test(sorting): add student record book case

app/src/test/java/ru/project/sorting/EvenOnlyMergeSortStrategyTest.java

@@ -3,6 +3,7 @@ package ru.project.sorting;
 import org.junit.jupiter.api.Test;
 import ru.project.collection.MyLinkedList;
 import ru.project.collection.MyList;
+import ru.project.student.Student;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
@@ -144,6 +145,33 @@ class EvenOnlyMergeSortStrategyTest {
         assertEquals(5, list.get(4));
         assertEquals(2, list.get(5));
     }
+
+    @Test
+    void shouldUseStudentRecordBookNumberToDetermineEvenElements() {
+        MyList<Student> students = new MyLinkedList<>();
+
+        students.add(new Student("A01", 4.0, 7));
+        students.add(new Student("A02", 4.0, 8));
+        students.add(new Student("A03", 4.0, 3));
+        students.add(new Student("A04", 4.0, 2));
+        students.add(new Student("A05", 4.0, 5));
+        students.add(new Student("A06", 4.0, 4));
+
+        SortStrategy<Student> strategy = new EvenOnlyMergeSortStrategy<>(
+                Student::getRecordBookNumber
+        );
+
+        strategy.sort(students, new StudentRecordBookComparator());
+
+        assertEquals(7, students.get(0).getRecordBookNumber());
+        assertEquals(2, students.get(1).getRecordBookNumber());
+        assertEquals(3, students.get(2).getRecordBookNumber());
+        assertEquals(4, students.get(3).getRecordBookNumber());
+        assertEquals(5, students.get(4).getRecordBookNumber());
+        assertEquals(8, students.get(5).getRecordBookNumber());
+
+        assertEquals(6, students.size());
+    }
 }