Test: Add unit tests for EventBus

src/test/java/ch/unibas/dmi/dbis/cs108/casono/server/network/events/EventBusTest.java

@@ -0,0 +1,49 @@
+package ch.unibas.dmi.dbis.cs108.casono.server.network.events;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicInteger;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+public class EventBusTest {
+    private EventBus eventBus;
+
+    @BeforeEach
+    void setUp() {
+        eventBus = new EventBus();
+    }
+
+    static class TestEvent implements Event {}
+
+    @Test
+    void singleSubscriberReceivesEvent() {
+        AtomicBoolean called = new AtomicBoolean(false);
+        eventBus.subscribe(TestEvent.class, e -> called.set(true));
+        eventBus.publish(new TestEvent());
+        assertTrue(called.get());
+    }
+
+    @Test
+    void multipleSubscribersReceiveEvent() {
+        AtomicInteger counter = new AtomicInteger(0);
+        eventBus.subscribe(TestEvent.class, e -> counter.incrementAndGet());
+        eventBus.subscribe(TestEvent.class, e -> counter.incrementAndGet());
+        eventBus.publish(new TestEvent());
+        assertEquals(2, counter.get());
+    }
+
+    @Test
+    void publishNullThrowsNpe() {
+        assertThrows(NullPointerException.class, () -> eventBus.publish((Event) null));
+    }
+
+    @Test
+    void subscribingToBaseEventDoesNotReceiveSubclass() {
+        AtomicBoolean called = new AtomicBoolean(false);
+        eventBus.subscribe(Event.class, e -> called.set(true));
+        eventBus.publish(new TestEvent());
+        assertFalse(called.get());
+    }
+}