Add Save and Load Functions to SimService

lib/service/simulation_service.dart

@@ -9,9 +9,10 @@ class SimulationService {
   static final int DEFAULT_GRID_SIZE = 50;
 
   final EngineService _engine;
-  final Simulation _sim = Simulation(DEFAULT_GRID_SIZE, DEFAULT_GRID_SIZE);
+  final Simulation _sim;
 
-  SimulationService(this._engine) {
+  SimulationService(this._engine, [Simulation sim])
+      : this._sim = sim ?? Simulation(DEFAULT_GRID_SIZE, DEFAULT_GRID_SIZE) {
     _engine.simulation = _sim;
     _sim.addRandomPattern(amount: 15, dispersal: 5);
   }
@@ -36,4 +37,7 @@ class SimulationService {
   void toggleGrid() {
     _sim.renderEdges = !_sim.renderEdges;
   }
+
+  void save() => _sim.saveSnapshot();
+  void load() => _sim.loadSnapshot();
 }

test/service/simulation_service_test.dart

@@ -0,0 +1,23 @@
+import 'package:rules_of_living/service/engine_service.dart';
+import 'package:rules_of_living/service/simulation_service.dart';
+import 'package:rules_of_living/src/Simulation.dart';
+import 'package:test/test.dart';
+import 'package:mockito/mockito.dart';
+
+class MockSimulation extends Mock implements Simulation {}
+
+class MockEngineService extends Mock implements EngineService {}
+
+void main() {
+  SimulationService sut;
+  MockSimulation mockSim = MockSimulation();
+  setUp(() => sut = SimulationService(MockEngineService(), mockSim));
+  test("calling save calls through to Simulation.saveSnapshot", () {
+    sut.save();
+    verify(mockSim.saveSnapshot());
+  });
+  test("calling load calls through to Simulation.loadSnapshot", () {
+    sut.load();
+    verify(mockSim.loadSnapshot());
+  });
+}