Fiber app.Test request-context compatibility boundary across major versions

Answer first

Do not assert listener-derived request context values in handler-level app.Test tests. Reserve assertions on c.IP(), c.Secure(), c.Protocol() and c.Hostname() for a separate local-listener smoke test. Define a stable contract across Fiber major versions by isolating listener-populated fields behind an explicit adapter and testing business logic with injected fakes via c.Locals in app.Test.

There is no documented compatibility boundary in model knowledge that formally separates safe app.Test coverage from listener-dependent behavior. The boundary must be defined by the team per the major version pinned in go.mod.

Confirmed facts

• app.Test exercises the Fiber app stack in-process without binding a network listener. Tests can run without production credentials by injecting fakes through c.Locals.
• Fiber’s test helper, default configuration and Ctx accessor semantics are tied to the major version resolved in go.mod.

Likely explanation, version-sensitive

• Remote address, TLS state, protocol and hostname are normally populated by the fasthttp server layer when app.Listen is used.
• Under in-process app.Test those fields may be empty or default. The exact defaults are version-sensitive and can change between Fiber major releases, so a handler branching on those values can pass under app.Test in one release and behave differently under app.Listen or another release.

Stable contract steps for this case

1. Pin the Fiber major version and treat it as part of the test contract. Verify with grep fiber go.mod or go list -m all | grep fiber.
2. Isolate listener-dependent values behind an adapter. Handlers should read IP, Secure, Protocol, Hostname through a small wrapper that first checks injected c.Locals and falls back to c.IP() etc.
3. Test business logic with app.Test using injected Locals only. Do not assert on raw c.IP() etc in these tests.
4. Add a minimal local-listener smoke test on localhost that starts app.Listen and asserts the adapter mapping for listener-populated context values. No production credentials required.
5. Review release notes for the pinned major version for changes to app.Test, RequestCtx initialization and Ctx accessors after any major upgrade.

Assumption: you are using Fiber v2 or v3 style app.Test(req, -1) API. If the major version is different, Ctx method defaults and app.Test initialization can differ, which changes the recommendation.

One missing diagnostic detail that changes the recommendation: which Fiber major version is pinned in go.mod right now. Provide that version so the exact defaults for c.IP(), c.Secure(), c.Protocol(), c.Hostname() under app.Test can be verified.