completed part one of junit tests exercise

src/main/java/Student.java

@@ -0,0 +1,58 @@
+import java.util.ArrayList;
+import java.util.List;
+
+public class Student {
+
+    private long id;
+    private String name;
+    private ArrayList<Integer> grades;
+
+    public Student(long id, String name) {
+        this.id = id;
+        this.name = name;
+        this.grades = new ArrayList<>();
+    }
+
+    // returns the student's id
+    public long getId() {
+        return id;
+    }
+
+    // returns the student's name
+    public String getName() {
+        return name;
+    }
+
+    public List<Integer> getGrades() {
+        return grades;
+    }
+
+    // adds the given grade to the grades list
+    public void addGrade(int grade) {
+        grades.add(grade);
+    }
+
+    // returns the average of the students grades
+    public double getGradeAverage() {
+        if (grades.isEmpty()) {
+            return 0.0;
+        }
+        int sum = 0;
+        for (int grade : grades) {
+            sum += grade;
+        }
+        return (double) sum / grades.size();
+    }
+
+    public void updateGrade(int index, int newGrade) {
+        if (index >= 0 && index < grades.size()) {
+            grades.set(index, newGrade);
+        }
+    }
+
+    public void deleteGrade(int index) {
+        if (index >= 0 && index < grades.size()) {
+            grades.remove(index);
+        }
+    }
+}

src/test/java/StudentTest.java

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+import org.junit.Test;
+import static org.junit.Assert.*;
+import java.util.ArrayList;
+
+public class StudentTest {
+    @Test
+    public void testStudentConstructorAndGetters() {
+        long id = 123456789;
+        String name = "Jimmy John";
+        Student student = new Student(id, name);
+
+        assertEquals(id, student.getId());
+        assertEquals(name, student.getName());
+        assertEquals(new ArrayList<Integer>(), student.getGrades());
+    }
+
+    @Test
+    public void testAddGradeAndGetGradeAverage() {
+        Student student = new Student(123456789, "Jimmy John");
+
+        student.addGrade(80);
+        assertEquals(80, student.getGrades().get(0).intValue());
+        assertEquals(80.0, student.getGradeAverage(), 0.001);
+
+        student.addGrade(90);
+        assertEquals(90, student.getGrades().get(1).intValue());
+        assertEquals(85.0, student.getGradeAverage(), 0.001);
+    }
+
+    @Test
+    public void testUpdateGrade() {
+        Student student = new Student(123456789, "Jimmy John");
+        student.addGrade(80);
+        student.addGrade(90);
+
+        student.updateGrade(1, 95);
+        assertEquals(95, student.getGrades().get(1).intValue());
+        assertEquals(87.5, student.getGradeAverage(), 0.001);
+    }
+
+    @Test
+    public void testDeleteGrade() {
+        Student student = new Student(123456789, "Jimmy John");
+        student.addGrade(80);
+        student.addGrade(90);
+
+        student.deleteGrade(0);
+        assertEquals(90, student.getGrades().get(0).intValue());
+        assertEquals(90.0, student.getGradeAverage(), 0.001);
+    }
+}