tests, docs: game engine fetch battle api

game/internal/router/router_helper_test.go

@@ -45,6 +45,13 @@ type dummyExecutor struct {
 	FetchOrderResult *order.UserGamesOrder
 	FetchOrderOK     bool
 	FetchOrderErr    error
+
+	// FetchBattle controls and observes calls to FetchBattle.
+	FetchBattleTurn   uint
+	FetchBattleID     uuid.UUID
+	FetchBattleResult *report.BattleReport
+	FetchBattleOK     bool
+	FetchBattleErr    error
 }
 
 func (e *dummyExecutor) ValidateOrder(actor string, cmd ...order.DecodableCommand) (*order.UserGamesOrder, error) {
@@ -69,7 +76,9 @@ func (e *dummyExecutor) FetchOrder(actor string, turn uint) (*order.UserGamesOrd
 }
 
 func (e *dummyExecutor) FetchBattle(turn uint, ID uuid.UUID) (*report.BattleReport, bool, error) {
-	return nil, false, nil
+	e.FetchBattleTurn = turn
+	e.FetchBattleID = ID
+	return e.FetchBattleResult, e.FetchBattleOK, e.FetchBattleErr
 }
 
 func (e *dummyExecutor) Execute(command ...handler.Command) error {