Skip page check in promise for Tab Nav in bok-choy suite

common/test/acceptance/pages/lms/tab_nav.py

@@ -36,15 +36,10 @@ class TabNavPage(PageObject):
     def is_on_tab(self, tab_name):
         """
         Return a boolean indicating whether the current tab is `tab_name`.
+        Because this is a public method, it checks that we're on the right page
+        before accessing the DOM.
         """
-        current_tab_list = self.css_text('ol.course-tabs>li>a.active')
-
-        if len(current_tab_list) == 0:
-            self.warning("Could not find current tab")
-            return False
-
-        else:
-            return (current_tab_list[0].strip().split('\n')[0] == tab_name)
+        return self._is_on_tab(tab_name)
 
     def _tab_css(self, tab_name):
         """
@@ -73,11 +68,28 @@ class TabNavPage(PageObject):
 
         return fulfill(Promise(_check_func, "Get all tab names"))
 
+    def _is_on_tab(self, tab_name):
+        """
+        Return a boolean indicating whether the current tab is `tab_name`.
+        This is a private method, so it does NOT enforce the page check,
+        which is what we want when we're polling the DOM in a promise.
+        """
+        current_tab_list = self.css_text('ol.course-tabs>li>a.active')
+
+        if len(current_tab_list) == 0:
+            self.warning("Could not find current tab")
+            return False
+
+        else:
+            return (current_tab_list[0].strip().split('\n')[0] == tab_name)
+
+
     def _is_on_tab_promise(self, tab_name):
         """
         Return a `Promise` that the user is on the tab `tab_name`.
         """
+        # Use the private version of _is_on_tab to skip the page check
         return EmptyPromise(
-            lambda: self.is_on_tab(tab_name),
+            lambda: self._is_on_tab(tab_name),
             "{0} is the current tab".format(tab_name)
         )