test: used ensureAdd

packages/pinball_components/test/src/components/spaceship_ramp/behavior/ramp_ball_ascending_contact_behavior_test.dart

@@ -99,12 +99,10 @@ void main() {
               spaceshipRamp,
               bloc: bloc,
             );
-            await opening.add(behavior);
+            await opening.ensureAdd(behavior);
 
             behavior.beginContact(ball, _MockContact());
 
-            await game.ready();
-
             verify(bloc.onAscendingBallEntered).called(1);
           },
         );
@@ -131,12 +129,10 @@ void main() {
               spaceshipRamp,
               bloc: bloc,
             );
-            await opening.add(behavior);
+            await opening.ensureAdd(behavior);
 
             behavior.beginContact(ball, _MockContact());
 
-            await game.ready();
-
             verifyNever(bloc.onAscendingBallEntered);
           },
         );