w3bdesign / exercism

import { steps } from './collatz-conjecture';

describe('steps()', () => {

  test('zero steps for one', () => {

    expect(steps(1)).toEqual(0);

  });

  test('divide if even', () => {

    expect(steps(16)).toEqual(4);

  });

  test('even and odd steps', () => {

    expect(steps(12)).toEqual(9);

  });

  test('Large number of even and odd steps', () => {

    expect(steps(1000000)).toEqual(152);

  });

  test('zero is an error', () => {

    expect(() => {

      steps(0);

    }).toThrow(new Error('Only positive numbers are allowed'));

  });

 test('negative value is an error', () => {

    expect(() => {

      steps(-15);

    }).toThrow(new Error('Only positive numbers are allowed'));

  });

});