const expect = require('expect');
const chunk = require('./chunk.js');

test('chunk is a Function', () => {
  expect(chunk).toBeInstanceOf(Function);
});
test('chunk([1, 2, 3, 4, 5], 2) returns [[1,2],[3,4],[5]] ', () => {
  expect(chunk([1, 2, 3, 4, 5], 2)).toEqual([[1,2],[3,4][5]]);
});
test('chunk([]) returns []', () => {
  expect(chunk([])).toEqual([])
});
test('chunk(123) returns []', () => {
  expect(chunk(123)).toEqual([])
});
test('chunk({ a: 123}) returns []', () => {
  expect(chunk({ a: 123})).toEqual([])
});
test('chunk(string, 2) returns [ st, ri, ng ]', () => {
  expect(chunk('string', 2)).toEqual( [ 'st', 'ri', 'ng' ])
});
test('chunk() throws an error', () => {
  expect(chunk()).toThrow();
});
test('chunk(undefined) throws an error', () => {
  expect(chunk(undefined)).toThrow();
});
test('chunk(null) throws an error', () => {
  expect(chunk(null)).toThrow();
});
let start = new Date().getTime();
chunk('This is a string', 2);
let end = new Date().getTime();
test('chunk(This is a string, 2) takes less than 2s to run', () => {
  expect((end - start) < 2000).toBeTruthy();
});