kata from TDD workshop

kata.test.js

// FUNCTION
const add = (input) => {
  if (input=="")return 0;
  input = input.substr(2,input.lenght);
  var numbers=input.split(/\D+/g).map((num) => parseInt(num));
  var sum = 0;
  for (var i = 0; i < numbers.length; i++) {
    sum += numbers[i];
  }
  return sum;
}

test('When it has 0 arguments will return 0', ()=>{
  expect(add('')).toBe(0);
});

test('When it has 1 argument will return the value of this argument', ()=>{
  expect(add('5')).toBe(5);
});

test('When it has 2 arguments will return the sum of these arguments', ()=>{
  expect(add('5,6')).toBe(11);
});

test('When it has seven number of arguments will return the sum of these arguments', ()=>{
  expect(add('1,2,3,4,5,6,7')).toBe(28);
});

test('When the values are separated with new line it should work', ()=>{
  expect(add('1\n2,3')).toBe(6);
});

test('When the values are separated with special separator it should work', ()=>{
  expect(add("//;\n1;2")).toBe(3);
});