src/main/java/Inventory/Inventory.java

@@ -1,6 +1,7 @@
 package Inventory;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 
 public class Inventory {
@@ -10,8 +11,8 @@ public class Inventory {
         items = new ArrayList<>();
     }
 
-    List<String> getItems() {
-        return items;
+    public List<String> getItems() {
+        return Collections.unmodifiableList(items);
     }
 
     public void addItem(String item) {

src/test/java/PlayerTest.java

@@ -7,6 +7,8 @@ import Entity.Player;
 import org.junit.jupiter.api.Test;
 import Job.Wizard;
 
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.hasItem;
 import static org.junit.jupiter.api.Assertions.*;
 
 class PlayerTest {
@@ -55,7 +57,7 @@ class PlayerTest {
         var p = new Player("John");
         p.learnJob(new Miner());
         p.performAction(new DigAction());
-        assertTrue(p.getInventory().containsItem("Stone"));
+        assertThat(p.getInventory().getItems(), hasItem("Stone"));
     }
 
     @Test