Open-source platform combining product analytics, session replay, A/B testing, and feature flags in one toolkit for product engineers.
Supercov
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About Supercov
Supercov integrates with coding agents to measure and improve test coverage. It runs via the command line using npx supercov, which analyzes the latest uncovered gaps in the codebase. The tool then provides the agent with the next most useful test to write, focusing on uncovered paths rather than random additions. Each iteration reruns the test suite, updates coverage metrics, and continues until no further useful gaps remain. Supported test suites include Jest, Vitest, Playwright, Cargo, pytest, RSpec, Mocha, AVA, and others. The process is designed to work overnight or during idle agent time, converting unused tokens into measurable coverage improvements. Coverage metrics tracked include line, branch, and MC/DC percentages, with instrumentation designed for low overhead to maintain fast test loops.
Key features
- Measures line, branch, and MC/DC coverage
- Identifies next useful test to write
- Integrates with Jest, Vitest, Playwright, Cargo, pytest, RSpec, Mocha, AVA
- Command-line tool via npx supercov
- Tracks coverage improvements over iterations
- Supports overnight or idle agent time usage
- Provides JSON output for automation
- Open-source and extensible
Use cases
- Improving test coverage for JavaScript/TypeScript projects overnight
- Guiding coding agents to write focused tests during idle time
- Incrementally increasing coverage in software factories using agents
Pros
- Command-line integration via npx
- Supports multiple test frameworks
- Tracks line, branch, and MC/DC coverage
- Low-overhead instrumentation
- Open-source and MIT licensed
Cons
- Limited to JavaScript, TypeScript, Rust, Python, and Ruby
- Requires coding agents for operation
- No explicit support for Java, C#, or other languages yet
Frequently asked questions about Supercov
What is Supercov and how does it work?
Supercov is a tool that integrates with coding agents to measure and improve test coverage. It runs via the command line using `npx supercov`, analyzes uncovered gaps in the codebase, and provides the agent with the next most useful test to write. The process continues until no further useful gaps remain.
Which coding agents does Supercov support?
Supercov supports coding agents such as Claude Code, Codex, Cursor, Gemini CLI, GitHub Copilot, and others. It can be used with any coding agent that operates within a repository.
What test suites are compatible with Supercov?
Supercov supports multiple test suites, including Jest, Vitest, Playwright, Cargo, pytest, RSpec, Mocha, AVA, and others. It is designed to work with a variety of testing frameworks across different languages.
How does Supercov improve test coverage?
Supercov focuses on uncovered paths rather than random additions, guiding agents to write tests that specifically target gaps in coverage. Each iteration reruns the test suite, updates coverage metrics, and continues until no further useful gaps remain.
What coverage metrics does Supercov track?
Supercov tracks line, branch, and MC/DC coverage percentages. The instrumentation is designed to have low overhead, ensuring fast test loops while maintaining accurate metrics.
Is Supercov free to use?
Yes, Supercov is free and open source, licensed under the MIT license. Users can inspect, extend, and run it anywhere.
