Fix not using the selected Cash shop surprise

If you have multiple, it would always use the first one. Now it uses whichever you select (as expected).

src/test/java/testutil/Packets.java

@@ -2,11 +2,17 @@ package testutil;
 
 import io.netty.buffer.Unpooled;
 import net.packet.ByteBufInPacket;
+import net.packet.ByteBufOutPacket;
 import net.packet.InPacket;
+import net.packet.OutPacket;
+
+import java.util.function.Consumer;
 
 public class Packets {
 
-    public static InPacket emptyInPacket() {
-        return new ByteBufInPacket(Unpooled.buffer());
+    public static InPacket buildInPacket(Consumer<OutPacket> contentProvider) {
+        OutPacket builderInput = new ByteBufOutPacket();
+        contentProvider.accept(builderInput);
+        return new ByteBufInPacket(Unpooled.wrappedBuffer(builderInput.getBytes()));
     }
 }