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test-perf-leaks

CPU-profile and leak-detect existing vitest suites via env-gated instrumentation.

518|49|Updated Apr 7, 2021
Search Tags:#memory leak#Vitest#Performance Testing#moon#Node#heap snapshot#CPU profiling
One-click install
npx skills add https://github.com/dxos/dxos --skill test-perf-leaks
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: test-perf-leaks
Source: https://github.com/dxos/dxos/tree/main/.agents/skills/test-perf-leaks
Command: npx skills add https://github.com/dxos/dxos --skill test-perf-leaks

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve?

Node test suites that run slowly or grow memory across a run are hard to diagnose without modifying test code. This Skill instruments the shared vitest node project through opt-in environment variables, producing V8 CPU profiles and heap snapshots from an existing suite with zero edits to the test file.

Core Features & Use Cases

  • CPU Profiling: Set DX_PROFILE_TESTS to emit a V8 .cpuprofile via Node --cpu-prof, viewable in Chrome DevTools or speedscope to find hotspots.
  • Leak Detection: Set DX_DEBUG_LEAKS to inject a setup file that captures before/after heap snapshots plus a per-test heapUsed slope in heap-samples.ndjson.
  • Use Case: A suite in the echo or sdk package keeps growing in memory across tests. Run it with DX_DEBUG_LEAKS=1, read the heap slope for a monotonic rise, then diff the before/after snapshots in DevTools Comparison view to find the retainer chain holding the leaked objects.

Quick Start

Run DX_DEBUG_LEAKS=1 moon run <pkg>:test --force -- src/foo.test.ts to leak-check a single vitest suite and inspect the generated heap snapshots.

Frequently Asked Questions about test-perf-leaks

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I CPU profile a vitest test suite?▼

Set DX_PROFILE_TESTS=1 and run moon run <pkg>:test --force -- src/foo.test.ts. This emits a V8 .cpuprofile into the package's profiles directory, which you can open in Chrome DevTools Performance panel or speedscope to inspect self time.

How to detect memory leaks in node tests?▼

Set DX_DEBUG_LEAKS=1 and run the suite with moon run <pkg>:test --force -- src/foo.test.ts. It writes before/after heap snapshots and a per-test heapUsed slope in heap-samples.ndjson; a monotonic rise across tests indicates a real leak.

Does this work with browser or workerd test suites?▼

No, the instrumentation is wired only into the node vitest project created by createNodeProject. Browser, storybook, and workerd suites are not supported, and profiling the running Composer app requires separate app-side heap tooling.

Why must I pass --force when running the profiled test?▼

The env vars are declared as moon task inputs, so a repeat run with identical inputs would hydrate the cached result and skip vitest entirely, producing no fresh profile. The --force flag re-executes the task unconditionally.

Why should I target only one test file for leak detection?▼

The leak model assumes a single suite in one process, giving one clean before/after snapshot pair. Multiple files would create ambiguity about which file ran last and mix heap samples across suites.

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