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Infection

Free#4 of 25 in Mutation Testing Tools

Infection: A free, open-source PHP mutation testing framework with CI quality gates. Ranked #4 of 25 in Mutation Testing Tools by our editors (7.4/10); pricing: Free plan; best for PHP teams with CI quality gates.

7.4/10Editor score
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Infection7.4 Visit Infection

At a glance

  • Editor score
    7.4 / 10
  • Pricing
    Free plan
  • Best for
    PHP teams with CI quality gates
  • Free plan
    Yes
  • Paid from
    None
  • Mutation quality gate
    Yes
  • Facts checked
    20 Sep 2026
Infection screenshot

  • Where it wins

    • Broad PHP mutators with configurable profiles and custom mutators
    • Parallel execution, coverage reuse, and changed-line filtering
    • CI thresholds with HTML, text, JSON, GitHub, and GitLab reports

  • Where it doesn't

    • Supports PHP rather than multiple programming languages
    • No AI features are included
    • Mutation analysis is centered on supported PHP test frameworks

Our verdict on Infection

Infection is an open-source mutation testing framework for PHP teams that want to measure whether their tests detect code changes. It uses AST-based source-code mutation, runs relevant test cases, and reports killed, escaped, errored, and timed-out mutants. PHPUnit, PhpSpec, Codeception, and Testo are supported, making it a focused option for PHP projects with established automated test suites. The tool is free and distributed under the BSD-3-Clause license, with local installation available through PHAR, Composer, Phive, Git, or Homebrew.

Its strongest fit is continuous integration quality control. Teams can set mutation-score thresholds, reuse existing coverage reports, and filter analysis to changed lines or Git diffs. Parallel execution with configurable threads can support larger mutation runs, while HTML, text, JSON, GitHub, and GitLab reports provide different ways to review results or publish them in development workflows. Optional PHPStan and Mago integration adds static-analysis support alongside mutation testing. These capabilities give PHP teams several ways to control scope and connect results to existing quality gates.

Infection also offers a broad set of configurable mutators, including arithmetic, boolean, cast, conditional boundary, equality, function signature, nullify, number, operator, regex, removal, return value, visibility, and unwrap mutations. Custom mutators allow teams to tailor the analysis further. The trade-off is its narrow language focus: projects outside PHP need a different tool, and teams looking for AI features will not find them here. Infection is a strong choice for PHP teams that want open-source mutation analysis and measurable CI thresholds, but less suitable for polyglot organizations seeking one mutation-testing system across languages.

Infection pricing

Plans Free planFree Free to use — no paid tier required for the core job.
See plans on infection.github.io

Infection fact sheet

Free planYes
Paid fromNone
Supported languagesPHP
Test frameworksPHPUnit, PhpSpec, Codeception, Testo
Incremental analysisYes
Parallel executionYes
Surviving mutant reportsYes
Mutation quality gateYes
Mutation operatorsArithmetic, boolean, cast, conditional boundary, conditional negotiation, equality, function signature, nullify, number, operator, regex, removal, return value, visibility, and unwrap mutators
DeploymentSelf-hosted
SupportCommunity, Docs
Built forSolo, Small business, Mid-market, Enterprise (editorial estimate)
Integrations6 integrations: PHPUnit, PhpSpec, Codeception, Testo, PHPStan, Mago
PricingFree plan
Websiteinfection.github.io
Facts checked20 Sep 2026

Infection integrations

Infection lists 6 integrations on its own site.

  • PHPUnit
  • PhpSpec
  • Codeception
  • Testo
  • PHPStan
  • Mago

Alternatives to Infection

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Infection vs the competition

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Featured on iTechGuides

Featured on iTechGuides — Infection 7.4/10

Infection is listed in our Mutation Testing Tools directory. Add the badge to your site — it links back to this page.

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Reviewed by iTechGuides Editors · Editorial team · Updated Sep 2026

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