const expect = require('expect');
const {collatz} = require('./_30s.js');

test('collatz is a Function', () => {
  expect(collatz).toBeInstanceOf(Function);
});
test('When n is even, divide by 2', () => {
  expect(collatz(8)).toBe(4);
});
test('When n is odd, times by 3 and add 1', () => {
  expect(collatz(9)).toBe(28);
});
test('Eventually reaches 1', () => {
  let n = 9;
  while (true) {
    if (n === 1) {
      expect(n).toBe(1);
      break;
    }
    n = collatz(n);
  }
});