allow TAs to select the cohort of new posts.

TNL-153

common/static/coffee/spec/discussion/discussion_spec_helper.coffee

@@ -109,6 +109,7 @@ browser and pasting the output.  When that file changes, this one should be rege
     </div>
     <input type="submit" id="edit-post-submit" class="post-update" value="Update post">
     <a href="#" class="post-cancel">Cancel</a>
+  </div>
 </script>
 
 <script aria-hidden="true" type="text/template" id="thread-response-template">

common/static/coffee/spec/discussion/view/new_post_view_spec.coffee

@@ -226,19 +226,26 @@ describe "NewPostView", ->
           mode: "tab"
         )
 
-      expectCohortSelectorVisible = (view, visible) ->
-        expect(view.$(".js-group-select").is(":visible")).toEqual(visible)
+      checkVisibility = (view, expectedVisible) =>
+        view.render()
+        expect(view.$(".js-group-select").is(":visible")).toEqual(expectedVisible)
+        if expectedVisible
+          expect(view.$(".js-group-select").prop("disabled")).toEqual(false)
 
       it "is not visible to students", ->
-        @view.render()
-        expectCohortSelectorVisible(@view, false)
+        checkVisibility(@view, false)
+
+      it "allows TAs to see the cohort selector", ->
+        DiscussionSpecHelper.makeTA()
+        checkVisibility(@view, true)
 
-      it "allows moderators to select visibility", ->
+      it "allows moderators to see the cohort selector", ->
         DiscussionSpecHelper.makeModerator()
-        @view.render()
-        expectCohortSelectorVisible(@view, true)
-        expect(@view.$(".js-group-select").prop("disabled")).toEqual(false)
+        checkVisibility(@view, true)
 
+      it "allows the user to make a cohort selection", ->
+        DiscussionSpecHelper.makeModerator()
+        @view.render()
         expectedGroupId = null
         DiscussionSpecHelper.makeAjaxSpy(
           (params) -> expect(params.data.group_id).toEqual(expectedGroupId)