function addPercentSign(val) {
  var inputNumber = parseFloat(val);

  if (inputNumber) {
    if (inputNumber < 50 || inputNumber > 100) {
      //see learningCurveFormatCheck
      return null;
    } else {
      var finalVal = inputNumber.toFixed(1);
      var finalOutput = finalVal + "%";

      return finalOutput;
    };
  };
};

module("String formatting");

test("Returns undefined for unparseable strings", function() {
	["foo", null, NaN, "0.0.0"]
    .forEach(function(result, i, arr) {
    	var result = addPercentSign(result);
    	strictEqual(result, undefined, arr[i] + " produces " + result);
    });
});

test("Returns null for values below 50 and above 100", function() {
	["0", "0.0", "25", "49.99999", "100.00000001", "10300", Infinity]
  	.forEach(function(result, i, arr) {
    	var result = addPercentSign(result);
    	strictEqual(result, null, arr[i] + " produces " + result);
    });
});

test("Appends a % sign for values between 50 and 100", function() {
	strictEqual(addPercentSign("51.0"), "51.0%");
	// ...
});

test("Appends a digit for values without one", function() {
	strictEqual(addPercentSign("51"), "51.0%");
	// ...
});

test("Removes and rounds digits for values with more than one", function() {
	strictEqual(addPercentSign("51.999"), "52.0%");
  	strictEqual(addPercentSign("51.06"), "51.1%");
	// ...
});

<link href="https://code.jquery.com/qunit/qunit-1.12.0.css" rel="stylesheet"/>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://code.jquery.com/qunit/qunit-1.12.0.js"></script>

<div id="qunit"></div>
<div id="qunit-fixture"></div>

function createInput() {
  return $('<input id="learningCurveInput" type="text" value="hello world"/>')
    .appendTo('#qunit-fixture');
}

module("Writing and reading to input", {})

test("writes to value", function(assert) {
  var $input = createInput();
  var result = "55";

  // Whatever you're using to set:
  // in your code, I read `control.learningCurve.setValue`
  // if that's what you're using, that's the method you should test
  $input.val(result);

  strictEqual($input.val(), result);
});

test("reads from value", function(assert) {
  var $input = createInput();
  
  // Whatever you're using to get the value
  $input.val();

  strictEqual($input.val(), "hello world");
});

<link href="https://code.jquery.com/qunit/qunit-1.12.0.css" rel="stylesheet"/>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://code.jquery.com/qunit/qunit-1.12.0.js"></script>

<div id="qunit"></div>
<div id="qunit-fixture"></div>

function createForm() {
  return $("<form></form>")
    .append(createInput());
}

function createInput() {
  return $('<input id="learningCurveInput" type="text" value="hello world"/>')
    .appendTo('#qunit-fixture');
}

module("Form event listeners", {})

test("input executes method on change", function(assert) {
  var called = false;
  var onChange = function() { called = true; };
  var $input = createInput();
  $input.change(onChange);
  
  $input.val("test");
  strictEqual(called, false);
  
  $input.change();
  strictEqual(called, true);
  
});

test("form executes method on submit", function(assert) {
  var called = false;
  var onSubmit = function() { called = true; };
  var $form = createForm();
  var $input = $form.find("input");
  
  $form.submit(onSubmit);
  
  strictEqual(called, false);
  
  $form.submit();
  strictEqual(called, true);
  
});

<link href="https://code.jquery.com/qunit/qunit-1.12.0.css" rel="stylesheet"/>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://code.jquery.com/qunit/qunit-1.12.0.js"></script>

<div id="qunit"></div>
<div id="qunit-fixture"></div>