I verified that the only failure is in test.test_tk:

FAIL: test_from (tkinter.test.test_tkinter.test_widgets.ScaleTest)
Traceback (most recent call last):
File "f:\dev\3x\lib\tkinter\test\test_tkinter\test_widgets.py", line 943, in test_from
self.checkFloatParam(widget, 'from', 100, 14.9, 15.1, conv=float_round)
File "f:\dev\3x\lib\tkinter\test\widget_tests.py", line 106, in checkFloatParam
self.checkParam(widget, name, value, conv=conv, **kwargs)
File "f:\dev\3x\lib\tkinter\test\widget_tests.py", line 63, in checkParam
self.assertEqual2(widget[name], expected, eq=eq)
File "f:\dev\3x\lib\tkinter\test\widget_tests.py", line 47, in assertEqual2
self.assertEqual(actual, expected, msg)
AssertionError: 14.9 != 15.0

The other 3 tkinter test files, test_idle, and test_turtle run OK.

The reason is that on Windows, tkinter.Scale['from'] was 'fixed' to match the behavior of tkinter.ttk.Scale.

In 3.9:

>>> import tkinter as tk
>>> r = tk.Tk()
>>> s = tk.Scale(r, from_=14.9)
>>> s.pack()
>>> s['from']
15.0
>>> from tkinter import ttk
>>> sk = ttk.Scale(r, from_=14.9)
>>> sk['from']
14.9

So test_from for tk and ttk respectively use float_round() = float(round()) and False.
self.checkFloatParam(widget, 'from', 100, 14.9, 15.1, conv=self.float_round)
self.checkFloatParam(widget, 'from', 100, 14.9, 15.1, conv=False)

In 8.6.10, s['from'] is 14.9 for tk.Scale also. So on Windows, conv should be False.

For tk.Scale, s['to'] is adjusted according to the s['from'], so if 'from' is left as the default 0.0, 14.9 and 15.1 are adjusted to 15.0. This is not true for ttk.Scale. Anyway, since test_to passes, we leave it alone.

When you're done making the requested changes, leave the comment: I have made the requested changes; please review again.

@serhiy-storchaka Looks like we're waiting on you - any further comment?

I verified that the only failure is in test.test_tk:

FAIL: test_from (tkinter.test.test_tkinter.test_widgets.ScaleTest)
Traceback (most recent call last):
File "f:\dev\3x\lib\tkinter\test\test_tkinter\test_widgets.py", line 943, in test_from
self.checkFloatParam(widget, 'from', 100, 14.9, 15.1, conv=float_round)
File "f:\dev\3x\lib\tkinter\test\widget_tests.py", line 106, in checkFloatParam
self.checkParam(widget, name, value, conv=conv, **kwargs)
File "f:\dev\3x\lib\tkinter\test\widget_tests.py", line 63, in checkParam
self.assertEqual2(widget[name], expected, eq=eq)
File "f:\dev\3x\lib\tkinter\test\widget_tests.py", line 47, in assertEqual2
self.assertEqual(actual, expected, msg)
AssertionError: 14.9 != 15.0

The other 3 tkinter test files, test_idle, and test_turtle run OK.

The reason is that on Windows, tkinter.Scale['from'] was 'fixed' to match the behavior of tkinter.ttk.Scale.

In 3.9:

>>> import tkinter as tk
>>> r = tk.Tk()
>>> s = tk.Scale(r, from_=14.9)
>>> s.pack()
>>> s['from']
15.0
>>> from tkinter import ttk
>>> sk = ttk.Scale(r, from_=14.9)
>>> sk['from']
14.9

So test_from for tk and ttk respectively use float_round() = float(round()) and False.
self.checkFloatParam(widget, 'from', 100, 14.9, 15.1, conv=self.float_round)
self.checkFloatParam(widget, 'from', 100, 14.9, 15.1, conv=False)

In 8.6.10, s['from'] is 14.9 for tk.Scale also. So on Windows, conv should be False.

For tk.Scale, s['to'] is adjusted according to the s['from'], so if 'from' is left as the default 0.0, 14.9 and 15.1 are adjusted to 15.0. This is not true for ttk.Scale. Anyway, since test_to passes, we leave it alone.

s[''resolution'] = 0.1
s['from_'] = 15.9
s['from_']
15.900000000000002
default, s[''resolution']=1, so 15.9 ==> 16, 15.5 ==> 16, 15.49 ==> 15