Add tests for ThreadController.isNew()

h/static/scripts/directive/test/thread-test.coffee

@@ -42,6 +42,25 @@ describe 'thread', ->
 
   describe 'controller', ->
 
+    it 'returns true from isNew() for a new annotation', ->
+      createDirective()
+
+      # When the user clicks to create a new annotation in the browser, we get
+      # a ThreadController with a container with a message (the annotation)
+      # with no id.
+      controller.container = {message: {}}
+
+      assert(controller.isNew())
+
+    it 'returns false from isNew() for an old annotation', ->
+      createDirective()
+
+      # When we create a ThreadController for an old annotation, the controller
+      # has a container with a message (the annotation) with an id.
+      controller.container = {message: {id: 123}}
+
+      assert(not controller.isNew())
+
     describe '#toggleCollapsed', ->
       count = null