fast-check vs PropEr

fast-check9.4Visit PPropEr8.7Visit

Higher score fast-check #1 in Property-Based Testing Tools 9.4/10 Open source Free plan✓ 3 of 3 features Visit fast-check

vs

P PropEr #7 in Property-Based Testing Tools 8.7/10 Free plan Free plan✓ 2 of 3 features Visit PropEr

• fast-check fits best

  JavaScript and TypeScript teams

• PropEr fits best

  Erlang teams testing stateful systems

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Side by side

Feature	fast-check 9.4/10 Visit ↗	PPropEr 8.7/10 Visit ↗
At a glance
Editor score	9.4	8.7
Ranking	#1 in Property-Based Testing Tools	#7 in Property-Based Testing Tools
Best for	JavaScript and TypeScript teams	Erlang teams testing stateful systems
Pricing model	Free	Free
Starting price	Open source	Free plan
Free plan	✓	✓
Free trial	—	—
Deployment	Self-hosted	Self-hosted
Support	Docs, Community	Community
Integrations	7 integrations	2 integrations
Built for	Solo, Small business, Mid-market, Enterprise	Solo, Small business, Mid-market, Enterprise
Features fast-check 3/3 · PropEr 2/3
Failing-case shrinking	✓	✓
Stateful testing	✓	✓
Reproducible failures	✓ (best)	Not checked yet
Specs
Supported languages	JavaScript, TypeScript	Erlang
Test runner support	Jest, Mocha, Vitest, Ava, Bun, Deno, Node.js test runner	EUnit, Common Test
Cases per run	Not checked yet	Not checked yet
Our review
Pros	Shrinks failures and supports deterministic replay with seeds and paths Supports stateful, asynchronous, fuzzing, and scheduler-based testing Integrates with Jest, Mocha, Vitest, Ava, Bun, Deno, and Node.js	Generates inputs from PropEr types and native Erlang types Tests stateful systems with generated command sequences Attempts to shrink failures and supports targeted testing
Cons	Its scope is limited to JavaScript and TypeScript Advanced stateful and scheduler workflows require thoughtful test design It does not provide AI-assisted testing features	Supports Erlang rather than a range of programming languages Requires a self-hosted deployment Support is community-based
Our verdict	fast-check is an open-source property-based testing library for JavaScript and TypeScript. It generates inputs, runs properties repeatedly, and reduces failing inputs to smaller cases that are easier to investigate. The library suits teams… Read the review →	PropEr is an open-source property-based testing tool for developers writing Erlang programs. Rather than checking only hand-picked examples, teams define properties and input types, then generate inputs to check whether those properties… Read the review →

Strengths and trade-offs

• fast-check — where it wins

  • Shrinks failures and supports deterministic replay with seeds and paths
  • Supports stateful, asynchronous, fuzzing, and scheduler-based testing
  • Integrates with Jest, Mocha, Vitest, Ava, Bun, Deno, and Node.js

  Where it doesn't

  • Its scope is limited to JavaScript and TypeScript
  • Advanced stateful and scheduler workflows require thoughtful test design
  • It does not provide AI-assisted testing features

• PropEr — where it wins

  • Generates inputs from PropEr types and native Erlang types
  • Tests stateful systems with generated command sequences
  • Attempts to shrink failures and supports targeted testing

  Where it doesn't

  • Supports Erlang rather than a range of programming languages
  • Requires a self-hosted deployment
  • Support is community-based

• fast-check9.4/10 · Open source

  A deep, runner-agnostic testing library for JavaScript and TypeScript teams.

  Visit fast-checkFull verdict →
• PPropEr8.7/10 · Free plan

  A focused Erlang tool for generated properties, stateful models, and smaller failure cases.

  Visit PropErFull verdict →