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Stephen Cooper
Stephen Cooper

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Use npm pack to test your packages locally

When working with npm packages you often want to test your package without having to publish it to npm. This enables you to have a quicker feedback loop and keeps the number of published versions to a minimum.

This is where npm pack comes in.

First: Build your Package

Before you can use npm pack you must first build your package. So run your build command and check that this has completed successfully. In my use case, for @ag-grid-community/angular the command is:

community-modules/angular$ npm run build
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Second: Locate your Build Artifacts package.json

The important part of this step is to run npm pack in the correct folder location where the build artifact package.json is located. Depending on your project that may be the same folder as where you ran your build. For me though, with this Angular library that means navigating into the dist/ag-grid-angular folder as that is where the Angular library builds to.

community-modules/angular$ cd ./dist/ag-grid-angular
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Third: Pack your artifacts

Now it is time to package our build artifacts to enable us to produce a package that mimic what would be published to npm. We tell npm to pack it to our user folder ~ for ease.

community-modules/angular/dist/ag-grid-angular$ npm pack --pack-destination ~
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After this runs you will have the following file.

~/ag-grid-community-angular-27.0.0.tgz
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Fourth: Point package.json to your file

Now that we have this package we can test it in our application. To do this we update our package.json to point to the file that we produced in the previous step.

"dependencies": {
  "@ag-grid-community/angular": "file:~/ag-grid-community-angular-27.0.0.tgz"
}
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Then make sure you remember to re-install your packages after this update.

npm install
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Fifth: Test your package in your application

Now you can run your application using your packed dependency.
This enables you to test your package without having to publish it to npm for all the world to see.

Not only does this save us time by giving us a quicker feedback loop but it keeps our published packaged versions clean. This approach also gives us more confidence that our library is working as expected when installed into an application. We are more closely mimicking our users as opposed to testing against the raw source files.

Happy testing!


Stephen Cooper - Senior Developer at AG Grid
Follow me on Twitter @ScooperDev or Tweet about this post.

Top comments (7)

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abbasc52 profile image
Abbas Cyclewala • Edited

Great article! Just adding some more points which might be helpful.

You don't need to pack your library to test it.
Just point the package.json dependency to actual library folder instead of the packed version and do npm i once.
npm creates a link to actual folder inside node_modules

Saves you additional steps of packaging and installing it after every change in your test project

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scooperdev profile image
Stephen Cooper

Thanks for highlighting this use case. I have done this in the past but seemed to run into issues with the linking. Maybe I should give it another go though as does save a few steps.

However, I still like the additional confidence of working off the same item that will actually end up in npm.

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kuabhish profile image
Abhishek Kumar

How to do this. Can you explain with code. Please.

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scooperdev profile image
Stephen Cooper

The official docs have some examples of this with an explanation of what it does.

docs.npmjs.com/cli/v8/commands/npm...

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sarveshprajapati profile image
Sarvesh Prajapati

great article man

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Stephen Cooper

Thanks! I have come back to the draft a few times to remind myself so how to do it so thought I should share it.

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sarveshprajapati profile image
Sarvesh Prajapati

absolutely