        "value": "123456789"
        }
        }
        ]
        }
```

![](https://cdn.document360.io/c6df4583-da94-4cb2-bb8a-be0cbdd11109/Images/Documentation/Bildschirmfoto 2025-12-29 um 18.59.20.png)

#### How can you fix this error?

Add a targets array with exactly one journey reference. The journey must be identified using type: journey_id.