add new_window contextmanager for creating, switching, & waiting on new page

notebook/tests/selenium/utils.py

@@ -5,6 +5,8 @@ from selenium.webdriver.common.keys import Keys
 from selenium.webdriver.support.ui import WebDriverWait
 from selenium.webdriver.support import expected_conditions as EC
 
+from contextlib import contextmanager
+
 pjoin = os.path.join
 
 
@@ -127,3 +129,15 @@ class Notebook:
     def add_markdown_cell(self, index=-1, content="", render=True):
         self.add_cell(index, cell_type="markdown")
         self.edit_cell(index=index, content=content, render=render)
+@contextmanager
+def new_window(browser, selector=None):
+    """Creates new window, switches you to that window, waits for selector if set.
+    
+    """
+    initial_window_handles = browser.window_handles
+    yield
+    new_window_handle = next(window for window in browser.window_handles 
+                             if window not in initial_window_handles)
+    browser.switch_to_window(new_window_handle)
+    if selector is not None:
+        wait_for_selector(browser, selector)