Issue #18104: Add idlelib/idle_test/htest.py with a few sample tests to begin

consolidating and improving human-validated tests of Idle. Change other files
as needed to work with htest.  Running the module as __main__ runs all tests.

Lib/idlelib/EditorWindow.py

@@ -79,6 +79,8 @@ class HelpDialog(object):
         self.parent = None
 
 helpDialog = HelpDialog()  # singleton instance
+def _Help_dialog(parent):  # wrapper for htest
+    helpDialog.show_dialog(parent)
 
 
 class EditorWindow(object):
@@ -1064,7 +1066,7 @@ class EditorWindow(object):
         try:
             try:
                 mod = importlib.import_module('.' + name, package=__package__)
-            except ImportError:
+            except (ImportError, TypeError):
                 mod = importlib.import_module(name)
         except ImportError:
             print("\nFailed to import extension: ", name)
@@ -1700,19 +1702,21 @@ def fixwordbreaks(root):
     tk.call('set', 'tcl_nonwordchars', '[^a-zA-Z0-9_]')
 
 
-def test():
-    root = Tk()
+def _Editor_window(parent):
+    root = parent
     fixwordbreaks(root)
     root.withdraw()
     if sys.argv[1:]:
         filename = sys.argv[1]
     else:
         filename = None
+    macosxSupport.setupApp(root, None)
     edit = EditorWindow(root=root, filename=filename)
     edit.set_close_hook(root.quit)
     edit.text.bind("<<close-all-windows>>", edit.close_event)
-    root.mainloop()
-    root.destroy()
 
 if __name__ == '__main__':
-    test()
+    from idlelib.idle_test.htest import run
+    if len(sys.argv) <= 1:
+        run(_Help_dialog)
+    run(_Editor_window)