diff --git a/spec-inbox/undo-manager-spec.coffee b/spec-inbox/undo-manager-spec.coffee
new file mode 100644
index 000000000..b2772d928
--- /dev/null
+++ b/spec-inbox/undo-manager-spec.coffee
@@ -0,0 +1,104 @@
+UndoManager = require "../src/flux/undo-manager"
+
+describe "UndoManager", ->
+  beforeEach ->
+    @undoManager = new UndoManager
+
+  it "Initializes empty", ->
+    expect(@undoManager._history.length).toBe 0
+    expect(@undoManager._position).toBe -1
+
+  it "can push a history item onto the stack", ->
+    @undoManager.immediatelySaveToHistory "A"
+    expect(@undoManager._history[0]).toBe "A"
+    expect(@undoManager._history.length).toBe 1
+    expect(@undoManager.current()).toBe "A"
+
+  it "updates the position", ->
+    @undoManager.immediatelySaveToHistory "A"
+    expect(@undoManager._position).toBe 0
+
+  describe "when undoing", ->
+    beforeEach ->
+      @undoManager.immediatelySaveToHistory "A"
+      @undoManager.immediatelySaveToHistory "AB"
+      @undoManager.immediatelySaveToHistory "ABC"
+
+    it "returns the last item on the stack", ->
+      expect(@undoManager.undo()).toBe "AB"
+
+    it "doesn't change the size of the stack", ->
+      @undoManager.undo()
+      expect(@undoManager._history.length).toBe 3
+
+    it "set the position properly", ->
+      @undoManager.undo()
+      expect(@undoManager._position).toBe 1
+
+    it "returns null when there's nothing to undo", ->
+      @undoManager.undo()
+      @undoManager.undo()
+      expect(@undoManager.undo()).toBe null
+
+  describe "when redoing", ->
+    beforeEach ->
+      @undoManager.immediatelySaveToHistory "X"
+      @undoManager.immediatelySaveToHistory "XY"
+      @undoManager.immediatelySaveToHistory "XYZ"
+
+    it "returns the last item on the stack", ->
+      @undoManager.undo()
+      expect(@undoManager.redo()).toBe "XYZ"
+
+    it "doesn't change the size of the stack", ->
+      @undoManager.undo()
+      @undoManager.redo()
+      expect(@undoManager._history.length).toBe 3
+
+    it "set the position properly", ->
+      @undoManager.undo()
+      @undoManager.redo()
+      expect(@undoManager._position).toBe 2
+
+    it "returns null when there's nothing to redo", ->
+      expect(@undoManager.redo()).toBe null
+
+  describe "when undoing and adding items", ->
+    beforeEach ->
+      @undoManager.immediatelySaveToHistory "1"
+      @undoManager.immediatelySaveToHistory "12"
+      @undoManager.immediatelySaveToHistory "123"
+      @undoManager.immediatelySaveToHistory "1234"
+      @undoManager.undo()
+      @undoManager.undo()
+      @undoManager.immediatelySaveToHistory "A"
+
+    it "correctly sets the history", ->
+      expect(@undoManager._history).toEqual ["1", "12", "A"]
+
+    it "correctly sets the length", ->
+      expect(@undoManager._history.length).toBe 3
+
+    it "puts the correct items on the stack", ->
+      @undoManager.undo()
+      expect(@undoManager.redo()).toBe "A"
+
+    it "sets the position correctly", ->
+      expect(@undoManager._position).toBe 2
+
+  describe "when the stack is full", ->
+    beforeEach ->
+      @undoManager._MAX_HISTORY_SIZE = 2
+      @undoManager.immediatelySaveToHistory "A"
+      @undoManager.immediatelySaveToHistory "AB"
+      @undoManager.immediatelySaveToHistory "ABC"
+      @undoManager.immediatelySaveToHistory "ABCD"
+
+    it "correctly sets the length", ->
+      expect(@undoManager._history.length).toBe 2
+
+    it "keeps the latest histories", ->
+      expect(@undoManager._history).toEqual ["ABC", "ABCD"]
+
+    it "updates the position", ->
+      expect(@undoManager._position).toBe 1