Error executing GRANT statement: ERROR 1064

I think you're probably trying to create a user, but to create a user, use create user instead of grant.The grant is used to grant permissions to the created user.

In previous versions of MySQL, users were also created with grant, but in recent versions, errors occurred.

I think you can do the following.

create user test_user1@'%' identified by'test1234';
grant all on*.* to test_user1@'%' with grant option;