adding spyOnConstructor

README.md

@@ -68,6 +68,31 @@ someSpy("correct","params");
 expect(window.globalsRock).toBe(true);
 ```
 
+# Spying on constructors
+
+jasmine-stealth adds a facility to spy on a constructor. That way, when your subject code
+that's under test instantiates a collaborator, you can access its methods as a collection of spies.
+
+Say we have a `view` that instantiates a `model`. Here's an example spec that uses `spyOnConstructor` to isolate the view from the model.
+
+``` coffee
+#source
+class window.View
+  serialize: ->
+    model: new Model().toJSON()
+class window.Model
+
+#specs
+describe "View", ->
+  describe "#serialize", ->
+    Given -> @modelSpies = spyOnConstructor(window, "Model", "toJSON")
+    Given -> @subject = new window.View()
+    Given -> @modelSpies.toJSON.andReturn("some json")
+    When -> @result = @subject.serialize()
+    Then -> expect(@result).toEqual
+      model: "some json"
+```
+
 # Custom matchers
 
 The problem:

spec/jasmine-stealth-spec.coffee

@@ -219,6 +219,44 @@ describe "jasmine-stealth", ->
       expect(save).toHaveBeenCalledWith(captor.capture())
       expect(captor.value.name).toBe("foo")
 
+  describe "window.spyOnConstructor", ->
+    describe "a simple class", ->
+      class window.Pizza
+        makeSlice: -> "nah"
+
+      context "spying on the constructor - string method arg", ->
+        Given -> @pizzaSpies = spyOnConstructor(window, "Pizza", "makeSlice")
+        When -> new Pizza("banz").makeSlice("lol")
+        Then -> expect(@pizzaSpies.constructor).toHaveBeenCalledWith("banz")
+        Then -> expect(@pizzaSpies.makeSlice).toHaveBeenCalledWith("lol")
+
+      context "spying on the constructor - array method arg", ->
+        Given -> @pizzaSpies = spyOnConstructor(window, "Pizza", ["makeSlice"])
+        When -> new Pizza("banz").makeSlice("lol")
+        Then -> expect(@pizzaSpies.constructor).toHaveBeenCalledWith("banz")
+        Then -> expect(@pizzaSpies.makeSlice).toHaveBeenCalledWith("lol")
+
+      context "normal operation", ->
+        Given -> @pizza = new Pizza
+        Then -> @pizza.makeSlice() == "nah"
+
+    describe "a collaboration", ->
+      class window.View
+        serialize: ->
+          model: new Model().toJSON()
+      class window.Model
+
+      context "stubbing the model's method", ->
+        Given -> @modelSpies = spyOnConstructor(window, "Model", "toJSON")
+        Given -> @subject = new window.View()
+        Given -> @modelSpies.toJSON.andReturn("some json")
+        When -> @result = @subject.serialize()
+        Then -> expect(@result).toEqual
+          model: "some json"
+
+
+
+
 
 
 

src/jasmine-stealth.coffee

@@ -7,9 +7,40 @@ root = this
 
 #private helpers
 
-isFunction = (thing) ->
-  Object::toString.call(thing) is "[object Function]"
+_ = (obj) ->
+  each: (iterator) ->
+    iterator(item) for item in obj
+  isFunction: ->
+    Object::toString.call(obj) is "[object Function]"
+  isString: ->
+    Object::toString.call(obj) is "[object String]"
 
+#spyOnConstructor
+
+root.spyOnConstructor = (owner, classToFake, methodsToSpy = []) ->
+  methodsToSpy = [methodsToSpy] if _(methodsToSpy).isString()
+
+  spies = constructor: jasmine.createSpy("#{classToFake}'s constructor")
+  fakeClass = class
+    constructor: -> spies.constructor.apply(@, arguments)
+
+  _(methodsToSpy).each (methodName) ->
+    spies[methodName] = jasmine.createSpy("#{classToFake}##{methodName}")
+    fakeClass.prototype[methodName] = -> spies[methodName].apply(@,arguments)
+
+  fake(owner, classToFake, fakeClass)
+  spies
+
+unfakes = []
+afterEach ->
+  _(unfakes).each (u) -> u()
+  unfakes = []
+
+fake = (owner, thingToFake, newThing) ->
+  originalThing = owner[thingToFake]
+  owner[thingToFake] = newThing
+  unfakes.push ->
+    owner[thingToFake] = originalThing
 
 #stub nomenclature
 
@@ -23,7 +54,7 @@ jasmine.createStubObj = (baseName, stubbings) ->
     for name of stubbings
       stubbing = stubbings[name]
       obj[name] = jasmine.createSpy(baseName + "." + name)
-      if isFunction(stubbing)
+      if _(stubbing).isFunction()
         obj[name].andCallFake stubbing
       else
         obj[name].andReturn stubbing