Module 3 Lesson 5: Testing & Debugging

Building a workflow is only 50% of the job. The other 50% is fixing it when it breaks. "Debug" is the most common button you will press in n8n.

1. The "Step Through" Method

Don't run the whole workflow at once.

1. Select a node.
2. Click "Execute Node."
3. Inspect the Output on the right.

• Is the email spelled correctly?
• Is the number a string or an integer?

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2. Reading the JSON (The Source of Truth)

Every node has a Toggle at the top: Table view vs JSON view.

• Table view is pretty.
• JSON view is Accurate. Always check the JSON if an expression isn't working. You might find hidden nested fields or "Null" values that the table view hid from you.

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Visualizing the Process

graph TD
    Start[Input] --> Process[Processing]
    Process --> Decision{Check}
    Decision -->|Success| End[Complete]
    Decision -->|Retry| Process

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3. The "Pin Data" Feature

If you are testing an "Email Sent" node, you don't want to actually send 50 emails to your boss while you are debugging.

• Click the "Pin" icon on the input data.
• Now, the node will "Freeze" that data. You can re-run the node 100 times, and it will use the pinned data instead of asking the previous (possibly expensive or slow) node for new info.

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4. Execution Logs (Looking at the Past)

Found in the Sidebar.

• You can filter by "Failed" executions.
• You can click an old execution and see EXACTLY what data was present at every single node at that moment in time.

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Exercise: The Debugging Detective

1. Create a workflow that intentionally fails (e.g., an HTTP Request to a fake URL like https://aksjdhfkajsdh.com).
2. Execute the workflow.
3. Open the red node. What is the Error Message?
4. Pin some "Mock" data to a SET node.
5. Why is "Pinning" essential when you are working with a trigger like "New Stripe Payment"?
6. Research: How do you "Disable" a node so the workflow skips over it during a test?

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Summary

You have completed Module 3: The n8n Workflow. You now know how to start a workflow, transform data with action nodes, write custom code, direct the flow with logic, and debug when things go wrong.

Next Module: The language of data: Module 4: Working with Data (JSON, Strings, Math).