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

test('isNil is a Function', () => {
  expect(isNil).toBeInstanceOf(Function);
});
test('Returns true for null', () => {
  expect(isNil(null)).toBeTruthy();
});
test('Returns true for undefined', () => {
  expect(isNil(undefined)).toBeTruthy();
});
test('Returns false for an empty string', () => {
  expect(isNil('')).toBeFalsy();
});