Deterministic flags in CI and unit tests

A test that reads a flag over the network is flaky by construction: it depends on what the dashboard says right now, it fails in CI behind a firewall, and a teammate flipping a gate breaks an unrelated build. You want flag-gated code to be testable the way the rest of your code is — deterministic, offline, and explicit about what each case sets.

The SDK gives you two levels: configureForTesting() + overrides for unit tests, and configureForOffline() with a captured snapshot for integration and CI. Both replace the active configuration, so a suite can reconfigure freely between cases — and your code under test keeps reading through the ordinary new Client(user).

Unit tests — configureForTesting() + overrides

configureForTesting() swaps in a no-network configuration that's already "ready": nothing fetches, track() is a no-op, assign() logs no exposure, telemetry is off, and no SDK key is required. You seed each case explicitly:

import { configureForTesting, Client, clearOverrides } from "@shipeasy/sdk/server";

configureForTesting({
  flags: { new_checkout: true },
  configs: { upload_limits: { max_uploads: 50 } },
});

const flags = new Client({ user_id: "u1" });
flags.getFlag("new_checkout"); // true
flags.getConfig("upload_limits"); // { max_uploads: 50 }
flags.track("purchase"); // no-op — never hits the network

clearOverrides(); // reset between cases

The browser is identical via configureForTesting() from @shipeasy/sdk/client.

Integration / CI — a captured snapshot

When you want the real rule set — actual targeting, actual bucketing, real universes — without a live dependency, evaluate against a snapshot. A snapshot is just the two SDK wire bodies:

import { configureForOffline, Client } from "@shipeasy/sdk/server";

// from a JSON file on disk (Node only)
configureForOffline({ path: "./snapshot.json" });

// …or from an object you already hold (works anywhere)
// `snapshot` carries both SDK wire bodies — the second one is required even
// when your tests only read flags and configs.
configureForOffline({ snapshot: { flags, experiments } });

const flags = new Client({ user_id: "u1" });
flags.getFlag("new_checkout"); // real eval, no network
flags.getConfig("upload_limits"); // real eval, no network

Rollout & measurement plan