input: Write a python function to create a MySQL database and table using mysql.connector.
  assert create_database_and_table() == "Database and table created successfully"
  assert isinstance(create_database_and_table(), str)
output: import mysql.connector
  from mysql.connector import errorcode
  
  def create_database_and_table():
      try:
          # Connect to MySQL server
          cnx = mysql.connector.connect(user='your_user', password='your_password')
          cursor = cnx.cursor()
          
          # Create database
          cursor.execute("CREATE DATABASE IF NOT EXISTS testdb")
          
          # Connect to the newly created database
          cnx.database = 'testdb'
          
          # Create table
          create_table_query = """
          CREATE TABLE IF NOT EXISTS test_table (
              id INT AUTO_INCREMENT PRIMARY KEY,
              name VARCHAR(255) NOT NULL,
              age INT NOT NULL
          )
          """
          cursor.execute(create_table_query)
          
          # Commit changes and close connections
          cnx.commit()
          cursor.close()
          cnx.close()
          
          return "Database and table created successfully"
      except mysql.connector.Error as err:
          if err.errno == errorcode.ER_ACCESS_DENIED_ERROR:
              return "Something is wrong with your user name or password"
          elif err.errno == errorcode.ER_BAD_DB_ERROR:
              return "Database does not exist"
          else:
              return err