hyb-oa/server/tests/unit/scripts/feature-flag-apply-uncertainty.test.js

const {
  FEATURE_FLAG_APPLY_DECISION,
  executeFeatureFlagApplyAttempt,
} = require("../../../../scripts/qa/feature-flag-apply-uncertainty.mjs");

const TARGETS = Object.freeze([
  { flagKey: "announcements_v1", preVersion: 49, preOverrideMode: "force_on", postOverrideMode: "force_off" },
  { flagKey: "todo_board_v1", preVersion: 49, preOverrideMode: "force_on", postOverrideMode: "force_off" },
  { flagKey: "weekly_report_v1", preVersion: 49, preOverrideMode: "force_on", postOverrideMode: "force_off" },
]);

function state(kind) {
  return TARGETS.map((target, index) => {
    if (kind === "partial" && index === TARGETS.length - 1) {
      return { flagKey: target.flagKey, version: target.preVersion, overrideMode: target.preOverrideMode };
    }
    if (kind === "pre") {
      return { flagKey: target.flagKey, version: target.preVersion, overrideMode: target.preOverrideMode };
    }
    return { flagKey: target.flagKey, version: target.preVersion + 1, overrideMode: target.postOverrideMode };
  });
}

describe("feature flag apply uncertainty", () => {
  it("continues POST when APIRequestContext succeeds although the page observer sees zero", async () => {
    const sendBatch = vi.fn().mockResolvedValue({ count: 3 });
    const readCurrent = vi.fn().mockResolvedValue(state("post"));
    const rollback = vi.fn();

    const result = await executeFeatureFlagApplyAttempt({
      targets: TARGETS,
      payload: { items: TARGETS },
      sendMutation: sendBatch,
      readCurrent,
      observedRequestCount: 0,
    });

    expect(result).toMatchObject({
      decision: FEATURE_FLAG_APPLY_DECISION.CONTINUE_POST,
      classification: "APPLIED",
      sendAttemptCount: 1,
      responseKnown: true,
      response: { count: 3 },
      observedRequestCount: 0,
      observerMismatch: true,
    });
    expect(sendBatch).toHaveBeenCalledTimes(1);
    expect(readCurrent).toHaveBeenCalledTimes(1);
    expect(rollback).not.toHaveBeenCalled();
  });

  it("continues POST when the response is missing but readback proves POST state", async () => {
    const rollback = vi.fn();
    const result = await executeFeatureFlagApplyAttempt({
      targets: TARGETS,
      payload: { items: TARGETS },
      sendMutation: vi.fn().mockRejectedValue(new Error("transport_result_missing")),
      readCurrent: vi.fn().mockResolvedValue(state("post")),
    });

    expect(result).toMatchObject({
      decision: FEATURE_FLAG_APPLY_DECISION.CONTINUE_POST,
      classification: "APPLIED",
      sendAttemptCount: 1,
      responseKnown: false,
    });
    expect(rollback).not.toHaveBeenCalled();
  });

  it("stops without retry or rollback when the response is missing and readback remains PRE", async () => {
    const retry = vi.fn();
    const rollback = vi.fn();
    const result = await executeFeatureFlagApplyAttempt({
      targets: TARGETS,
      payload: { items: TARGETS },
      sendMutation: vi.fn().mockRejectedValue(new Error("transport_result_missing")),
      readCurrent: vi.fn().mockResolvedValue(state("pre")),
    });

    expect(result).toMatchObject({
      decision: FEATURE_FLAG_APPLY_DECISION.STOP_NOT_APPLIED,
      classification: "NOT_APPLIED",
      sendAttemptCount: 1,
      responseKnown: false,
    });
    expect(retry).not.toHaveBeenCalled();
    expect(rollback).not.toHaveBeenCalled();
  });

  it("stops unknown with zero mutation when readback fails", async () => {
    const retry = vi.fn();
    const rollback = vi.fn();
    const result = await executeFeatureFlagApplyAttempt({
      targets: TARGETS,
      payload: { items: TARGETS },
      sendMutation: vi.fn().mockRejectedValue(new Error("transport_result_missing")),
      readCurrent: vi.fn().mockRejectedValue(new Error("readback_unavailable")),
    });

    expect(result).toMatchObject({ decision: FEATURE_FLAG_APPLY_DECISION.STOP_UNKNOWN, classification: "READBACK_FAILED" });
    expect(retry).not.toHaveBeenCalled();
    expect(rollback).not.toHaveBeenCalled();
  });

  it("stops for manual decision with zero mutation when readback is partial", async () => {
    const continuePost = vi.fn();
    const rollback = vi.fn();
    const result = await executeFeatureFlagApplyAttempt({
      targets: TARGETS,
      payload: { items: TARGETS },
      sendMutation: vi.fn().mockRejectedValue(new Error("transport_result_missing")),
      readCurrent: vi.fn().mockResolvedValue(state("partial")),
    });

    expect(result).toMatchObject({
      decision: FEATURE_FLAG_APPLY_DECISION.STOP_FOR_MANUAL_DECISION,
      classification: "PARTIAL_OR_UNEXPECTED",
    });
    expect(result.observations.map((item) => item.state)).toEqual(["POST", "POST", "PRE"]);
    expect(continuePost).not.toHaveBeenCalled();
    expect(rollback).not.toHaveBeenCalled();
  });
});