feat: support jest.resetModules for CJS modules

__test__/jest/jest.resetModules.test.cjs

@@ -0,0 +1,24 @@
+test('jest.resetModels', () => {
+  const a = require('c8')
+  a.foo = 'bar'
+  expect(a.foo).toBe('bar')
+
+  const b = require('c8')
+  expect(a).toBe(b)
+  expect(b.foo).toBe('bar')
+
+  jest.resetModules()
+
+  const c = require('c8')
+  expect(c).not.toBe(a)
+  expect(c).not.toBe(b)
+  expect(c.foo).toBe(undefined)
+
+  expect(a).toBe(b)
+  expect(b.foo).toBe('bar')
+
+  const d = require('c8')
+  expect(d).not.toBe(a)
+  expect(d).not.toBe(b)
+  expect(d).toBe(c)
+})

src/jest.js

@@ -2,7 +2,7 @@ import assert from 'node:assert/strict'
 import { describe as nodeDescribe, test as nodeTest, afterEach } from 'node:test'
 import { format, types } from 'node:util'
 import { jestfn, allMocks } from './jest.fn.js'
-import { jestmock, requireActual, requireMock } from './jest.mock.js'
+import { jestmock, requireActual, requireMock, resetModules } from './jest.mock.js'
 import * as jestTimers from './jest.timers.js'
 import './jest.snapshot.js'
 import { expect } from 'expect'
@@ -67,6 +67,7 @@ const jest = {
   mock: jestmock,
   requireMock,
   requireActual,
+  resetModules,
   ...jestTimers,
 }
 

src/jest.mock.js

@@ -25,6 +25,11 @@ export function requireMock(name) {
   return mapMocks.get(resolved)
 }
 
+export function resetModules() {
+  // Caveat: only resets CJS modules, not ESM
+  for (const key of Object.keys(require.cache)) delete require.cache[key]
+}
+
 const isObject = (obj) => [Object.prototype, null].includes(Object.getPrototypeOf(obj))
 
 function override(resolved, lax = false) {