When add to cart fails, retry every 3 seconds, with no limit of the number of retries

spec/javascripts/unit/darkswarm/services/cart_spec.js.coffee

@@ -3,6 +3,8 @@ describe 'Cart service', ->
   Variants = null
   variant = null
   order = null
+  $httpBackend = null
+  $timeout = null
 
   beforeEach ->
     module 'Darkswarm'
@@ -16,9 +18,11 @@ describe 'Cart service', ->
       ]
     }
     angular.module('Darkswarm').value('currentOrder', order)
-    inject ($injector)->
+    inject ($injector, _$httpBackend_, _$timeout_)->
       Variants =  $injector.get("Variants")
       Cart =  $injector.get("Cart")
+      $httpBackend = _$httpBackend_
+      $timeout = _$timeout_
 
   it "backreferences line items", ->
     expect(Cart.line_items[0].variant.line_item).toBe Cart.line_items[0]
@@ -44,6 +48,29 @@ describe 'Cart service', ->
     order.line_items[0].quantity = 2
     expect(Cart.total_item_count()).toEqual 2
 
+  describe "updating the cart", ->
+    data = {variants: {}}
+
+    it "marks the form as saved on success", ->
+      spyOn(Cart, 'saved')
+      $httpBackend.expectPOST("/orders/populate", data).respond 200, {}
+      Cart.update()
+      $httpBackend.flush()
+      expect(Cart.saved).toHaveBeenCalled()
+
+    it "retries the update on failure", ->
+      spyOn(Cart, 'scheduleRetry')
+      $httpBackend.expectPOST("/orders/populate", data).respond 404, {}
+      Cart.update()
+      $httpBackend.flush()
+      expect(Cart.scheduleRetry).toHaveBeenCalled()
+
+  it "schedules retries of updates", ->
+    spyOn(Cart, 'orderChanged')
+    Cart.scheduleRetry()
+    $timeout.flush()
+    expect(Cart.orderChanged).toHaveBeenCalled()
+
   describe "generating an extended variant name", ->
     it "returns the product name when it is the same as the variant name", ->
       variant = {product_name: 'product_name', name_to_display: 'product_name'}