Create some subroutines and test

src/game/rule/operation/operation_test.go

@@ -0,0 +1,13 @@
+package operation
+
+import (
+	"local/sandbox/cards/src/entity"
+	"testing"
+)
+
+func TestOperationInterface(t *testing.T) {
+	foo := func(*entity.Game, interface{}) int { return 0 }
+	var _ Int = foo
+	bar := func(*entity.Game, interface{}) bool { return false }
+	var _ Bool = bar
+}