diff --git a/src/js/service/HistoryService.js b/src/js/service/HistoryService.js
index 973f428..62b84e3 100644
--- a/src/js/service/HistoryService.js
+++ b/src/js/service/HistoryService.js
@@ -1,12 +1,10 @@
 (function () {
   var ns = $.namespace('pskl.service');
 
-  var SNAPSHOT_PERIOD = 50;
-  var LOAD_STATE_INTERVAL = 50;
-
-  ns.HistoryService = function (piskelController, shortcutService) {
-    this.piskelController = piskelController || pskl.app.piskelController;
-    this.shortcutService = shortcutService || pskl.app.shortcutService;
+  ns.HistoryService = function (piskelController, shortcutService, deserializer) {
+    this.$piskelController = piskelController || pskl.app.piskelController;
+    this.$shortcutService = shortcutService || pskl.app.shortcutService;
+    this.$deserializer = deserializer || pskl.utils.serialization.Deserializer;
 
     this.stateQueue = [];
     this.currentIndex = -1;
@@ -18,6 +16,8 @@
 
   ns.HistoryService.SNAPSHOT = 'SNAPSHOT';
   ns.HistoryService.REPLAY = 'REPLAY';
+  ns.HistoryService.SNAPSHOT_PERIOD = 50;
+  ns.HistoryService.LOAD_STATE_INTERVAL = 50;
   /**
    * This event alters the state (frames, layers) of the piskel. The event is triggered before the execution of associated command.
    * Don't store snapshots for such events.
@@ -27,8 +27,8 @@
   ns.HistoryService.prototype.init = function () {
     $.subscribe(Events.PISKEL_SAVE_STATE, this.onSaveStateEvent.bind(this));
 
-    this.shortcutService.addShortcut('ctrl+Z', this.undo.bind(this));
-    this.shortcutService.addShortcut('ctrl+Y', this.redo.bind(this));
+    this.$shortcutService.addShortcut('ctrl+Z', this.undo.bind(this));
+    this.$shortcutService.addShortcut('ctrl+Y', this.redo.bind(this));
 
     this.saveState({
       type : ns.HistoryService.SNAPSHOT
@@ -45,17 +45,17 @@
 
     var state = {
       action : stateInfo,
-      frameIndex : this.piskelController.currentFrameIndex,
-      layerIndex : this.piskelController.currentLayerIndex
+      frameIndex : this.$piskelController.currentFrameIndex,
+      layerIndex : this.$piskelController.currentLayerIndex
     };
 
     var isSnapshot = stateInfo.type === ns.HistoryService.SNAPSHOT;
     var isNoSnapshot = stateInfo.type === ns.HistoryService.REPLAY_NO_SNAPSHOT;
-    var isAtAutoSnapshotInterval = this.currentIndex % SNAPSHOT_PERIOD === 0 || this.saveNextAsSnapshot;
+    var isAtAutoSnapshotInterval = this.currentIndex % ns.HistoryService.SNAPSHOT_PERIOD === 0 || this.saveNextAsSnapshot;
     if (isNoSnapshot && isAtAutoSnapshotInterval) {
       this.saveNextAsSnapshot = true;
     } else if (isSnapshot || isAtAutoSnapshotInterval) {
-      state.piskel = this.piskelController.serialize(true);
+      state.piskel = this.$piskelController.serialize(true);
       this.saveNextAsSnapshot = false;
     }
 
@@ -71,7 +71,7 @@
   };
 
   ns.HistoryService.prototype.isLoadStateAllowed_ = function (index) {
-    var timeOk = (Date.now() - this.lastLoadState) > LOAD_STATE_INTERVAL;
+    var timeOk = (Date.now() - this.lastLoadState) > ns.HistoryService.LOAD_STATE_INTERVAL;
     var indexInRange = index >= 0 && index < this.stateQueue.length;
     return timeOk && indexInRange;
   };
@@ -94,7 +94,7 @@
         }
         var serializedPiskel = this.getSnapshotFromState_(snapshotIndex);
         var onPiskelLoadedCb = this.onPiskelLoaded_.bind(this, index, snapshotIndex);
-        pskl.utils.serialization.Deserializer.deserialize(serializedPiskel, onPiskelLoadedCb);
+        this.$deserializer.deserialize(serializedPiskel, onPiskelLoadedCb);
       }
     } catch (e) {
       window.console.error("[CRITICAL ERROR] : Unable to load a history state.");
@@ -126,8 +126,8 @@
 
   ns.HistoryService.prototype.onPiskelLoaded_ = function (index, snapshotIndex, piskel) {
     var originalSize = this.getPiskelSize_();
-    piskel.setDescriptor(this.piskelController.piskel.getDescriptor());
-    this.piskelController.setPiskel(piskel);
+    piskel.setDescriptor(this.$piskelController.piskel.getDescriptor());
+    this.$piskelController.setPiskel(piskel);
 
     for (var i = snapshotIndex + 1 ; i <= index ; i++) {
       var state = this.stateQueue[i];
@@ -135,6 +135,7 @@
       this.replayState(state);
     }
 
+    // Should only do this when going backwards
     var lastState = this.stateQueue[index+1];
     if (lastState) {
       this.setupState(lastState);
@@ -148,18 +149,18 @@
   };
 
   ns.HistoryService.prototype.getPiskelSize_ = function () {
-    return this.piskelController.getWidth() + 'x' + this.piskelController.getHeight();
+    return this.$piskelController.getWidth() + 'x' + this.$piskelController.getHeight();
   };
 
   ns.HistoryService.prototype.setupState = function (state) {
-    this.piskelController.setCurrentFrameIndex(state.frameIndex);
-    this.piskelController.setCurrentLayerIndex(state.layerIndex);
+    this.$piskelController.setCurrentFrameIndex(state.frameIndex);
+    this.$piskelController.setCurrentLayerIndex(state.layerIndex);
   };
 
   ns.HistoryService.prototype.replayState = function (state) {
     var action = state.action;
     var type = action.type;
-    var layer = this.piskelController.getLayerAt(state.layerIndex);
+    var layer = this.$piskelController.getLayerAt(state.layerIndex);
     var frame = layer.getFrameAt(state.frameIndex);
     action.scope.replay(frame, action.replay);
   };
diff --git a/test/js/service/HistoryServiceTest.js b/test/js/service/HistoryServiceTest.js
index f201f41..15827bb 100644
--- a/test/js/service/HistoryServiceTest.js
+++ b/test/js/service/HistoryServiceTest.js
@@ -1,22 +1,86 @@
-describe("History Service suite", function() {
-  it("starts at -1", function() {
-    var mockPiskelController = {};
-    var mockShortcutService = {};
-    var historyService = new pskl.service.HistoryService(mockPiskelController, mockShortcutService);
-    expect(historyService.currentIndex).toBe(-1);
-  });
+var callFactory = function (method) {
+  return {
+    times : function (times) {
+      var results = [];
+      for (var i = 0 ; i < times ; i++) {
+        results.push(method());
+      }
+      return results;
+    },
+    once : function () {
+      return method();
+    }
+  };
+};
 
-  it("is at 0 after init", function() {
+describe("History Service suite", function() {
+  var SERIALIZED_PISKEL = 'serialized-piskel';
+  var historyService = null;
+
+  var getLastState = function () {
+    return historyService.stateQueue[historyService.currentIndex];
+  };
+
+  var createMockHistoryService = function () {
     var mockPiskelController = {
       serialize : function () {
-        return 'serialized-piskel';
+        return SERIALIZED_PISKEL;
       }
     };
     var mockShortcutService = {
       addShortcut : function () {}
     };
-    var historyService = new pskl.service.HistoryService(mockPiskelController, mockShortcutService);
+    return new pskl.service.HistoryService(mockPiskelController, mockShortcutService);
+  };
+
+  it("starts at -1", function() {
+    historyService = createMockHistoryService();
+    expect(historyService.currentIndex).toBe(-1);
+  });
+
+  it("is at 0 after init", function() {
+    historyService = createMockHistoryService();
     historyService.init();
     expect(historyService.currentIndex).toBe(0);
   });
+
+  var sendSaveEvents = function (type) {
+    return callFactory (function () {
+      $.publish(Events.PISKEL_SAVE_STATE, {
+        type : type,
+        scope : {},
+        replay : {}
+      });
+    });
+  };
+
+  it("stores a piskel snapshot after 5 SAVE", function () {
+    // BEFORE
+    var SNAPSHOT_PERIOD_BACKUP = pskl.service.HistoryService.SNAPSHOT_PERIOD;
+    pskl.service.HistoryService.SNAPSHOT_PERIOD = 5;
+
+    historyService = createMockHistoryService();
+    historyService.init();
+
+    sendSaveEvents(pskl.service.HistoryService.REPLAY).times(5);
+
+    expect(historyService.currentIndex).toBe(5);
+
+    expect(getLastState().piskel).toBe(SERIALIZED_PISKEL);
+
+    sendSaveEvents(pskl.service.HistoryService.REPLAY).times(4);
+
+    sendSaveEvents(pskl.service.HistoryService.REPLAY_NO_SNAPSHOT).once();
+    expect(getLastState().piskel).toBeUndefined();
+
+    sendSaveEvents(pskl.service.HistoryService.REPLAY_NO_SNAPSHOT).once();
+    expect(getLastState().piskel).toBeUndefined();
+
+    sendSaveEvents(pskl.service.HistoryService.REPLAY).once();
+    expect(getLastState().piskel).toBe(SERIALIZED_PISKEL);
+
+    // AFTER
+    pskl.service.HistoryService.SNAPSHOT_PERIOD = SNAPSHOT_PERIOD_BACKUP;
+
+  })
 });
\ No newline at end of file