Eris review
A focused PHP library for generating, shrinking, and replaying PHPUnit test cases.
Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
Eris is an open-source property-based testing library for PHP projects that use PHPUnit. It generates inputs from configurable domains, evaluates properties across repeated cases, and shrinks failing inputs toward simpler counterexamples. The library is aimed at teams that want property-based coverage within an existing PHPUnit workflow, with installation handled through Composer. It can also operate outside PHPUnit through its facade, although PHPUnit is its primary test-runner integration.
Its feature set centers on test generation and failure diagnosis. Scalar, collection, composite, and domain generators let teams describe different input spaces, while configurable iteration and time limits provide control over how much work a run performs. The published default is 100 generated values per forAll() call. Seeded test reproducibility and configurable pseudorandom-number generators support repeatable failures, and test-run listeners and logging add visibility around execution. Together, these capabilities make Eris a practical fit for teams that need more varied inputs than example-based tests typically provide without leaving PHP's established testing tools.
Eris is most appropriate for PHPUnit-based PHP teams seeking a focused, self-hosted library rather than a hosted testing platform. Its narrow scope can be an advantage when the priority is generators, shrinking, replay, and PHPUnit compatibility. Teams working in another language, using a different test runner, or looking for a broader stateful-testing focus should consider an alternative. There is no paid tier to evaluate: Eris is distributed as open-source software, with Composer and PHPUnit forming the central ecosystem around it. Choose Eris for property-based testing embedded in PHP test suites; look elsewhere when cross-language coverage or broader testing modes are central requirements.
Eris pros and cons
- Where it wins
- Generators cover scalar, collection, composite, and domain-specific inputs
- Shrinking and seeded replay simplify failure diagnosis and reproduction
- Configurable limits, listeners, logging, and PHPUnit integration support test workflows
- Where it doesn't
- PHP support limits it to PHP-based projects
- Self-hosted Composer library rather than a hosted testing service
- Stateful testing sits outside its stated focus
Eris fact sheet, pricing and score →
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