2 files changed, 46 insertions, 4 deletions
diff --git a/core/src/test/java/coffee/liz/ecs/DAGWorldTest.java b/core/src/test/java/coffee/liz/ecs/DAGWorldTest.java
index cf6cdad..4825e36 100644
--- a/core/src/test/java/coffee/liz/ecs/DAGWorldTest.java
+++ b/core/src/test/java/coffee/liz/ecs/DAGWorldTest.java
@@ -68,19 +68,31 @@ public class DAGWorldTest {
     }
 
     @Test
-    public void updateRefreshesComponentCacheAfterEntityMutations() {
+    public void cacheTracksComponentMutationsViaEntityEvents() {
         final DAGWorld<String> world = new DAGWorld<>();
         final Entity subject = world.createEntity();
 
-        world.update("state", 0);
         assertTrue(world.resolve(Query.allOf(PositionComponent.class)).isEmpty());
 
         subject.add(new PositionComponent());
-        world.update("state", 0);
         assertEquals(1, world.resolve(Query.allOf(PositionComponent.class)).size());
 
         subject.remove(PositionComponent.class);
-        world.update("state", 0);
+        assertTrue(world.resolve(Query.allOf(PositionComponent.class)).isEmpty());
+    }
+
+    @Test
+    public void removedEntityNoLongerMutatesWorldCache() {
+        final DAGWorld<String> world = new DAGWorld<>();
+        final Entity subject = world.createEntity();
+
+        subject.add(new PositionComponent());
+        assertEquals(Set.of(subject), world.resolve(Query.allOf(PositionComponent.class)));
+
+        world.removeEntity(subject);
+        subject.remove(PositionComponent.class);
+        subject.add(new PositionComponent());
+
         assertTrue(world.resolve(Query.allOf(PositionComponent.class)).isEmpty());
     }
 
diff --git a/core/src/test/java/coffee/liz/ecs/model/EntityTest.java b/core/src/test/java/coffee/liz/ecs/model/EntityTest.java
index a8fd1e3..bb17296 100644
--- a/core/src/test/java/coffee/liz/ecs/model/EntityTest.java
+++ b/core/src/test/java/coffee/liz/ecs/model/EntityTest.java
@@ -6,6 +6,11 @@ import static org.junit.jupiter.api.Assertions.assertSame;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
+import coffee.liz.ecs.events.ComponentAdded;
+import coffee.liz.ecs.events.ComponentRemoved;
+import coffee.liz.ecs.events.EntityEvent;
+import coffee.liz.ecs.events.Hook;
+
 import lombok.RequiredArgsConstructor;
 
 import org.junit.jupiter.api.Test;
@@ -15,6 +20,7 @@ import org.junit.jupiter.params.provider.MethodSource;
 
 import java.util.Collection;
 import java.util.List;
+import java.util.concurrent.atomic.AtomicInteger;
 import java.util.stream.Stream;
 
 final class EntityTest {
@@ -75,6 +81,30 @@ final class EntityTest {
         assertTrue(entity.componentTypes().isEmpty());
     }
 
+    @Test
+    public void subscribeReceivesEmittedEvents() {
+        final Entity entity = Entity.builder().id(51).build();
+        final AtomicInteger addedCount = new AtomicInteger(0);
+        final AtomicInteger removedCount = new AtomicInteger(0);
+
+        final Hook<EntityEvent> hook = entity.subscribe(event -> {
+            if (event instanceof ComponentAdded) {
+                addedCount.incrementAndGet();
+            }
+            if (event instanceof ComponentRemoved) {
+                removedCount.incrementAndGet();
+            }
+        });
+
+        entity.add(new AlphaComponent("a"));
+        entity.remove(AlphaComponent.class);
+
+        assertEquals(1, addedCount.get());
+        assertEquals(1, removedCount.get());
+
+        entity.unsubscribe(hook);
+    }
+
     private record AlphaComponent(String name) implements Component {
     }