Test Added

src/test/java/seedu/address/flashcard/CardIdTest.java

@@ -0,0 +1,21 @@
+package seedu.address.flashcard;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class CardIdTest {
+
+    private CardId id1 = new CardId();
+    private CardId id2 = new CardId();
+    private CardId id3 = new CardId();
+    private CardId id4 = new CardId();
+
+    @Test
+    public void generateIdTest() {
+        assertEquals(0, id1.getIdentityNumber());
+        assertEquals(1, id2.getIdentityNumber());
+        assertEquals(2, id3.getIdentityNumber());
+        assertEquals(3, id4.getIdentityNumber());
+    }
+}