n8n-expression-testing

The n8n-expression-testing skill is a specialized engineering agent designed to ensure the robustness and security of complex n8n workflow expressions. It provides a structured approach to validating JavaScript-based expressions within n8n nodes, preventing common runtime failures caused by malformed syntax, null pointer dereferences, or insecure coding practices. This tool is essential for workflow developers, automation engineers, and QA specialists who manage large-scale data pipelines and require high reliability for their data transformation logic. By automating the review process, it significantly reduces the debugging time typically required when dealing with dynamic $json, $node, and $items references.

• Syntax validation: Analyzes expression strings for valid JavaScript structure, effectively stripping template markers to check for errors before deployment.

• Context variable verification: Ensures that critical context variables like $json, $node, $items, $now, and $workflow are correctly referenced and typed.

• Security analysis: Detects the usage of dangerous functions such as eval() or Function() constructors to mitigate potential injection risks.

• Automated test generation: Simulates execution with provided context data to catch boundary errors, type coercion issues, and missing fallback values.

• Performance optimization: Identifies inefficient array operations or recursive logic that could lead to performance bottlenecks in workflows handling large data sets.

• Input/Output: Accepts raw expression strings and target context data; outputs structured validation reports, error diagnostic messages, and corrected code snippets.

• Best practices: Implements null-safe access patterns using optional chaining (?.) and coalescing operators (??) to prevent undefined property access.

• Compatibility: Supports the full spectrum of n8n built-in methods, including Date manipulation via Luxon, string formatting, and complex object manipulation.

• Constraints: Primarily designed for standard n8n expression environments; assumes Node.js-compatible JavaScript execution contexts.