code: def test_wheel_event(self):
      # Fake widget class containing `yview` only.
      class _Widget:
          def __init__(widget, *expected):
              widget.expected = expected
  
          def yview(widget, *args):
              self.assertTupleEqual(widget.expected, args)
  
      # Fake event class
      class _Event:
          pass
  
      #        (type, delta, num, amount)
      tests = (
          (EventType.MouseWheel, 120, -1, -5),
          (EventType.MouseWheel, -120, -1, 5),
          (EventType.ButtonPress, -1, 4, -5),
          (EventType.ButtonPress, -1, 5, 5),
      )
  
      event = _Event()
      for ty, delta, num, amount in tests:
          event.type = ty
          event.delta = delta
          event.num = num
          res = tree.wheel_event(
              event, _Widget(SCROLL, amount, "units")
          )
          self.assertEqual(res, "break")
  
file_path: cpython/Lib/idlelib/idle_test/test_tree.py
imports: from idlelib import tree
  import unittest
  from test.support import requires
  from tkinter import Tk, EventType, SCROLL
label_desc: Use image node_id 1 for calling the TestScrollEvent obj's underlying member method code with example usage: obj.test_wheel_event() without return types