# opendiffy/diffy

Repository: https://github.com/opendiffy/diffy
Canonical: https://ross.abutalabs.com/products/opendiffy-diffy
Language: Java
License: NOASSERTION
License Family: other
Last push: 2026-05-18T08:50:36+00:00

## Health v2 (maintenance only)
Score: 60/100 (v2, computed 2026-09-02T17:46:02.011165+00:00)
- activity 83, release rhythm 8, longevity 100
- inputs: {"age_days": 3051, "days_push": 107, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: no_license
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1461, forks 164 (observed 2026-08-28T04:04:47.553258+00:00)

## What it is
Diffy is a differential testing tool that sends identical requests to a candidate service and a reference (primary/secondary) service, then diffs the responses to surface regressions without writing tests. It is a Java-based service used in production at companies like Twitter, Airbnb, and Mixpanel.

## Use cases
- safely rewrite a high-throughput service and verify behavior parity
- run shadow testing when migrating between API gateways
- catch regressions in a new service version before deploying it
- compare candidate and reference service responses automatically
- test microservices without writing test cases

## When to choose
- you are rewriting or migrating a service and need automated behavioral comparison
- you want the shadow/differential testing pattern used by Twitter and Airbnb
- you have both a stable reference service and a candidate service to compare

## When to avoid
- you need a general-purpose unit or integration test framework
- you have no reference implementation to diff against
- your license requires permissive open-source terms (license is CC BY-NC-ND)

## Facets
- artifact type: service
- maturity: active
- function: testing, e2e-testing, http-client, developer-tools
- domain: testing, developer-tools, apis, microservices
- platform: jvm, cross-platform, cli
- tags: differential-testing, shadow-testing, regression-testing, api-testing, traffic-mirroring, docker

## Member repositories
- opendiffy/diffy (main) score 60

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:04:47.553258+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T04:35:21.586729+00:00, confidence not recorded.
  - readme: https://github.com/opendiffy/diffy (fetched 2026-08-28T04:04:47.553258+00:00, sha 70c3a7ffe21c)
- Data as of 2026-08-30T08:39:29.467469+00:00.