input: Write a python function to create a User object and test its properties.
  assert user1.name == 'John'
  assert user1.age == 30
  assert user2.name == 'Alice'
  assert user2.age == 25
  assert user3.name == 'Bob'
  try:
      user3.age = -5
  except ValueError as e:
      assert str(e) == 'Age must be a positive number'
output: class User:
      def __init__(self, name, age):
          self.name = name
          self.age = age
  
      @property
      def age(self):
          return self._age
  
      @age.setter
      def age(self, value):
          if value < 0:
              raise ValueError('Age must be a positive number')
          self._age = value
  
  user1 = User('John', 30)
  user2 = User('Alice', 25)
  user3 = User('Bob', 35)
  
  assert user1.name == 'John'
  assert user1.age == 30
  assert user2.name == 'Alice'
  assert user2.age == 25
  assert user3.name == 'Bob'
  try:
      user3.age = -5
  except ValueError as e:
      assert str(e) == 'Age must be a positive number'