Supercov

Coverage for coding agents and software factories

Measure code coverage with npx supercov and write one test.

Star on GitHub

How Supercov works

Supercov gives coding agents the deepest JavaScript coverage for code verification, including MC/DC and assertion coverage.

Read more
CodexClaude CodeCursorGemini CLIGitHub Copilot
CodexClaude CodeCursorGemini CLIGitHub Copilot
Improve test coverage•••

Working

Supercov gives the agent the next test to write.

Each run returns the uncovered paths. The agent adds focused tests, reruns the suite, and continues while useful gaps remain.

Coverage agents can act on.

File-by-file coverage, uncovered paths, and assertion gaps—so your agent knows what to test next.

Assertion coverage

Recorded execution shows the total calculation ran in the passing test. The agent traces order.status to its assertion, but finds no assertion for order.total. For two items at $25, it adds expect(order.total).toBe(50). A wrong total now fails this test. Finding the gap does not require executing mutated code.

Read more

Find missing assertions without mutation testing.

Your agent traces what tests check using recorded execution evidence. No mutants to generate or execute.

Supported bySupercorp

3.4kGitHub stars↗

npm downloads

200k+weekly downloads

Supported by Supercorp.

Backed by Supercorp’s open-source track record.

  • RSpec
  • Minitest
  • Jest
  • Mocha
  • Vitest
  • Vitest Browser Mode
  • pytest
  • Playwright
  • node:test
  • AVA
  • cargo test
  • cargo-nextest
  • unittest
  • Cucumber
  • test-unit
  • rustdoc
  • go test
  • JUnit 5
  • TestNG
  • Kotest
  • Spock

Supported test suites.

Playwright, Vitest, Jest, Cargo, pytest, RSpec, go test, JUnit, and more.

Use leftover tokens on coverage.

Before a reset—or overnight—turn idle agent time into coverage that stays with the repository.

For software factories.

Every pass returns fresh, executable evidence, so agents can keep iterating around the clock while regressions are caught before they ship.

Low overhead.

Fast instrumentation keeps the test loop moving.

Any language.

JavaScript, TypeScript, Rust, Python, Ruby, Go, Java, and Kotlin—with more to come.

Any agent.

Claude Code, Codex, Cursor, Gemini CLI, GitHub Copilot—and more.

How Supercov compares.

JavaScript & TypeScript

Coverage features for JavaScript & TypeScript
FeatureSupercovVitestnyc / Istanbulc8
Line coverageSupportedSupportedSupportedSupported
Branch coverageSupportedSupportedSupportedSupported
MC/DCSupportedNot built inNot built inNot built in
Per-test coverageSupportedNot built inNot built inNot built in
Assertion coverageSupportedNot built inNot built inNot built in
Sources and notes September 14, 2026
  • Vitest uses its standard V8 or Istanbul coverage provider here. Supercov works with your existing test runner.
  • Per-test coverage means individual tests, not test files. Supercov needs a supported runner; concurrency can limit attribution.
  • Assertion coverage links source to passing assertions through an agent-reviewed map. It is not a mutation score or proof of correctness.

Python

Coverage features for Python
FeatureSupercovcoverage.pySlipCover
Line coverageSupportedSupportedSupported
Branch coverageSupportedSupportedSupported
MC/DCSupportedNot built inNot built in
Per-test coverageSupportedSupportedNot built in
Assertion coverageSupportedNot built inNot built in
Sources and notes September 14, 2026
  • Supercov requires CPython 3.12+ for full coverage. pytest-cov uses coverage.py; enable test contexts for per-test coverage.
  • Per-test coverage means individual tests, not test files. Supercov needs a supported runner; concurrency can limit attribution.
  • Assertion coverage links source to passing assertions through an agent-reviewed map. It is not a mutation score or proof of correctness.

Ruby

Coverage features for Ruby
FeatureSupercovSimpleCov
Line coverageSupportedSupported
Branch coverageSupportedSupported
MC/DCSupportedNot built in
Per-test coverageSupportedSupported
Assertion coverageSupportedNot built in
Sources and notes September 14, 2026
  • Supercov supports MRI Ruby: full MC/DC on 3.4+, limited measurement on 3.3. SimpleCov 1.3 requires Ruby 3.3+.
  • SimpleCov’s per-test coverage requires track_tests. Neither tool promises exact per-test coverage for overlapping threaded tests.
  • Per-test coverage means individual tests, not test files. Supercov needs a supported runner; concurrency can limit attribution.
  • Assertion coverage links source to passing assertions through an agent-reviewed map. It is not a mutation score or proof of correctness.

Rust

Coverage features for Rust
FeatureSupercovcargo-llvm-covTarpaulin
Line coverageSupportedSupportedSupported
Branch coverageSupportedSupportedNot built in
MC/DCSupportedSupportedNot built in
Per-test coverageSupportedNot built inNot built in
Assertion coverageSupportedNot built inNot built in
Sources and notes September 14, 2026
  • Supercov requires Rust 1.95 and supported Cargo runners. cargo-llvm-cov’s branch and MC/DC flags require nightly. Tarpaulin’s branch option is not implemented.
  • Per-test coverage means individual tests, not test files. Supercov needs a supported runner; concurrency can limit attribution.
  • Assertion coverage links source to passing assertions through an agent-reviewed map. It is not a mutation score or proof of correctness.

Built-in coverage reports, unless noted. Read the comparisons