Why this function results in false?

Really basic question here, I’m new to JS and I’m trying to show a test message on a test website but this code returns always as false no matter if I test(true) or test(false)

function test(myTest) {
  if (myTest) {
    showMessage("True");
  }
  showMessage("False");
}

I’ve tried executing with the following:

test();
test(true);
test(false);

They all give out false