text: const main = require('./main');
  
  // toBe, toBeNull, toBeUndefined
  test('Checking the test', function(){
      expect(main.add(2,2)).toBe(4);
      expect(main.isNull()).toBeNull();
      expect(main.isUndefined()).toBeUndefined();
  });
  
  // toBeFalse
  test('Should be falsy', () => {
      expect(main.checkValue(0)).toBeFalsy()
  })
  
  // User should be Shabuktagin Khan Object
  test('User should be Shabuktagin Khan', () => {
      expect(main.createUser()).toEqual({
          firstName: "Shabuktagin",
          lastName: "Khan"
      });
  });
  
  // Greater Than or Less than
  test("Should be under 16", () => {
      let num1 = 10;
      let num2 = 3;
      expect(num1 + num2).toBeLessThanOrEqual(16);
  });
  
  // Regular Expression
  test('there is no I in team', () => {
      expect('team').not.toMatch(/I/);
  });
  
  test('but there is a "stop" in Christoph', () => {
      expect('Christoph').toMatch(/stop/);
  });
  
  // Arrays
  test('Admin should be in usernames', () => {
      usernames = ['admin', 'hello', 'nyo'];
      expect(usernames).toContain('admin');
  });
  
  // Working with Asynchronous data
  test('User fetched name should be Leanne Graham', () => {
      expect.assertions(1);
      return main.fetchUser()
              .then(data => {
                  expect(data.name).toEqual('Leanne Graham')
              })
  });
  
  // Function exists or not
  test('Reverse string reverse function exists or not', () => {
      expect(main.stringReverse).toBeDefined();
  })
  
  test('Testing Reverse String works or not', () => {
      expect(main.stringReverse('hello')).toEqual('olleh');
  });