diff --git a/internal/entity/entity_test.go b/internal/entity/entity_test.go
new file mode 100644
index 0000000..b043b11
--- /dev/null
+++ b/internal/entity/entity_test.go
@@ -0,0 +1,40 @@
+package entity_test
+
+import (
+	"testing"
+
+	"github.com/CPunch/gopenfusion/internal/entity"
+)
+
+func TestChunkSliceDifference(t *testing.T) {
+	chunks := []*entity.Chunk{
+		entity.NewChunk(entity.MakeChunkPosition(0, 0)),
+		entity.NewChunk(entity.MakeChunkPosition(0, 1)),
+		entity.NewChunk(entity.MakeChunkPosition(1, 0)),
+		entity.NewChunk(entity.MakeChunkPosition(1, 1)),
+	}
+
+	c1 := []*entity.Chunk{
+		chunks[0],
+		chunks[1],
+		chunks[2],
+		chunks[3],
+	}
+
+	c2 := []*entity.Chunk{
+		chunks[0],
+		chunks[1],
+		chunks[2],
+	}
+
+	diff := entity.ChunkSliceDifference(c1, c2)
+	if len(diff) != 1 {
+		t.Logf("%+v", diff)
+		t.Error("expected 1 chunk in difference")
+	}
+
+	if diff[0] != chunks[3] {
+		t.Logf("%+v", diff)
+		t.Error("wrong difference")
+	}
+}