Rapid
- Android app
- Not listed
- Free plan
- Yes
- Runs on
- self-hosted
Summary
Rapid is a Go library for property-based testing: it checks user-defined properties against test cases generated automatically. Its type-safe, generic generators favor small values and edge cases. When a failure occurs, Rapid reduces the failing case before presenting it, and it can save minimized failures and rerun them. It also supports state machine testing, and its MakeFuzz function lets a Rapid test serve as a target for Go’s standard fuzzer. Tests run with `go test`; options can be configured with `-rapid.` flags or matching `RAPID_` environment variables. Rapid has no dependencies beyond the Go standard library and is licensed under the Mozilla Public License Version 2.0. The project says tests should continue to work across future releases within the same major version, subject to API-change exceptions. Rapid describes itself as suited to structured data and state machine tests compared with Go’s `testing.F.Fuzz`, but it does not provide coverage-guided feedback or mutations. The library is free, with a listed plan price of 0.00 USD per free.
Who it is for
Rapid suits Go developers who want generated test cases for checking properties, especially for structured data or state machine tests. It may be less suited to those who need coverage-guided feedback or mutations.
What is good
- Minimizes failing test cases automatically.
- Can persist and rerun minimized failures.
- Supports state machine testing.
- Has no dependencies beyond Go’s standard library.
- Tests run with `go test`.
What to know first
- Does not provide coverage-guided feedback.
- Does not provide mutations.
Verdict
Rapid offers property-based testing, failure minimization, and state machine support in a Go library with no external dependencies. Its stated limitation is the lack of coverage-guided feedback and mutations.
Rapid plans and pricing
All plansCompared on property-based testing tools
- Free plan
- Yespgregory.net
- Supported languages
- Gopgregory.net
- Test runner support
- Go testing package; go testpgregory.net
- Failing-case shrinking
- Yespgregory.net
- Stateful testing
- Yespgregory.net
- Reproducible failures
- Yespgregory.net
Facts
- What it does
- Rapid is a Go library for property-based testing that checks user-defined properties against automatically generated test cases.github.com · 3 Oct 2026
- Automatic minimization
- When a failure is found, Rapid automatically minimizes the failing test case before presenting it.github.com · 3 Oct 2026
- Data generation
- Its type-safe generators use generics and bias data generation toward small values and edge cases.github.com · 3 Oct 2026
- Failure persistence
- Rapid supports persisting minimized failing test cases and automatically rerunning them.github.com · 3 Oct 2026
- Dependencies
- Rapid has no dependencies outside the Go standard library.github.com · 3 Oct 2026
- Fuzzing integration
- The MakeFuzz function lets a Rapid test be used as a fuzz target for Go's standard fuzzer.github.com · 3 Oct 2026
- Usage
- Rapid tests run with the standard go test command.github.com · 3 Oct 2026
- Configuration
- Rapid's options can be set with flags prefixed -rapid. or corresponding RAPID_ environment variables.github.com · 3 Oct 2026
- Stability
- The project says tests should continue to work across future releases with the same major version, subject to stated API-change exceptions.github.com · 3 Oct 2026
- License
- Rapid is licensed under the Mozilla Public License Version 2.0.github.com · 3 Oct 2026
- Comparison limit
- Compared with Go's testing.F.Fuzz, Rapid describes itself as better suited to structured data and state machine tests, while lacking coverage-guided feedback and mutations.github.com · 3 Oct 2026
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Sources
- github.com/flyingmutant/rapid· checked 3 Oct 2026