From d8b40e4240fb7f8c62fcd60c567ab386024741d3 Mon Sep 17 00:00:00 2001
From: Elizabeth Hunt <me@liz.coffee>
Date: Sat, 31 Jan 2026 13:08:16 -0800
Subject: A sokoban inspired grid push demo

---
 .../src/test/java/coffee/liz/ecs/DAGWorldTest.java | 45 ++++++++++++++++++++++
 1 file changed, 45 insertions(+)

(limited to 'core/src/test/java/coffee')

diff --git a/core/src/test/java/coffee/liz/ecs/DAGWorldTest.java b/core/src/test/java/coffee/liz/ecs/DAGWorldTest.java
index 2f948d0..a656d28 100644
--- a/core/src/test/java/coffee/liz/ecs/DAGWorldTest.java
+++ b/core/src/test/java/coffee/liz/ecs/DAGWorldTest.java
@@ -79,6 +79,24 @@ final class DAGWorldTest {
 		assertTrue(world.query(Set.of(PositionComponent.class)).isEmpty());
 	}
 
+	@Test
+	public void queryFindsComponentsAddedByEarlierSystemInSameTick() {
+		final List<Set<Entity>> queryResults = new CopyOnWriteArrayList<>();
+
+		final Map<Class<? extends System<String>>, System<String>> systems = new LinkedHashMap<>();
+		systems.put(ComponentAdderSystem.class, new ComponentAdderSystem());
+		systems.put(ComponentReaderSystem.class, new ComponentReaderSystem(queryResults));
+		final DAGWorld<String> world = new DAGWorld<>(systems);
+
+		final Entity entity = world.createEntity();
+		entity.add(new PositionComponent());
+
+		world.update("state", Duration.ZERO);
+
+		assertEquals(1, queryResults.size());
+		assertEquals(Set.of(entity), queryResults.getFirst());
+	}
+
 	@Test
 	public void circularDependencyDetectionThrowsIllegalStateException() {
 		final Map<Class<? extends System<String>>, System<String>> systems = new LinkedHashMap<>();
@@ -161,4 +179,31 @@ final class DAGWorldTest {
 		public void update(final World<String> world, final String state, final Duration duration) {
 		}
 	}
+
+	private static final class ComponentAdderSystem implements System<String> {
+		@Override
+		public Collection<Class<? extends System<String>>> getDependencies() {
+			return List.of();
+		}
+
+		@Override
+		public void update(final World<String> world, final String state, final Duration duration) {
+			world.query(Set.of(PositionComponent.class)).forEach(e -> e.add(new VelocityComponent()));
+		}
+	}
+
+	@RequiredArgsConstructor
+	private static final class ComponentReaderSystem implements System<String> {
+		private final List<Set<Entity>> queryResults;
+
+		@Override
+		public Collection<Class<? extends System<String>>> getDependencies() {
+			return Set.of(ComponentAdderSystem.class);
+		}
+
+		@Override
+		public void update(final World<String> world, final String state, final Duration duration) {
+			queryResults.add(world.query(Set.of(VelocityComponent.class, PositionComponent.class)));
+		}
+	}
 }
-- 
cgit v1.2.3-70-g09d2