Call external function in unit test

I'm trying to learn qunit test; I'm an OpenUi5 developer and I use Webstorm IDE every day. Webstorm allows me to config a Karma run configuration. I have created a simple karma configuration file and I have wrotten a test file test1.js:

test("Test function sum()",
  function() {
    ok(sum(0, 0) == 0, "the sum of 0 with 0 is 0");
    ok(sum(2, 0) == 2, "the sum of 2 with 0 is 2");
    ok(sum(2, 1) == 3, "the sum of 2 with 1 is 3");
    ok(sum(2, -1) == 1, "the sum of 2 with -1 is 1");
    ok(sum(-2, 1) == -1, "the sum of -2 with 1 is -1");
  });


function sum(a, b) {
  return a + b;
};

Good! sum fnction in inside the same file. But now I want start to test function in my js folder of projesct; for example in js/util.js I have getShortIdGrid function:

//util.js file
ui5bp.control = {
  ...
  getShortIdGrid: function(sFromId) {
      if (sFromId.lastIndexOf("_") < 0)
        return sFromId;
      else
        return sFromId.substring(0, sFromId.lastIndexOf("_"));
  },
  ...
}

How can I call ui5bp.controlgetShortIdGrid in my test?

Karma console show me ReferenceError: ui5bp is not defined