jest-mock 29.7.0: ModuleMocker

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify jest-mock.ModuleMocker in pkg:npm/jest-mock@29.7.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/jest-mock@29.7.0
Demonstrate these symbols/APIs:
  - jest-mock.ModuleMocker

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:d457b5a2a48222883b7c8684303de0343e2061adfc9d906201b8dffe6a234fb0","contract":["ModuleMocker constructor initializes an instance bound to an environment global","ModuleMocker fn creates callable mock functions verified by isMockFunction","ModuleMocker getMetadata extracts structured metadata schema for objects and functions","ModuleMocker generateFromMetadata creates mock objects preserving members with mock implementations","ModuleMocker spyOn wraps target methods to intercept invocations and track calls","ModuleMocker replaceProperty replaces object properties and tracks them for restoration","ModuleMocker clearAllMocks, resetAllMocks, and restoreAllMocks manage mock lifecycle and states"],"goal":"verify jest-mock.ModuleMocker in pkg:npm/jest-mock@29.7.0","kind":"HOW","packages":["pkg:npm/jest-mock@29.7.0"],"schemaVersion":1,"symbols":["jest-mock.ModuleMocker"]},"contractCommand":["node","test/contract.mjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","executionContext":"node","language":"javascript","libc":"glibc","libcVersion":"2.39","moduleSystem":"esm","os":"linux","osVersionBucket":"24","packageManager":"npm","packageManagerVersion":"10.9.8","runtime":"node","runtimeVersion":"22.23.2","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/jest-mock@29.7.0"],"schemaVersion":1,"subject":"pkg:npm/jest-mock@29.7.0","symbols":["jest-mock.ModuleMocker"],"verifierAdapter":"node-typescript@1"}

{
  "name": "sample-jest-mock-module-mocker",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-jest-mock-module-mocker",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "jest-mock": "29.7.0"
      }
    },
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}

{
  "name": "sample-jest-mock-module-mocker",
  "version": "1.0.0",
  "private": true,
  "type": "module",
  "license": "MIT-0",
  "dependencies": {
    "jest-mock": "29.7.0"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify jest-mock.ModuleMocker in pkg:npm/jest-mock@29.7.0",
  "kind": "HOW",
  "packages": [
    "pkg:npm/jest-mock@29.7.0"
  ],
  "symbols": [
    "jest-mock.ModuleMocker"
  ]
}

import { ModuleMocker } from "jest-mock";

/**
 * Creates and initializes a ModuleMocker instance bound to the given environment global.
 *
 * @param {typeof globalThis} [globalObject=globalThis] - Global object used to create mocks.
 * @returns {ModuleMocker} Initialized ModuleMocker instance.
 */
export function createModuleMocker(globalObject = globalThis) {
  return new ModuleMocker(globalObject);
}

/**
 * Creates a mock function using the provided ModuleMocker instance.
 *
 * @param {ModuleMocker} mocker - ModuleMocker instance.
 * @param {Function} [implementation] - Optional implementation for the mock function.
 * @returns {import("jest-mock").Mock} Created mock function.
 */
export function createMockFunction(mocker, implementation) {
  return mocker.fn(implementation);
}

/**
 * Checks whether a given function or value is a mock function created by ModuleMocker.
 *
 * @param {ModuleMocker} mocker - ModuleMocker instance.
 * @param {unknown} candidate - Value to check.
 * @returns {boolean} True if the candidate is a mock function, false otherwise.
 */
export function isFunctionMock(mocker, candidate) {
  return mocker.isMockFunction(candidate);
}

/**
 * Extracts structural mock metadata schema for a component (object, function, or class).
 *
 * @param {ModuleMocker} mocker - ModuleMocker instance.
 * @param {unknown} component - Component to inspect.
 * @returns {object|null} Metadata descriptor for the component.
 */
export function extractMetadata(mocker, component) {
  return mocker.getMetadata(component);
}

/**
 * Generates a mock object structure from a metadata descriptor.
 *
 * @param {ModuleMocker} mocker - ModuleMocker instance.
 * @param {object} metadata - Metadata descriptor schema.
 * @returns {object} Mocked object with mock function members.
 */
export function generateMockObject(mocker, metadata) {
  return mocker.generateFromMetadata(metadata);
}

/**
 * Spies on an object method using the ModuleMocker instance.
 *
 * @param {ModuleMocker} mocker - ModuleMocker instance.
 * @param {object} target - Target object containing the method.
 * @param {string} methodName - Name of the method to spy on.
 * @returns {import("jest-mock").MockInstance} Spied mock instance.
 */
export function spyOnTargetMethod(mocker, target, methodName) {
  return mocker.spyOn(target, methodName);
}

/**
 * Replaces an object property with a new value using the ModuleMocker instance.
 *
 * @param {ModuleMocker} mocker - ModuleMocker instance.
 * @param {object} target - Target object.
 * @param {string} propertyKey - Name of the property.
 * @param {unknown} value - New property value.
 * @returns {import("jest-mock").Replaced} Replaced property handle.
 */
export function replaceTargetProperty(mocker, target, propertyKey, value) {
  return mocker.replaceProperty(target, propertyKey, value);
}

/**
 * Clears recorded invocation history across all mock functions in the mocker.
 *
 * @param {ModuleMocker} mocker - ModuleMocker instance.
 */
export function clearMockerCalls(mocker) {
  mocker.clearAllMocks();
}

/**
 * Resets recorded calls and custom implementations across all mock functions in the mocker.
 *
 * @param {ModuleMocker} mocker - ModuleMocker instance.
 */
export function resetMockerImplementations(mocker) {
  mocker.resetAllMocks();
}

/**
 * Restores original implementations for all spies and replaced properties in the mocker.
 *
 * @param {ModuleMocker} mocker - ModuleMocker instance.
 */
export function restoreMockerSpies(mocker) {
  mocker.restoreAllMocks();
}

export { ModuleMocker };

import assert from "node:assert/strict";
import { ModuleMocker } from "jest-mock";
import {
  createModuleMocker,
  createMockFunction,
  isFunctionMock,
  extractMetadata,
  generateMockObject,
  spyOnTargetMethod,
  replaceTargetProperty,
  clearMockerCalls,
  resetMockerImplementations,
  restoreMockerSpies
} from "../src/index.mjs";

// 1. ModuleMocker constructor initializes an instance bound to an environment global
{
  assert.equal(typeof ModuleMocker, "function");
  const mocker = createModuleMocker(globalThis);
  assert.ok(mocker instanceof ModuleMocker);
}

// 2. ModuleMocker fn creates callable mock functions verified by isMockFunction
{
  const mocker = createModuleMocker();
  const mockFn = createMockFunction(mocker, (x) => x * 10);
  assert.equal(isFunctionMock(mocker, mockFn), true);
  assert.equal(isFunctionMock(mocker, () => {}), false);
  assert.equal(isFunctionMock(mocker, null), false);

  const result = mockFn(7);
  assert.equal(result, 70);
  assert.deepEqual(mockFn.mock.calls, [[7]]);
  assert.equal(mockFn.mock.results[0].type, "return");
  assert.equal(mockFn.mock.results[0].value, 70);
}

// 3. ModuleMocker getMetadata extracts structured metadata schema for objects and functions
{
  const mocker = createModuleMocker();
  const target = {
    compute: (a, b) => a + b,
    fixedVal: 100,
    nested: {
      action: () => "done"
    }
  };
  const metadata = extractMetadata(mocker, target);
  assert.equal(metadata.type, "object");
  assert.equal(metadata.members.compute.type, "function");
  assert.equal(metadata.members.compute.name, "compute");
  assert.equal(metadata.members.fixedVal.type, "constant");
  assert.equal(metadata.members.fixedVal.value, 100);
  assert.equal(metadata.members.nested.type, "object");
  assert.equal(metadata.members.nested.members.action.type, "function");
}

// 4. ModuleMocker generateFromMetadata creates mock objects preserving members with mock implementations
{
  const mocker = createModuleMocker();
  const service = {
    banner: "welcome",
    format: (msg) => `[${msg}]`
  };
  const metadata = extractMetadata(mocker, service);
  const mockedService = generateMockObject(mocker, metadata);

  assert.equal(mockedService.banner, "welcome");
  assert.equal(isFunctionMock(mocker, mockedService.format), true);

  mockedService.format.mockReturnValue("mocked-output");
  assert.equal(mockedService.format("test"), "mocked-output");
  assert.deepEqual(mockedService.format.mock.calls, [["test"]]);
}

// 5. ModuleMocker spyOn wraps target methods to intercept invocations and track calls
{
  const mocker = createModuleMocker();
  const calculator = {
    multiply(a, b) {
      return a * b;
    }
  };
  const spy = spyOnTargetMethod(mocker, calculator, "multiply");
  assert.equal(isFunctionMock(mocker, spy), true);
  assert.equal(calculator.multiply(3, 4), 12);
  assert.deepEqual(spy.mock.calls, [[3, 4]]);

  spy.mockImplementation((a, b) => a + b);
  assert.equal(calculator.multiply(3, 4), 7);

  restoreMockerSpies(mocker);
  assert.equal(calculator.multiply(3, 4), 12);
}

// 6. ModuleMocker replaceProperty replaces object properties and tracks them for restoration
{
  const mocker = createModuleMocker();
  const settings = { port: 3000, host: "localhost" };
  const handle = replaceTargetProperty(mocker, settings, "port", 8080);
  assert.equal(settings.port, 8080);

  handle.replaceValue(9090);
  assert.equal(settings.port, 9090);

  handle.restore();
  assert.equal(settings.port, 3000);
}

// 7. ModuleMocker clearAllMocks, resetAllMocks, and restoreAllMocks manage mock lifecycle and states
{
  const mocker = createModuleMocker();
  const fn1 = createMockFunction(mocker, () => "alpha");
  const fn2 = createMockFunction(mocker, () => "beta");
  const target = {
    getValue() {
      return "original";
    }
  };
  const spy = spyOnTargetMethod(mocker, target, "getValue");
  spy.mockReturnValue("spied");

  fn1();
  fn2();
  assert.equal(target.getValue(), "spied");
  assert.equal(fn1.mock.calls.length, 1);
  assert.equal(fn2.mock.calls.length, 1);
  assert.equal(spy.mock.calls.length, 1);

  clearMockerCalls(mocker);
  assert.equal(fn1.mock.calls.length, 0);
  assert.equal(fn2.mock.calls.length, 0);
  assert.equal(spy.mock.calls.length, 0);

  resetMockerImplementations(mocker);
  assert.equal(fn1(), undefined);

  restoreMockerSpies(mocker);
  assert.equal(target.getValue(), "original");
}

console.log("All jest-mock.ModuleMocker contract assertions passed.");