NX React - how to create default mock for library

user_12246420 0
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How do you create manual mock for your libs, which are used by your apps?

I'm trying to follow scope mocking in jest documentation but have no luck.

Example:

my-workspace
├── __mocks__
│   └── @my-workspace/my-lib.ts
├── apps
│   ├── my-app
│       └── index.ts
├── libs
│   ├── my-lib
│       └── index.ts
...
nomachine-nx nrwl jestjs reactjs
1 Answers

libs in an nx workspace can be imported like regular node_modules thanks to its TS path mapping (check your tsconfig.base.json to see how @workspace-scope/my-lib is being resolved).

However, your lib is not a node module per say (even if you publish it), and should be mocked using the "user modules" jest pattern instead: https://jestjs.io/docs/manual-mocks#mocking-user-modules

Move the mock to libs/my-lib/__mocks__/index.ts instead (you can split mocks into several files if you need, just make sure to export whatever you need to mock from the index file) then call jest.mock('@workspace-scope/my-lib'); manually in the spec file where you import your lib function:

// libs/my-lib/__mocks__/index.ts
export function foo(): string {
  return 'foo';
}

// apps/my-app/.../some-test.spec.ts
import { foo } from '@workspace-scope/my-lib';

// manually mock the user module: make sure the path matches the import above
jest.mock('@workspace-scope/mylib');
// --> now when you invoke foo() in this file, jest should invoke "foo" exported from "libs/my-lib/__mocks__/index.ts" instead

describe('test foo', () => {
  test('returns "foo"', () => {
    expect(foo()).toBe('foo');
  });
});
user_14609050
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