Add DeadEvent

A dead events wraps an event that was dispatched but not delivered to
any handler. The dead event is than dispatched to dedicated handlers.

event-bus-core/src/test/java/dev/kske/eventbus/core/DeadTest.java

@@ -0,0 +1,37 @@
+package dev.kske.eventbus.core;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import org.junit.jupiter.api.*;
+
+/**
+ * Tests the dispatching of a dead event if an event could not be delivered.
+ *
+ * @author Kai S. K. Engelbart
+ * @since 1.1.0
+ */
+class DeadTest {
+
+	EventBus	bus;
+	String		event	= "This event has no handler";
+	boolean		deadEventHandled;
+
+	@BeforeEach
+	void registerListener() {
+		bus = new EventBus();
+		bus.registerListener(this);
+	}
+
+	@Test
+	void testDeadEvent() {
+		bus.dispatch(event);
+		assertTrue(deadEventHandled);
+	}
+
+	@Event
+	void onDeadEvent(DeadEvent deadEvent) {
+		assertEquals(bus, deadEvent.getEventBus());
+		assertEquals(event, deadEvent.getEvent());
+		deadEventHandled = true;
+	}
+}