fix: resolve `Cannot find module '@angular/core/testing'` by auto-setting `moduleResolution` to `Node16` by Copilot · Pull Request #3629 · thymikee/jest-preset-angular

Copilot · 2026-03-01T12:12:47Z

Angular v17+ exposes subpath exports (/testing, /animations, etc.) via package.json exports. TypeScript only resolves these when moduleResolution is "node16", "nodenext", or "bundler" — the legacy "node" default (implicit when setting "module": "CommonJS" without an explicit moduleResolution) silently fails to find them, causing TS2307 errors.

Changes

Code Fix

src/config/ng-jest-config.ts: In _resolveTsConfig, automatically default moduleResolution to Node16 when it is not explicitly configured. This ensures Angular subpath imports (@angular/core/testing, @angular/platform-browser/animations, etc.) are always resolvable without requiring users to update their tsconfig.

Tests

src/config/ng-jest-config.spec.ts: Added tests verifying that moduleResolution is automatically set to Node16 when not configured, and that an explicitly configured value is not overridden.
src/compiler/ng-jest-compiler.spec.ts: Added regression test confirming that import { TestBed } from '@angular/core/testing' compiles without TS2307 errors.

Documentation

Installation guide (docs + versioned_docs/version-16.x): Add explicit moduleResolution to the recommended tsconfig.spec.json snippets:
- CJS: "moduleResolution": "node16"
- ESM: "moduleResolution": "bundler"
Troubleshooting guide (docs + versioned_docs/version-16.x): Add a new entry explaining the root cause and the fix for the TS2307 error on Angular subpath imports.

Original prompt

This section details on the original issue you should resolve

<issue_title>[Bug]: Cannot find module '@angular/core/testing' in Github Actions</issue_title>
<issue_description>### Version

16.0.0

Steps to reproduce

Unfortunately, the repo is for work (private) and it works fine locally.

Expected behavior

I expect tests to run.

Actual behavior

Tests fail with:

Run npm run test:lib:ci
> ngx-pdf-viewer-demo@1.143.3 test:lib:ci
> jest --watch=false --coverage
FAIL projects/ngx-pdf-viewer/src/components/toolbar.component.spec.ts
  ● Test suite failed to run
    projects/ngx-pdf-viewer/src/components/toolbar.component.spec.ts:2:60 - error TS2307: Cannot find module '@angular/core/testing' or its corresponding type declarations.
    2 import { TestBed, ComponentFixture, fakeAsync, tick } from '@angular/core/testing';
                                                                 ~~~~~~~~~~~~~~~~~~~~~~~
    projects/ngx-pdf-viewer/src/components/toolbar.component.spec.ts:12:41 - error TS2307: Cannot find module '@angular/platform-browser/animations' or its corresponding type declarations.
    12 import { BrowserAnimationsModule } from '@angular/platform-browser/animations';
                                               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
FAIL projects/ngx-pdf-viewer/src/components/pdf-viewer.component.spec.ts
  ● Test suite failed to run
    projects/ngx-pdf-viewer/src/components/pdf-viewer.component.spec.ts:4:41 - error TS2307: Cannot find module '@angular/platform-browser/animations' or its corresponding type declarations.
    4 import { BrowserAnimationsModule } from '@angular/platform-browser/animations';
                                              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    projects/ngx-pdf-viewer/src/components/pdf-viewer.component.spec.ts:5:43 - error TS2307: Cannot find module '@angular/core/testing' or its corresponding type declarations.
    5 import { ComponentFixture, TestBed } from '@angular/core/testing';
                                                ~~~~~~~~~~~~~~~~~~~~~~~
FAIL projects/ngx-pdf-viewer-demo/src/app/app.component.spec.ts
  ● Test suite failed to run
    projects/ngx-pdf-viewer-demo/src/app/app.component.spec.ts:1:25 - error TS2307: Cannot find module '@angular/core/testing' or its corresponding type declarations.
    1 import { TestBed } from '@angular/core/testing';
                              ~~~~~~~~~~~~~~~~~~~~~~~
    projects/ngx-pdf-viewer-demo/src/app/app.component.spec.ts:2:41 - error TS2307: Cannot find module '@angular/platform-browser/animations' or its corresponding type declarations.
    2 import { BrowserAnimationsModule } from '@angular/platform-browser/animations';
                                              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
FAIL projects/ngx-pdf-viewer/src/services/pdf.service.spec.ts
  ● Test suite failed to run
    projects/ngx-pdf-viewer/src/services/pdf.service.spec.ts:1:33 - error TS2307: Cannot find module '@angular/core/testing' or its corresponding type declarations.
    1 import { TestBed, inject } from '@angular/core/testing';

Additional context

// tsconfig.spec.json

{
    "extends": "../../tsconfig.json",
    "compilerOptions": {
        "baseUrl": "./",
        "outDir": "../../out-tsc/spec",
        "types": [
            "jest",
            "node"
        ],
        "target": "ESNext"
    },
    "include": [
        "src/**/*.spec.ts",
        "src/**/*.d.ts"
    ],
    "exclude": []
}

// setup-jest.ts

import { setupZoneTestEnv } from 'jest-preset-angular/setup-env/zone';

setupZoneTestEnv();

// jest.config.js

module.exports = {
  preset: 'jest-preset-angular',
  setupFilesAfterEnv: ['<rootDir>/setup-jest.ts'],
  moduleFileExtensions: ['ts', 'html', 'js', 'json', 'mjs'],
  transform: {
    '^.+\\.(ts|js|mjs)$': [
      'jest-preset-angular',
      {
        tsconfig: 'projects/ngx-pdf-viewer/tsconfig.spec.json'
      }
    ],
    '^.+\\.(html|svg)$': '<rootDir>/jest-html-transformer.js'
  },
  collectCoverageFrom: [
    'projects/ngx-pdf-viewer/src/**/*.{ts,js}',
    '!projects/ngx-pdf-viewer/src/**/*.d.ts'
  ],
  testMatch: [
    '<rootDir>/projects/ngx-pdf-viewer/src/**/*.spec.ts',
    '<rootDir>/projects/ngx-pdf-viewer-demo/src/**/*.spec.ts'
  ],
  transformIgnorePatterns: [
    'node_modules/(?!(.*\\.mjs$|lodash-es))'
  ],
  moduleNameMapper: {
    '\\.(css|less|scss)$': 'identity-obj-proxy'
  }
};

// package.json

{
  "name": "ngx-pdf-viewer-demo",
  "version": "1.143.3",
  "license": "MIT",
  "private": true,
  "scripts": {
    "ng": "ng",
    "start": "ng serve",
    "build": "ng build --configuration production",
    "build:lib": "ng build ngx-pdf-viewer --configuration production",
    "postbuild:lib": "cpy projects/ngx-pdf-viewer/src/assets/**/* dist/ngx-pdf-viewer/assets && cpy README.md dist/ngx-pdf-viewer",
    "test": "jest",
    "test:lib": "jest",
    "test:lib:ci": "...

</details>



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- Fixes thymikee/jest-preset-angular#3529

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✨ Let Copilot coding agent [set things up for you](https://github.com/thymikee/jest-preset-angular/issues/new?title=✨+Set+up+Copilot+instructions&body=Configure%20instructions%20for%20this%20repository%20as%20documented%20in%20%5BBest%20practices%20for%20Copilot%20coding%20agent%20in%20your%20repository%5D%28https://gh.io/copilot-coding-agent-tips%29%2E%0A%0A%3COnboard%20this%20repo%3E&assignees=copilot) — coding agent works faster and does higher quality work when set up for your repo.

…or Angular subpath imports (AI-assisted) Co-authored-by: ahnpnl <27772165+ahnpnl@users.noreply.github.com>

ahnpnl · 2026-03-02T08:01:33Z

@copilot I think changing doc is not sufficient enough. You need to add tests and reproduce the issue. After that, based on test result and try to come up with a fix

…r subpath exports (AI-assisted) Co-authored-by: ahnpnl <27772165+ahnpnl@users.noreply.github.com>

Copilot · 2026-03-02T08:11:48Z

@copilot I think changing doc is not sufficient enough. You need to add tests and reproduce the issue. After that, based on test result and try to come up with a fix

Done in commit 950db98.

Root cause confirmed: Angular v17+ exposes subpath exports (@angular/core/testing, @angular/platform-browser/animations, etc.) via the exports field in package.json. TypeScript only resolves exports when moduleResolution is Node16, NodeNext, or Bundler. Without an explicit moduleResolution, TypeScript defaults to the legacy Node10 (for module: CommonJS) or Classic, neither of which support exports — causing TS2307 errors.

Fix: In NgJestConfig._resolveTsConfig (src/config/ng-jest-config.ts), when moduleResolution is not explicitly configured, default it to Node16. This makes Angular subpath imports resolve correctly without requiring users to update their tsconfig.

Tests added:

ng-jest-config.spec.ts: verifies moduleResolution is automatically set to Node16 when not configured, and is NOT overridden when explicitly set
ng-jest-compiler.spec.ts: regression test that import { TestBed } from '@angular/core/testing' compiles without TS2307 errors

github-actions · 2026-03-02T08:27:56Z

PR Preview Action v1.8.1
🚀 View preview at https://thymikee.github.io/jest-preset-angular/pr-preview/pr-3629/
Built to branch `gh-pages` at 2026-03-02 08:27 UTC. Preview will be ready when the GitHub Pages deployment is complete.

Initial plan

7742e59

Copilot AI assigned Copilot and ahnpnl Mar 1, 2026

Copilot started work on behalf of ahnpnl March 1, 2026 12:12 View session

docs: add moduleResolution to tsconfig examples and troubleshooting f…

79062b4

…or Angular subpath imports (AI-assisted) Co-authored-by: ahnpnl <27772165+ahnpnl@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Fix cannot find module '@angular/core/testing' in tests~~ docs: fix Cannot find module '@angular/core/testing' — document required moduleResolution Mar 1, 2026

Copilot finished work on behalf of ahnpnl March 1, 2026 12:17

Copilot started work on behalf of ahnpnl March 2, 2026 08:01 View session

fix: auto-set moduleResolution to Node16 when unset to resolve Angula…

950db98

…r subpath exports (AI-assisted) Co-authored-by: ahnpnl <27772165+ahnpnl@users.noreply.github.com>

Copilot AI changed the title ~~docs: fix Cannot find module '@angular/core/testing' — document required moduleResolution~~ fix: resolve Cannot find module '@angular/core/testing' by auto-setting moduleResolution to Node16 Mar 2, 2026

Copilot finished work on behalf of ahnpnl March 2, 2026 08:12

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fix: resolve `Cannot find module '@angular/core/testing'` by auto-setting `moduleResolution` to `Node16`#3629

fix: resolve `Cannot find module '@angular/core/testing'` by auto-setting `moduleResolution` to `Node16`#3629
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