How To Test NPM Packages Locally

Learn how to test your npm modules locally before publishing them to the npm registry. Follow this step-by-step guide to ensure your module works as expected and avoid potential issues when sharing it with the community.

Introduction

When developing an npm module, it’s crucial to test it thoroughly before publishing it to the npm registry. By testing your module locally, you can identify and fix any bugs or issues before making it available to others. This post will guide you through the process of testing npm modules locally, ensuring your module performs as expected.

Step 1: Creating a Module for Converting Strings to Title Case

To demonstrate the testing process, let’s create a module that converts a string to title case. Follow these steps:

1. Initialize your project by running the following command in your terminal:

npm init -y
touch index.js

2. Create a new file named index.js in your project folder.

3. Open the index.js file in your preferred code editor and add the following code:
   

module.exports=function(str){
    return str[0].toUpperCase()+str.slice(1);
}

Step 2: Testing the Module Locally

To test your module locally, you can use the npm link command, which creates a symbolic link. Follow these steps:

1. Navigate to your module’s project folder in the terminal.

2. Run the following command to create a link:

cd titlecase
npm link

3. If the command runs successfully, you should see an output similar to the following:

C:\Users\lenovo\AppData\Roaming\npm\node_modules\titlecase -> F:\blog\modules\titlecase

Step 3: Using the Module in Your Main Project

To use the module in your main project, you need to link it. Follow these steps:

1. Navigate to your main project’s folder in the terminal.

2. Run the following command to link the module:

    npm link titlecase
   
   

3. If the command runs successfully, you should see an output similar to the following:

   F:\blog\modules\module-demo\node_modules\titlecase -> C:\Users\lenovo\AppData\Roaming\npm\node_modules\titlecase -> F:\blog\modules\titlecase

4. Now, you can use the module in your main project. Open the file where you want to use it and add the following code:

const titleCase=require('titlecase');
console.log(titleCase("hello"));

Conclusion:

Testing your npm modules locally before publishing them to the npm registry is essential to ensure their functionality and avoid potential issues. By following the steps outlined in this guide, you can confidently test your modules, identify any bugs, and make necessary improvements. Remember to thoroughly validate your module’s behavior and address any reported issues before sharing it with the community. Happy testing and module development!