bpo-44282: Fix occasional test_incremental_editing failures on buildbots (GH-26491)

Signed-off-by: Tal Einat <532281+taleinat@users.noreply.github.com>

Lib/idlelib/idle_test/tkinter_testing_utils.py

@@ -2,7 +2,7 @@
 import functools
 
 
-def run_in_tk_mainloop(test_method):
+def run_in_tk_mainloop(delay=1):
     """Decorator for running a test method with a real Tk mainloop.
 
     This starts a Tk mainloop before running the test, and stops it
@@ -13,44 +13,50 @@ def run_in_tk_mainloop(test_method):
     using "yield" to allow the mainloop to process events and "after"
     callbacks, and then continue the test from that point.
 
+    The delay argument is passed into root.after(...) calls as the number
+    of ms to wait before passing execution back to the generator function.
+
     This also assumes that the test class has a .root attribute,
     which is a tkinter.Tk object.
 
     For example (from test_sidebar.py):
 
-    @run_test_with_tk_mainloop
+    @run_test_with_tk_mainloop()
     def test_single_empty_input(self):
         self.do_input('\n')
         yield
         self.assert_sidebar_lines_end_with(['>>>', '>>>'])
     """
-    @functools.wraps(test_method)
-    def new_test_method(self):
-        test_generator = test_method(self)
-        root = self.root
-        # Exceptions raised by self.assert...() need to be raised
-        # outside of the after() callback in order for the test
-        # harness to capture them.
-        exception = None
-        def after_callback():
-            nonlocal exception
-            try:
-                next(test_generator)
-            except StopIteration:
-                root.quit()
-            except Exception as exc:
-                exception = exc
-                root.quit()
-            else:
-                # Schedule the Tk mainloop to call this function again,
-                # using a robust method of ensuring that it gets a
-                # chance to process queued events before doing so.
-                # See: https://stackoverflow.com/q/18499082#comment65004099_38817470
-                root.after(1, root.after_idle, after_callback)
-        root.after(0, root.after_idle, after_callback)
-        root.mainloop()
+    def decorator(test_method):
+        @functools.wraps(test_method)
+        def new_test_method(self):
+            test_generator = test_method(self)
+            root = self.root
+            # Exceptions raised by self.assert...() need to be raised
+            # outside of the after() callback in order for the test
+            # harness to capture them.
+            exception = None
+            def after_callback():
+                nonlocal exception
+                try:
+                    next(test_generator)
+                except StopIteration:
+                    root.quit()
+                except Exception as exc:
+                    exception = exc
+                    root.quit()
+                else:
+                    # Schedule the Tk mainloop to call this function again,
+                    # using a robust method of ensuring that it gets a
+                    # chance to process queued events before doing so.
+                    # See: https://stackoverflow.com/q/18499082#comment65004099_38817470
+                    root.after(delay, root.after_idle, after_callback)
+            root.after(0, root.after_idle, after_callback)
+            root.mainloop()
 
-        if exception:
-            raise exception
+            if exception:
+                raise exception
 
-    return new_test_method
+        return new_test_method
+
+    return decorator