Missing Bootstrap class "input-group-addon" in Laravel 5.6 project

Hi,

I'm currently struggling with a really strange issue dealing with the pre installed bootstrap 4 version in a Laravel 5.6 project.

I'm building a form, and trying to use something like this

  <div class="form-group">
        <div class="input-group input-group-lg">
                 <span class="input-group-addon"><i class="fa fa-user"></i></span>
                 <input type="text" class="form-control" placeholder="Name">
        </div>
</div>

The issue is that the class input-group-addon isn't recognized in the browser..

When I browse bootstrap.min.css in my project, I end up with 2 files.

One with the path:

 "node_modules/bootstrap/dist/css/bootstrap.min.css" 

And this one has the actual class and the second one in

"vendor/phpunit/php-code-coverage/src/Report/Html/Renderer/Template/css/bootstrap.min.css" 

doesn't have this class.

Since I don't know much about Webpack, babel and stuff like that, I dont even know which one is being loaded in my app.scss file

Here's the code :

@import '~bootstrap/scss/bootstrap';

Could anyone explain to me what's happening there please, and so I can load the correct bootstrap with the input-group-addon class as it should normally be.

Thanks