Template validation
The CLI checks IDs, channels, optional subjects, bodies and flat sample data before any delivery step exists.
Day 059 / n8n / Workflow Automation
Notification Template Lab
/ Overview
A dependency-free Python CLI that validates placeholders, flags missing or unused variables, and previews complete notification templates locally.
Notification text often moves from a document into an automation with placeholders that are easy to miss, mistype or leave unused. Testing by sending a real message adds avoidable risk, while error logs can expose sample values.
/ Provided servicesClear thinking.
Clear thinking.
Practical delivery.
Safe preview gate
A preview appears only when every referenced variable has a supplied value; blocked reports list variable names without their values.
Defensive input
Duplicate JSON keys, unknown fields, nested values, duplicate IDs and bounded-size violations fail with a clear validation error.
/ Solution
Notification Template Lab reads one bounded local JSON plan, extracts explicit double-brace placeholders, checks them against flat string or number data, and renders only complete templates. It reports missing and unused variable names, rejects duplicate keys, duplicate IDs, unknown fields and oversized input, and returns distinct exit codes for ready, blocked and invalid plans. It does not send messages, connect to n8n, fetch secrets or certify a production workflow.
/ Impact
Stable placeholder extraction
Blocked partial previews
Unused-variable checks
Value-free diagnostics
Three meaningful exit states
Python standard library
Argparse, dataclasses, JSON, regular expressions and unittest keep the build dependency-free.
Text and JSON output
Human-readable and machine-readable reports support local review and later workflow integration.
Eleven tests
Tests cover rendering, token order, missing and unused data, duplicate keys and IDs, invalid fields and exit behavior.