Add tests

pom.xml

@@ -14,6 +14,15 @@
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     </properties>
 
+    <dependencies>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>4.13.1</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
     <build>
         <plugins>
             <plugin>

src/test/java/LibraryTest.java

@@ -0,0 +1,55 @@
+import edu.uastw.Book;
+import edu.uastw.Library;
+import edu.uastw.LibraryItem;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.lang.reflect.Field;
+import java.util.List;
+
+import static org.junit.Assert.*;
+
+public class LibraryTest {
+    private Library library;
+
+    @Before
+    public void setUp() {
+        library = Library.getInstance();
+    }
+
+    @After
+    public void tearDown() throws NoSuchFieldException, IllegalAccessException {
+        Field libraryItemsField = Library.class.getDeclaredField("libraryItems");
+        libraryItemsField.setAccessible(true);
+        List<LibraryItem> libraryItems = (List<LibraryItem>) libraryItemsField.get(library);
+        libraryItems.clear();
+    }
+    @Test
+    public void testAddItem() {
+        LibraryItem book = new Book("Test Book", "Test Author");
+        library.addLibraryItem(book);
+        assertTrue(library.iterator().hasNext());
+    }
+
+    @Test
+    public void testIterator() {
+        LibraryItem book = new Book("Test Book", "Test Author");
+        library.addLibraryItem(book);
+        assertTrue(library.iterator().hasNext());
+        assertEquals(book, library.iterator().next());
+    }
+
+    @Test
+    public void testBooksCapacity() {
+        LibraryItem book1 = new Book("Book 1", "Author 1");
+        LibraryItem book2 = new Book("Book 2", "Author 2");
+        LibraryItem book3 = new Book("Book 3", "Author 3");
+
+        library.addLibraryItem(book1);
+        library.addLibraryItem(book2);
+        library.addLibraryItem(book3);
+
+        assertEquals(3, library.getBooksCapacity());
+    }
+}