NodeJS: How to test the npm package before releasing

Let's say you have a core package that is used in your app and mobile projects.

Now you need to do some changes, both in core and app.

In the process of local development, you should test that core is working correctly with app before the release.
You can use npm link, but from my experience, it's not always working as expected.

A better alternative is yalc. You can check it yourself, but shortly, as the package itself says:

Better workflow than npm | yarn link for package authors
After everything is working locally, you are ready to do a Pull Request.
But wait! The CI will fail because the new version of core is only available locally.

To fix this, we need a prerelease version of the core that will be installed in CI, or then other engineers will try it on their machines.

Let's, say the previous version of core was 1.0.1, and you are working on future 1.0.2.

Semver.org docs suggests to use 1.0.2-rc.1 (release candidate),
but this approach does not work well when you are working on a project where many engineers can release to core before you.

From my experience, the best is to have a prerelease version that is associated with some issue/ticket/task number in the format:

<current version>-<issue number>.<WIP version>

Example: 1.0.1-4605.0, 1.0.1-4605.1 ...

The important part before publishing such a prerelease version is to set a tag.
If you don't set a tag, the package will be published as latest,
and then someone will try to install the core package, it will get the wrong "latest" version which may still be WIP.

For this, you might use the dev tag.

So, the workflow

1. You do changes in core
2. Use the WIP version of core in app locally using yalc
3. When the task is ready:
   • Change the version of core: 1.0.1-4605.0
   • Publish the WIP version: npm publish --tag dev
   • Update the app with WIP version of core
   • Do move WIP prereleases if needed: 1.0.1-4605.1
4. Create PRs for both projects
5. When core PR is approved
   • Merge core
   • Set new version 1.0.2
   • Publish core: npm publish (latest tag is default)
6. Update app PR with new version of core
7. Merge app changes into master
8. Happy coding