Mutode

Paid

What Mutode is

Mutode is a free, open-source mutation testing tool for JavaScript and Node.js projects. It introduces small code changes, called mutants, then runs the project’s tests to see whether they detect them: a failing test kills a mutant, while a passing test means it survived. The tool reports killed, survived and discarded mutants and calculates mutant coverage, including reports for surviving mutants. Its documented operators can change boolean, numeric and string literals, alter conditionals and operators, or remove array elements, function arguments, object properties, lines and switch cases. Users can select mutation operators and configure concurrent runners; the documented default is four. For parallel runs, Mutode creates project copies for its runners and saves logs in a `.mutode` folder. It first runs the project’s `npm test` command and reports an error rather than proceeding if the clean test suite exits with a nonzero code. Mutode requires Node 8 or later and is licensed under MIT. The documentation describes global or local npm installation, npx use and package.json scripts.

Who it suits

Mutode suits JavaScript and Node.js developers who want to check whether their test suites catch small code changes. It is relevant to projects that run tests through npm and can use Node 8 or later.

What it does well

Free and open source under MIT.
Reports killed, survived and discarded mutants.
Users can choose mutation operators.
Concurrency defaults to four runners.
Supports global, local and npx execution.

What to know first

Requires Node 8 or later.
Runs the project’s npm test command first.
Documentation does not list third-party integrations.

Limits

Mutode requires Node 8 or later, and its run begins with the project’s npm test command. The documented default concurrency is 4, although the runner count can be configured.

Getting started

Open the Mutode project website
Install Mutode globally with npm or as a local development dependency
Use npx or add a package.json script to run it
Ensure the project’s npm test command completes successfully
Select mutation operators with the mutators option if needed
Set concurrency for the mutant runners if needed

Verdict

Mutode adds mutation testing to JavaScript and Node.js projects, with configurable operators and runner concurrency. Its clean-test prerequisite and Node version requirement are important to check before using it.

Questions

What does Mutode test?

It performs mutation testing for JavaScript and Node.js projects by changing code and running the project’s tests.

Is Mutode free?

Yes. Mutode is free and open source, and the project uses the MIT license.

How can Mutode be installed?

The documentation describes global npm installation, local development-dependency installation, npx use, and package.json scripts.

What happens before mutation testing?

Mutode runs the project’s npm test command and reports an error if that clean test suite exits with a nonzero code.

Can concurrent runners be configured?

Yes. Users can set the number of runners; the documented default concurrency is 4, and project copies are created for parallel execution.

Facts from Mutode's own pages

Concurrency: The concurrency option controls mutant runners and defaults to 4. · thesoftwaredesignlab.github.io, 9 Oct 2026
Configuration: Users can select mutation operators and set concurrency; the command-line documentation gives a default concurrency of 4. · thesoftwaredesignlab.github.io, 4 Oct 2026
How it works: It makes small code changes called mutants and runs the test suite; failing tests kill a mutant, while passing tests mean it survived. · thesoftwaredesignlab.github.io, 9 Oct 2026
Install: The page documents global npm installation, local development dependency installation, npx usage, and package.json scripts. · thesoftwaredesignlab.github.io, 4 Oct 2026
Installation: The page documents installing Mutode globally with npm or locally as a development dependency. · thesoftwaredesignlab.github.io, 9 Oct 2026
Integrations: The documentation describes npm installation and execution but does not list third-party service integrations. · thesoftwaredesignlab.github.io, 4 Oct 2026
Intended users: Mutode is a mutation testing tool for JavaScript and Node.js projects. · thesoftwaredesignlab.github.io, 4 Oct 2026
License: The page identifies the license as MIT and names Diego Rodríguez Baquero in its copyright notice. · thesoftwaredesignlab.github.io, 9 Oct 2026
Logs: Mutode saves logs in a .mutode folder in the project. · thesoftwaredesignlab.github.io, 4 Oct 2026
Mutation operators: Documented operators include changing literals and conditionals, altering math operators, and removing code elements such as array elements, function arguments, lines, and switch cases. · thesoftwaredesignlab.github.io, 9 Oct 2026
Operator selection: Users can select mutation operators with the --mutators option. · thesoftwaredesignlab.github.io, 9 Oct 2026
Parallel execution: Mutode creates project copies for concurrent mutant runners and supports configuring the number of runners. · thesoftwaredesignlab.github.io, 4 Oct 2026
Purpose: Mutode performs mutation testing for Node.js and JavaScript. · thesoftwaredesignlab.github.io, 9 Oct 2026
Results: Mutode reports killed, survived, and discarded mutants and calculates mutant coverage. · thesoftwaredesignlab.github.io, 4 Oct 2026
Runtime requirement: Mutode requires Node 8 or later. · thesoftwaredesignlab.github.io, 9 Oct 2026
Security and compliance: The opened product pages do not state security certifications or compliance claims. · thesoftwaredesignlab.github.io, 4 Oct 2026
Test requirement: Mutode runs the project’s npm test command before proceeding and reports an error if the clean test suite exits with a nonzero code. · thesoftwaredesignlab.github.io, 4 Oct 2026
Ways to run: The page documents running Mutode directly, with npx, or through a package.json script. · thesoftwaredesignlab.github.io, 9 Oct 2026
What it does: Mutode generates small code changes called mutants and runs tests to reveal whether the tests detect them. · thesoftwaredesignlab.github.io, 4 Oct 2026

Where Mutode stands on Freedom251

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