Merge Wait vs Append Topology Divergence Harness

How it works

1. 1.Manual Trigger fires with one empty item
2. 2.Generate Dataset builds fictional records and stamps scenario and expectedBranches on each item
3. 3.Branch A Items and Branch B Items normalize fields and carry scenario; empty branch B emits an __emptyBranch marker
4. 4.Branch B Is Empty? routes the marker to NoOp and real records to Merge
5. 5.Append Merge (append, 3 inputs) collects the append-path output
6. 6.Simulated Wait Gate forwards records only if all expected branches arrived, else emits one blocked item
7. 7.Merge Both Topologies joins both path outputs
8. 8.Compare Topologies returns a single divergence report item
9. 9.Divergence Summary adds harness version, schema note and action hint

Use cases

• Verify Merge behaviour before an n8n version upgrade
• Prove which topology yields full output when a branch is empty
• Test multi-branch record normalization and invalid amount detection
• Document merge behaviour when migrating workflows between environments

Requirements

• n8n supporting the listed node typeVersions
• No credentials and no network access
• Replace Generate Dataset with your real source using schema {recordId, branch, label, amount}
• Expected branch list comes from the expectedBranches field

Setup and testing in n8n

1. Import the JSON and open the workflow
2. Click Execute Workflow and inspect the single Divergence Summary item
3. Confirm scenario=deliberate_empty_branch_B, appendRecordCount=2, simulatedWaitRecordCount=0 and divergent=true
4. Add a branch B record in Generate Dataset and re-run: the gate should pass and counts should match
5. Use a string amount to confirm amountValid=false

Service Value

Ready-made workflow template for automation delivery and service execution.