Mock Data Processing Workflow with Error Handling

Overview

This workflow demonstrates a simple data processing pipeline using n8n's built-in Function nodes. It starts with a manual trigger, generates mock data, transforms it, and includes a dedicated error handler to catch and stop the workflow on failure. It's an excellent starting point for learning how to manipulate data in n8n and implement basic error management.

Node-by-Node Breakdown

1. Manual Trigger (No auth) — Provides a button in the n8n editor to manually start the workflow. No scheduling or webhook is used; you click "Execute Workflow" to run it.
2. Mock Data (n8n Function Node, No auth) — This node uses custom JavaScript code to generate an array of four mock items: "item-1", "item-2", "item-3", "item-4". It wraps each item in the standard n8n .json format for downstream processing.
3. Function (n8n Function Node, No auth) — Takes the array from the previous node and maps each item into a new object with a data key. For example, "item-1" becomes { data: "item-1" }. This is a common transformation pattern to reshape data before output or storage.
4. Error Handler (Stop and Error Node, No auth) — Connected as an error workflow (although not wired in connections here), this node stops execution and throws a custom error message ("Workflow execution error"). In practice, it would be triggered if any previous node fails, preventing partial or corrupt data from propagating.

Setup Instructions

1. No external accounts required — This workflow runs entirely within n8n and uses only built-in nodes. You do not need any API keys, OAuth, or external services.
2. Import the JSON into your n8n instance via Workflows > Add Workflow > Import from File.
3. Click Execute Workflow on the Manual Trigger node to see the mock data flow through the Function nodes.
4. To test error handling, intentionally break the code in the Mock Data node (e.g., return invalid syntax) and observe how the Error Handler stops execution.

Use Cases & Variations

• Learning & Prototyping: Perfect for beginners to understand data flow, JSON transformation, and error handling in n8n without external dependencies.
• Data Transformation Pattern: Replace the Mock Data node with an HTTP Request or database query to fetch real data, then use the Function node to clean or restructure it.
• Error Handling Template: Use the Stop and Error node as a pattern for any production workflow where you need to halt processing on failure and log a meaningful message.
• CI/CD Pipelines: Combine with webhook triggers to simulate data processing within automated testing environments.

To adapt: Change the functionCode in Mock Data to pull from an API or CSV, or modify the Function node to aggregate, filter, or enrich the data.

{
  "nodes": [
    {
      "id": "trigger-a3a1cb65",
      "name": "Manual Trigger",
      "type": "n8n-nodes-base.manualTrigger",
      "typeVersion": 1,
      "position": [
        100,
        100
      ],
      "parameters": {}
    },
    {
      "name": "Mock Data",
      "type": "n8n-nodes-base.function",
      "position": [
        550,
        300
      ],
      "parameters": {
        "functionCode": "return [{json:[\"item-1\", \"item-2\", \"item-3\", \"item-4\"]}];"
      },
      "typeVersion": 1,
      "id": "acde4709-5dca-4894-80aa-c041f4a858e5",
      "notes": "This function node performs automated tasks as part of the workflow."
    },
    {
      "name": "Function",
      "type": "n8n-nodes-base.function",
      "position": [
        750,
        300
      ],
      "parameters": {
        "functionCode": "return items[0].json.map(item => {\n  return {\n    json: {\n      data:item\n    },\n  }\n});\n"
      },
      "typeVersion": 1,
      "id": "7cd01085-4de7-479d-99c1-974df410f456",
      "notes": "This function node performs automated tasks as part of the workflow."
    },
    {
      "id": "error-bf6f52d3",
      "name": "Error Handler",
      "type": "n8n-nodes-base.stopAndError",
      "typeVersion": 1,
      "position": [
        1000,
        400
      ],
// ... truncated (copy to see full JSON)