Detail:
It was mention in your user guide that users are unable to add duplicate email address when they are both buyers. However, users might have typos and capitalise some parts of it which allow for duplicate email addresses with different casing. For gmail accounts, power@gmail.com is the same as poweR@gmail.com
Steps to reproduce:
- addbuyer n/XellerGuy p/99999999 e/power@gmail.com
- addbuyer n/XellerGuy p/99999998 e/poweR@gmail.com
Suggested fix:
Account for case insensitivity validation when checking email addresses.
Screenshots:

Detail:
It was mention in your user guide that users are unable to add duplicate email address when they are both buyers. However, users might have typos and capitalise some parts of it which allow for duplicate email addresses with different casing. For gmail accounts,
power@gmail.comis the same aspoweR@gmail.comSteps to reproduce:
Suggested fix:
Account for case insensitivity validation when checking email addresses.
Screenshots: