Lerna package import in CI

Question

I want to test my typescript library. It has two parts: core and client. client instance core to use its functions.

import { Core } from "@lib/core";
class Client {
  constructor() {
    new Core();
  }
}

To make these two parts independent, I use lerna as if they were separated npm packages: @lib/core and @lib/client.

Everything runs ok in local environment, but in gitlab CI this error is thrown before the client tests start:

Cannot find module '@lib/core' from 'src/lib/client.spec.ts'
      3 |
    > 4 | jest.mock('@lib/core');
        |      ^

lerna.json

{
  "packages": ["packages/core", "packages/client"],
  "version": "independent",
  "npmClient": "npm"
}

.gitlab-ci.yml

image: node:14

cache:
  paths:
    - node_modules
    - '**/node_modules'
    - .npm
    - dist

---
unit:
  stage: test
  script:
    - npx jest --clear-cache
    - npm run test

---

Inside packages/client I have a node_modules folder with a symlink to @lib/core.

packages
├── client
│   ├── ng-package.json
│   ├── node_modules
│   │   └── @lib
│   │       └── core -> ../../../core
│   ├── package-lock.json
│   ├── package.json
│   └── src
│       ├── lib
│       │   ├── client.ts
│       └── public-api.ts
└── core
    ├── ng-package.json
    ├── package-lock.json
    ├── package.json
    └── src
        ├── lib
        │   ├── core.ts
        └── public-api.ts

When the code is compiled, in dist folder there are the two libraries (client, core). Inside the compiled code of client, the reference to core is like this: require('@lib/core').

In local environment it works because I have these paths in tsconfig:

"paths": {
      "@lib/core": ["dist/core"],
      "@lib/client": ["dist/client"]
}

In ci it tries to download lib/core from the registry and it does not exist.

I would like to make client import core code and provide only one library (all together). So the import of core is transparent to the final user.