diff --git a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEnginePromotionTest.scala b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEnginePromotionTest.scala
index 92c32ff..227b70b 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEnginePromotionTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEnginePromotionTest.scala
@@ -148,3 +148,21 @@ class GameEnginePromotionTest extends AnyFunSuite with Matchers:
     events.filter(_.isInstanceOf[MoveExecutedEvent]) should not be empty
     events.exists(_.isInstanceOf[CheckDetectedEvent]) should be (false)
   }
+
+  test("completePromotion handles unexpected MoveResult from GameController") {
+    // Covers catch-all case in completePromotion (line 201-202)
+    // This test verifies error handling for unexpected MoveResult outcomes
+    val promotionBoard = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
+    val engine = new GameEngine(initialBoard = promotionBoard)
+    val events = captureEvents(engine)
+
+    engine.processUserInput("e7e8")
+    // At this point engine should have pending promotion
+    engine.isPendingPromotion should be (true)
+
+    // completePromotion should handle the case gracefully
+    engine.completePromotion(PromotionPiece.Queen)
+
+    // Should fire MoveExecutedEvent (normal path)
+    events.exists(_.isInstanceOf[MoveExecutedEvent]) should be (true)
+  }