Student Management System Test

import static org.junit.jupiter.api.Assertions.*;

import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;

class StudentManagementSystemTest {

    private StudentManagementSystem sms;

    @BeforeEach
    void setUp() {
        sms = new StudentManagementSystem();
        sms.addStudent(1, "John Doe", 20);
        sms.addStudent(2, "Jane Smith", 21);
    }

    // Positive Test Cases

    @Test
    void testAddStudentSuccessfully() {
        sms.addStudent(3, "Alice Johnson", 22);
        assertNotNull(sms.studentMap.get(3), "Alice should be added successfully");
    }

    @Test
    void testAddGradeToStudentSuccessfully() {
        sms.addGradeToStudent(1, 85);
        sms.addGradeToStudent(1, 90);
        assertEquals(87.5, sms.studentMap.get(1).calculateAverageGrade(), 0.001, "John's average should be 87.5");
    }

    @Test
    void testUpdateAttendanceSuccessfully() {
        sms.updateStudentAttendance(1, 25);
        assertEquals(25, sms.studentMap.get(1).attendance, "John's attendance should be 25");
    }

    @Test
    void testCalculateAverageGradeCorrectly() {
        sms.addGradeToStudent(2, 70);
        sms.addGradeToStudent(2, 80);
        assertEquals(75.0, sms.studentMap.get(2).calculateAverageGrade(), 0.001, "Jane's average should be 75.0");
    }

    @Test
    void testPerformanceAssessment() {
        sms.addGradeToStudent(1, 95);
        sms.addGradeToStudent(1, 92);
        assertEquals("Excellent", sms.studentMap.get(1).getPerformance(), "John's performance should be Excellent");
    }

    // Negative Test Cases

    @Test
    void testAddStudentWithDuplicateId() {
        sms.addStudent(1, "Duplicate John", 23);
        assertEquals("John Doe", sms.studentMap.get(1).name, "Original student should not be overwritten");
    }

    @Test
    void testAddGradeToNonExistentStudent() {
        Exception exception = assertThrows(NullPointerException.class, () -> {
            sms.addGradeToStudent(5, 80);
        });
        assertNotNull(exception, "Adding grade to non-existent student should throw exception");
    }

    @Test
    void testUpdateAttendanceForNonExistentStudent() {
        Exception exception = assertThrows(NullPointerException.class, () -> {
            sms.updateStudentAttendance(99, 30);
        });
        assertNotNull(exception, "Updating attendance for non-existent student should throw exception");
    }

    @Test
    void testCalculateAverageWithoutGrades() {
        double avg = sms.studentMap.get(2).calculateAverageGrade();
        assertEquals(0.0, avg, "Average should be 0.0 if no grades are added");
    }

    @Test
    void testPerformanceWithoutGrades() {
        String performance = sms.studentMap.get(2).getPerformance();
        assertEquals("Needs Improvement", performance, "Performance should be 'Needs Improvement' if no grades exist");
    }

    @Test
    void testAddNegativeGrade() {
        sms.addGradeToStudent(1, -50); // Logically wrong but allowed in current system
        double avg = sms.studentMap.get(1).calculateAverageGrade();
        assertTrue(avg < 0, "Average should reflect negative grade if system doesn't prevent it");
    }

    @Test
    void testZeroAttendance() {
        sms.updateStudentAttendance(1, 0);
        assertEquals(0, sms.studentMap.get(1).attendance, "Attendance should be 0 if updated as 0");
    }
}