Hi Unnati, you can use TestNG to write test script for your requirements. Following test script fulfills your requirements:
@test
public void testAdminUserCanUpdateUserAccountPassword() {
 // create users 
 User userAdmin = new User(UserRole.ADMIN, username, password);
 User user = new User(UserRole.VIEWER, user_username, user_password);
       
 // use Admin user to update another user password
  String message = userAdmin.updatePassword(user, user_new_password);
  
// verify password changed
  Assert.assertEquals(message, "Password changed successfully");
  Assert.assertEquals(user.getPassword(), user_new_password);
}