How to test the equivalence splitting method of the user authentication process?

Question

Software testing

I can't figure out how to create equivalence classes. The authentication process is very simple. The user enters an email and password, if the email exists in the database, matches the pattern and the password is correct, then we load the user's main page. If he logs in for the first time, but his email is in the database, then we ask him to re-enter the password entered for the first time and overwrite the password in the database. In all other cases, we issue an error message. How can all this be broken down into equivalence classes and what should be the test options?

Answer 1

classes for email:
1. email exists in the database, matches the pattern and the user has already logged in
2. email exists in the database, but the user is logging in for the first time
3. email is incorrect:
a) does not exist in the database
b) does not match
password pattern :
1. correct
2. incorrect
if there are additional restrictions on the password, then it is still broken
Test options: various combinations of classes (well, if I remember correctly, you can not combine a bad option with a bad one)