Add student when semester is negative

[manhtthe]

Test Case ID: TS_SMS_007, TS_SMS_StudentManagmentSystem_006

When add student, user enters semester is negative but add succeeds

Steps to Reproduce:

1. Log in successfully with an authorized account
2. Access the student page, select add student
3. Enter a valid Student Name: User enters the correct Student Name
4. Enter a valid Student Code: User enters the correct Student Code
5. Enter incorrect Semester: User enters Semester as a negative number
6. Enter a valid Email: User enters the correct Email
7. Enter a valid Password: User enters the correct Password
8. Enter a valid Address: User enters the correct Address
9. Enter a valid Phone Number: User enters the correct Phone Number
10. Enter a valid Gender: User enters the correct Gender
11. Enter a valid DOB: User enters the correct DOB
12. Enter a valid ClassRoom: User enters the correct ClassRoom
13. Select status : User selects status for student
14. Click the save button: User clicks the "Save" button.

Expected Result: The system returns the message "Semester là số không âm" and asks the user to re-enter

[manhtthe]

Check input when entering semester