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Merged
merged 6 commits into from
May 1, 2017
Merged

bpo-30190: improved error msg for assertAlmostEqual(delta=...) #1331

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3b76f44
#30190 / unittest / assertAlmostEqual(delta=...) / error msg: show th…
giampaolo Apr 27, 2017
4f63471
safe_repr() diff
giampaolo Apr 28, 2017
dceb6a8
also show difference when passing 'places' argument
giampaolo Apr 28, 2017
6c55b42
refactoring
giampaolo Apr 28, 2017
e3a2706
Merge branch 'master' into 30190-unittest-improved-err-msg
giampaolo Apr 29, 2017
a30b8ea
update Misc/NEWS
giampaolo Apr 29, 2017
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35 changes: 21 additions & 14 deletions Lib/unittest/case.py
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Original file line number Diff line number Diff line change
Expand Up @@ -856,23 +856,28 @@ def assertAlmostEqual(self, first, second, places=None, msg=None,
if delta is not None and places is not None:
raise TypeError("specify delta or places not both")

diff = abs(first - second)
if delta is not None:
if abs(first - second) <= delta:
if diff <= delta:
return

standardMsg = '%s != %s within %s delta' % (safe_repr(first),
safe_repr(second),
safe_repr(delta))
standardMsg = '%s != %s within %s delta (%s difference)' % (
safe_repr(first),
safe_repr(second),
safe_repr(delta),
safe_repr(diff))
else:
if places is None:
places = 7

if round(abs(second-first), places) == 0:
if round(diff, places) == 0:
return

standardMsg = '%s != %s within %r places' % (safe_repr(first),
safe_repr(second),
places)
standardMsg = '%s != %s within %r places (%s difference)' % (
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What about assertNotAlmostEqual()?

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@giampaolo giampaolo Apr 28, 2017 •
edited
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Maybe I'm understanding the code wrong but assertNotAlmostEqual fails if the two numbers are almost equal and just "off" by a little. So in case of:

assertNotAlmostEqual(1.00000001, 1.0, places=7)

The failure will look like this:

AssertionError 1.00000001 == 1.0 within 7 places

...which is already enough. Makes sense?

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How this differs from the case when delta is specified?

Actually I don't know what is the use case for assertNotAlmostEqual(). It is not used in Python tests (except testing assertNotAlmostEqual() itself). I suggest to not change it at all.

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@giampaolo giampaolo Apr 28, 2017 •
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To my understanding delta is entirely about acceptable difference (hence it makes sense to show the absolute diff) whereas places is about decimal precision.
I'm also not sure what's the use case for assertNotAlmostEqual() but whoever uses it will find this:

self.assertNotAlmostEqual(5, 10, delta=15)

...produces:

AssertionError: 5 == 10 within 15 delta (5 difference)

...more readable than the current message
So in summary, for assertNotAlmostEqual, I'd be for showing the difference if delta is specified but not if places is specified.

safe_repr(first),
safe_repr(second),
places,
safe_repr(diff))
msg = self._formatMessage(msg, standardMsg)
raise self.failureException(msg)

Expand All @@ -890,16 +895,19 @@ def assertNotAlmostEqual(self, first, second, places=None, msg=None,
"""
if delta is not None and places is not None:
raise TypeError("specify delta or places not both")
diff = abs(first - second)
if delta is not None:
if not (first == second) and abs(first - second) > delta:
if not (first == second) and diff > delta:
return
standardMsg = '%s == %s within %s delta' % (safe_repr(first),
safe_repr(second),
safe_repr(delta))
standardMsg = '%s == %s within %s delta (%s difference)' % (
safe_repr(first),
safe_repr(second),
safe_repr(delta),
safe_repr(diff))
else:
if places is None:
places = 7
if not (first == second) and round(abs(second-first), places) != 0:
if not (first == second) and round(diff, places) != 0:
return
standardMsg = '%s == %s within %r places' % (safe_repr(first),
safe_repr(second),
Expand All @@ -908,7 +916,6 @@ def assertNotAlmostEqual(self, first, second, places=None, msg=None,
msg = self._formatMessage(msg, standardMsg)
raise self.failureException(msg)


def assertSequenceEqual(self, seq1, seq2, msg=None, seq_type=None):
"""An equality assertion for ordered sequences (like lists and tuples).

Expand Down
8 changes: 5 additions & 3 deletions Lib/unittest/test/test_assertions.py
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Original file line number Diff line number Diff line change
Expand Up @@ -223,9 +223,11 @@ def testNotEqual(self):
"^1 == 1 : oops$"])

def testAlmostEqual(self):
self.assertMessages('assertAlmostEqual', (1, 2),
["^1 != 2 within 7 places$", "^oops$",
"^1 != 2 within 7 places$", "^1 != 2 within 7 places : oops$"])
self.assertMessages(
'assertAlmostEqual', (1, 2),
["^1 != 2 within 7 places \(1 difference\)$", "^oops$",
"^1 != 2 within 7 places \(1 difference\)$",
"^1 != 2 within 7 places \(1 difference\) : oops$"])

def testNotAlmostEqual(self):
self.assertMessages('assertNotAlmostEqual', (1, 1),
Expand Down
6 changes: 5 additions & 1 deletion Misc/NEWS
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Original file line number Diff line number Diff line change
Expand Up @@ -10,7 +10,7 @@ What's New in Python 3.7.0 alpha 1?
Core and Builtins
-----------------

- bpo-12414: sys.getsizeof() on a code object now returns the sizes
- bpo-12414: sys.getsizeof() on a code object now returns the sizes
which includes the code struct and sizes of objects which it references.
Patch by Dong-hee Na.

Expand Down Expand Up @@ -317,6 +317,10 @@ Extension Modules
Library
-------

- bpo-30190: unittest's assertAlmostEqual and assertNotAlmostEqual provide a
better message in case of failure which includes the difference between
left and right arguments. (patch by Giampaolo Rodola')

- bpo-30101: Add support for curses.A_ITALIC.

- bpo-29822: inspect.isabstract() now works during __init_subclass__. Patch
Expand Down