Add grid changing function

lib/service/configuration_service.dart

@@ -1,3 +1,5 @@
+import 'dart:math';
+
 import 'package:rules_of_living/service/engine_service.dart';
 
 class ConfigurationService {
@@ -26,4 +28,10 @@ class ConfigurationService {
   void toggleGrid() {
     showGrid = !showGrid;
   }
-}
+
+  void setGridSize({int x, int y}) {
+    x = x ?? engineService.engine.gridSize.x;
+    y = y ?? engineService.engine.gridSize.y;
+    engineService.engine.gridSize = Point(x, y);
+  }
+}

test/service/configuration_service_test.dart

@@ -1,30 +1,46 @@
+import 'dart:math';
+
 import 'package:rules_of_living/src/Engine.dart';
 @TestOn('browser')
-
 import 'package:test/test.dart';
 import 'package:rules_of_living/service/configuration_service.dart';
 import 'package:rules_of_living/service/engine_service.dart';
 import 'package:mockito/mockito.dart';
 
 class MockEngine extends Mock implements Engine {}
-class MockEngineService extends Mock implements EngineService {
-  MockEngine _engine = MockEngine();
-  @override
-  Engine get engine => _engine;
-}
 
 void main() {
-  group("simulation speed", () {
-    ConfigurationService sut;
-    MockEngineService mes;
-    setUp(() {
-      mes = MockEngineService();
-      sut = ConfigurationService(mes);
-    });
+  ConfigurationService sut;
+  EngineService engineService;
+  MockEngine me;
+  setUp(() {
+    me = MockEngine();
+    engineService = EngineService();
+    engineService.getEngine(me);
+    sut = ConfigurationService(engineService);
+  });
 
+  group("simulation speed", () {
     test("speed changes propagate to engine", () {
       sut.simSpeed = 312;
-      verify(mes.engine.stepsPerSecond=312);
+      verify(me.stepsPerSecond = 312);
+    });
+  });
+
+  group("grid size", () {
+    test("grid changes are sent to engine", () {
+      sut.setGridSize(x: 512, y: 388);
+      verify(me.gridSize = Point(512, 388));
+    });
+    test("grid can be changed solely on x axis", () {
+      when(me.gridSize).thenReturn(Point(100, 100));
+      sut.setGridSize(x: 555);
+      verify(me.gridSize = Point(555, 100));
+    });
+    test("grid can be changed solely on y axis", () {
+      when(me.gridSize).thenReturn(Point(100, 100));
+      sut.setGridSize(y: 556);
+      verify(me.gridSize = Point(100, 556));
     });
   });
 }