test: fix test that was not testing what it claimed

Author: ItsHarper

packages/parser/jest.config.js

@@ -2,6 +2,7 @@
 
 /** @type {import('@jest/types').Config.InitialOptions} */
 module.exports = {
+  setupFilesAfterEnv: ['jest-extended/all'],
   testEnvironment: 'node',
   testRegex: '/__tests__/(test|.*\\.test)\\.ts$',
   transform: {

packages/parser/package.json

@@ -29,6 +29,7 @@
     "@types/node": "^24.2.1",
     "is-ci-cli": "^2.2.0",
     "jest": "^29.7.0",
+    "jest-extended": "^6.0.0",
     "typescript": "^5.9.2"
   },
   "publishConfig": {

packages/parser/src/__tests__/test.ts

@@ -1,5 +1,7 @@
 import { parse, buildOptions } from '..'
+import { ParserPlugin } from '@babel/parser'
 import * as t from '@babel/types'
+import 'jest-extended'
 
 test('defaults `sourceType` to "unambiguous"', () => {
   expect(buildOptions().sourceType).toBe('unambiguous')
@@ -99,9 +101,18 @@ test('includes "decorators" plugin with options by default', () => {
 })
 
 test('does not include "decorators" plugin if "decorators-legacy" is already enabled', () => {
-  expect(buildOptions({ plugins: ['decorators-legacy'] })).not.toContain(
-    'decorators'
-  )
+  function isDecoratorsPlugin(plugin: ParserPlugin): boolean {
+    return (
+      plugin === 'decorators' ||
+      (Array.isArray(plugin) && plugin[0] === 'decorators')
+    )
+  }
+
+  expect(
+    buildOptions({
+      plugins: ['decorators-legacy'],
+    }).plugins
+  ).not.toSatisfyAny(isDecoratorsPlugin)
 })
 
 test('enables `topLevelAwait` even if `allowAwaitOutsideFunction` is disabled', () => {