1 files changed, 165 insertions, 0 deletions
diff --git a/undo/09-test-undo.js b/undo/09-test-undo.js
new file mode 100644
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+++ b/undo/09-test-undo.js
@@ -0,0 +1,165 @@
+var assert = require("assert")
+var UndoStack = require("./undo.js")
+UndoStack.debug = false
+
+describe('undo', function(){
+  
+  var state = "zero"
+  
+  describe('#register()', function(){
+  
+    UndoStack.register({
+      type: "demo",
+      undo: function(myState){
+        state = myState
+      },
+      redo: function(myState){
+        state = myState
+      },
+    })
+
+    it('registers undoable actions', function(){
+      assert( UndoStack.types.hasOwnProperty("demo") )
+    })
+  })
+  
+  describe('#push()', function(){
+    
+    it('starts empty', function(){
+      assert.equal(0, UndoStack.stack.length)
+      assert.equal(-1, UndoStack.pointer)
+    })
+    
+    it('pushes some actions', function(){
+
+      UndoStack.push({
+        type: "demo",
+        undo: state,
+        redo: "one"
+      })
+      state = "one"
+
+      UndoStack.push({
+        type: "demo",
+        undo: state,
+        redo: "two"
+      })
+      state = "two"
+
+      UndoStack.push({
+        type: "demo",
+        undo: state,
+        redo: "three"
+      })
+      state = "three"
+    
+      assert.equal(3, UndoStack.stack.length)
+      assert.equal(2, UndoStack.pointer)
+    })
+  })
+  
+  describe('#undo()', function(){
+  
+    it('retrieves old state', function(){
+      assert.equal("three", state)
+      UndoStack.undo()
+      assert.equal("two", state)
+      assert.equal(1, UndoStack.pointer)
+    })
+    
+    it('can only undo so far', function(){
+      var canUndo
+
+      canUndo = UndoStack.undo()
+      assert.equal("one", state)
+      assert.equal(0, UndoStack.pointer)
+      assert.equal(true, canUndo)
+
+      canUndo = UndoStack.undo()
+      assert.equal("zero", state)
+      assert.equal(-1, UndoStack.pointer)
+      assert.equal(false, canUndo)
+      
+      canUndo = UndoStack.undo()
+      assert.equal("zero", state)
+      assert.equal(-1, UndoStack.pointer)
+      assert.equal(false, canUndo)
+    })
+  
+  })
+
+  describe('#redo()', function(){
+
+    it('reassigns new state', function(){
+      UndoStack.redo()
+      assert.equal("one", state)
+    })
+    
+    it('can only redo so far', function(){
+      var canRedo
+      
+      canRedo = UndoStack.redo()
+      assert.equal("two", state)
+      assert.equal(true, canRedo)
+
+      canRedo = UndoStack.redo()
+      assert.equal("three", state)
+      assert.equal(false, canRedo)
+
+      canRedo = UndoStack.redo()
+      assert.equal("three", state)
+      assert.equal(false, canRedo)
+    })
+
+    it('clobbers old state if we undo then do something else', function(){
+      UndoStack.undo()
+      assert.equal("two", state)
+      assert.equal(1, UndoStack.pointer)
+
+      UndoStack.undo()
+      assert.equal("one", state)
+      assert.equal(0, UndoStack.pointer)
+      assert.equal(3, UndoStack.stack.length)
+
+      UndoStack.push({
+        type: "demo",
+        undo: state,
+        redo: "four"
+      })
+      state = "four"
+
+      assert.equal(1, UndoStack.pointer)
+      assert.equal(2, UndoStack.stack.length)
+
+      UndoStack.undo()
+      assert.equal("one", state)
+      assert.equal(0, UndoStack.pointer)
+      assert.equal(2, UndoStack.stack.length)
+
+      UndoStack.redo()
+      assert.equal("four", state)
+      assert.equal(1, UndoStack.pointer)
+      assert.equal(2, UndoStack.stack.length)
+    })
+  })
+  
+})
+
+// 1) push action
+// 2) push action
+// 3) push action
+// undo 3
+// undo 2
+// undo 1
+// undo * can't undo anymore
+// redo 1
+// redo 2
+// redo 3
+// redo * can't redo anymore
+// undo 3
+// 4) push action (clobbers action 3)
+// undo 4
+// undo 2
+// redo 2
+// redo 4
+