I cannot call a function in another JavaScript file

I have two JavaScript files on my custom theme. One file has functions that need to be used on the other file. What I have below doesn't work. This is the error I get.

Uncaught ReferenceError: test is not defined.

jQuery will be used on both files.

file1.js

/**
 * @file
 * UI behaviors
 */

(function ($, Drupal) {

 'use strict';

  $(document).ready(function () {
    function test(){
     console.log('hello'):
    }
  });

})(jQuery, Drupal);

file2.js

/**
 * @file
 * UI behaviors
 */

(function ($, Drupal) {

  'use strict';

  $(document).ready(function () {
     test();
  });

})(jQuery, Drupal);

customtheme.libraries.yml

scripts:
  js:
    js/file1.js: {}
    js/file2.js: {}

customtheme.info.yml

libraries:
 - 'customtheme/scripts'

This is because test() is wrapped in an anonymous function, making it not available outside of that function.

I would add it to the Drupal object:

File 1:

(function($, Drupal) {
  Drupal.myFunction = function() {
    // Do something.
  }
}(jQuery, Drupal));

File 2:

(function($, Drupal) {
  Drupal.myFunction();
});

Also, as a side note, $(document).ready() is not used in Drupal. In Drupal Drupal.behaviors is used instead: https://www.drupal.org/docs/drupal-apis/javascript-api/javascript-api-overview