1"""Utilities for testing with Tkinter""" 2import functools 3 4 5def run_in_tk_mainloop(delay=1): 6 """Decorator for running a test method with a real Tk mainloop. 7 8 This starts a Tk mainloop before running the test, and stops it 9 at the end. This is faster and more robust than the common 10 alternative method of calling .update() and/or .update_idletasks(). 11 12 Test methods using this must be written as generator functions, 13 using "yield" to allow the mainloop to process events and "after" 14 callbacks, and then continue the test from that point. 15 16 The delay argument is passed into root.after(...) calls as the number 17 of ms to wait before passing execution back to the generator function. 18 19 This also assumes that the test class has a .root attribute, 20 which is a tkinter.Tk object. 21 22 For example (from test_sidebar.py): 23 24 @run_test_with_tk_mainloop() 25 def test_single_empty_input(self): 26 self.do_input('\n') 27 yield 28 self.assert_sidebar_lines_end_with(['>>>', '>>>']) 29 """ 30 def decorator(test_method): 31 @functools.wraps(test_method) 32 def new_test_method(self): 33 test_generator = test_method(self) 34 root = self.root 35 # Exceptions raised by self.assert...() need to be raised 36 # outside of the after() callback in order for the test 37 # harness to capture them. 38 exception = None 39 def after_callback(): 40 nonlocal exception 41 try: 42 next(test_generator) 43 except StopIteration: 44 root.quit() 45 except Exception as exc: 46 exception = exc 47 root.quit() 48 else: 49 # Schedule the Tk mainloop to call this function again, 50 # using a robust method of ensuring that it gets a 51 # chance to process queued events before doing so. 52 # See: https://stackoverflow.com/q/18499082#comment65004099_38817470 53 root.after(delay, root.after_idle, after_callback) 54 root.after(0, root.after_idle, after_callback) 55 root.mainloop() 56 57 if exception: 58 raise exception 59 60 return new_test_method 61 62 return decorator 63