Radamsa

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Introduction

Radamsa is a test case generator for robustness testing, a fuzzer. Its README says it is typically used to test how well a program withstands malformed and potentially malicious inputs, by reading sample files of valid data and generating interestingly different outputs.

Selling points are that it has found many bugs in programs that matter, is easily scriptable, and is easy to get running. It is black-box: no instrumentation, just a command that writes mutated inputs to files, stdout or a network socket, so any program in any language can be tested.

The project is hosted on GitLab under the MIT licence, with commits as recent as February 2026.

Saving every crashing input with its seed makes failures reproducible and easy to turn into regression tests.

Features

1. Sample-based mutation: Starts from valid files.
2. Black-box: No instrumentation needed.
3. Scriptable: Simple CLI.
4. Many outputs: Files, stdout or TCP.
5. Seeds: Reproducible runs.
6. Any target: Language-agnostic.

Pros

1. Free to use: Open source under MIT.
2. Simplicity: One command to start.

Cons

1. No coverage guidance: Less efficient than coverage-guided fuzzers.
2. Harness DIY: You script the loop.
3. Small community: Fewer updates.

Usage and Links (Example)

echo "HAL 9000" | radamsa
radamsa -n 100 -o fuzz-%n.json samples/*.json
for f in fuzz-*.json; do ./parser "$f" || echo "crash: $f"; done

Resources:

• Radamsa website

Pricing

Radamsa is free and open source under the MIT licence.

Recommended for?

1. Testers fuzzing black-box programs quickly.

Conclusion

Radamsa is the quickest way to throw malformed data at anything.

Pair it with coverage-guided fuzzing for depth.

On CheckOps, Radamsa is filed under the Security testing stage. Related tools listed here include libFuzzer, AFL++, honggfuzz, LibAFL, OSS-Fuzz and ClusterFuzzLite. A short trial on a real project, with your own code, data and pipeline, is usually the fastest way to choose between them, because fit matters more than feature lists. Facts here come from the official site, documentation and repository, checked on 11 November 2026.