refactoring: extract temporary file handling into methods in CourseTest file

src/test/java/org/example/CourseTest.java

@@ -1,6 +1,6 @@
 package org.example;
+
 import org.junit.jupiter.api.Test;
-import static org.junit.jupiter.api.Assertions.*;
 import java.io.ByteArrayOutputStream;
 import java.io.PrintStream;
 import static org.junit.Assert.assertEquals;
@@ -9,6 +9,7 @@ import java.util.List;
 
 
 class CourseTest {
+    private static final String TEMP_FILE = "test_course_data.txt";
 
     @Test
     void printCourseInfo() {
@@ -45,48 +46,33 @@ class CourseTest {
 
     @Test
     void writeToFile() {
-        // Create a temporary file for testing
-        String filename = "test_course_data.txt";
-
         // Create a new course
         Course course = new Course("Math", "C101", 3);
 
         // Write course data to the temporary file
-        course.writeToFile(filename);
+        course.writeToFile(TEMP_FILE);
 
         // Read course data from the temporary file
-        List<Course> courses = Course.readFromFile(filename);
+        List<Course> courses = Course.readFromFile(TEMP_FILE);
 
         // Assert that the read data matches the original course
         assertEquals(1, courses.size());
         Course readCourse = courses.get(0);
         assertEquals("Math", readCourse.getCourseName());
+        assertEquals("C101", readCourse.getCourseCode());
         assertEquals(3, readCourse.getCourseCredit());
 
         // Delete the temporary file
-        File file = new File(filename);
-        if (file.exists()) {
-            file.delete();
-        }
+        deleteTempFile();
     }
 
     @Test
     void readFromFile() {
         // Create a temporary file with sample course data
-        String filename = "test_course_data.txt";
-        try (PrintWriter writer = new PrintWriter(new FileWriter(filename))) {
-            writer.println("Math");
-            writer.println("C101");
-            writer.println(3);
-            writer.println("Science");
-            writer.println("C201");
-            writer.println(4);
-        } catch (IOException e) {
-            e.printStackTrace();
-        }
+        createTempFile("Math", "C101", "3", "Science", "C201", "4");
 
         // Read course data from the temporary file
-        List<Course> courses = Course.readFromFile(filename);
+        List<Course> courses = Course.readFromFile(TEMP_FILE);
 
         // Assert that the read data matches the original course data
         assertEquals(2, courses.size());
@@ -102,7 +88,21 @@ class CourseTest {
         assertEquals(4, course2.getCourseCredit());
 
         // Delete the temporary file
-        File file = new File(filename);
+        deleteTempFile();
+    }
+
+    private void createTempFile(String... data) {
+        try (PrintWriter writer = new PrintWriter(new FileWriter(TEMP_FILE))) {
+            for (String line : data) {
+                writer.println(line);
+            }
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+
+    private void deleteTempFile() {
+        File file = new File(TEMP_FILE);
         if (file.exists()) {
             file.delete();
         }