What's the problem this feature will solve?
Set comparisons that do not check for pure equality do not have nice assertion rewriting.
Examples:
# Set equality assertion message is nice! 👍
> assert {1, 2, 3} == {1, 2, 4}
E assert {1, 2, 3} == {1, 2, 4}
E Extra items in the left set:
E 3
E Extra items in the right set:
E 4
E Use -v to get more diff
# But others are not nice... 👎
# inequality
> assert {1, 2, 3} != {1, 2, 3}
E assert {1, 2, 3} != {1, 2, 3}
# proper subset
> assert {1, 2, 3} < {1, 2, 3}
E assert {1, 2, 3} < {1, 2, 3}
# proper superset
> assert {1, 2, 3} > {1, 2, 3}
E assert {1, 2, 3} > {1, 2, 3}
# superset
> assert {1, 2, 3} >= {1, 2, 4}
E assert {1, 2, 3} >= {1, 2, 4}
# subset
> assert {1, 2, 3} <= {1, 2, 4}
E assert {1, 2, 3} <= {1, 2, 4}
Describe the solution you'd like
When asserting sets are unequal, such as set_a <= set_b, the assertion text should be more intelligent only displaying the values that fail the check.
This might look like:
# inequality
> assert {1, 2, 3} != {1, 2, 3}
E assert {1, 2, 3} != {1, 2, 3}
E Sets are equal
# proper subset
> assert {1, 2, 3} < {1, 2, 3}
E assert {1, 2, 3} < {1, 2, 3}
E Sets are equal
# proper superset
> assert {1, 2, 3} > {1, 2, 3}
E assert {1, 2, 3} > {1, 2, 3}
E Sets are equal
# superset
> assert {1, 2, 3} >= {1, 2, 4}
E assert {1, 2, 3} >= {1, 2, 4}
E Extra items in the right set:
E 4
E Use -v to get more diff
# subset
> assert {1, 2, 3} <= {1, 2, 4}
E assert {1, 2, 3} <= {1, 2, 4}
E Extra items in the left set:
E 3
E Use -v to get more diff
Alternative Solutions
I'm not aware of any plugins or other tools that implement this, but I have creating my own using pytest_assertrepr_compare:
def pytest_assertrepr_compare(op, left, right):
if isinstance(left, set) and isinstance(right, set) and op == "!=":
return [
f"{left} {op} {right}", # N.B.: I know this isn't the _actual_ way to do this, but it's good enough for the example!
"Sets are equal"
]
if isinstance(left, set) and isinstance(right, set) and op == "<=":
extra = map(str, left - right)
return [
f"{left} {op} {right}",
"Extra items in left set:",
*extra,
]
if isinstance(left, set) and isinstance(right, set) and op == "<":
if left == right:
return [
f"{left} {op} {right}",
"Sets are equal"
]
extra = map(str, left - right)
return [
f"{left} {op} {right}",
"Extra items in left set:",
*extra,
]
if isinstance(left, set) and isinstance(right, set) and op == ">=":
extra = map(str, right - left)
return [
f"{left} {op} {right}",
"Extra items in right set:",
*extra,
]
if isinstance(left, set) and isinstance(right, set) and op == ">":
if left == right:
return [
f"{left} {op} {right}",
" Sets are equal",
]
extra = map(str, right - left)
return [
f"{left} {op} {right}",
"Extra items in right set:",
*extra,
]
We then get the following:
$ pytest pytest_set_assertion.py
======================================== test session starts =========================================
platform linux -- Python 3.9.13, pytest-7.2.0, pluggy-1.0.0
rootdir: /usr/local/google/home/dthor/dev/pytest_set_assertrepr
collected 8 items
pytest_set_assertion.py FFFFFFFF [100%]
============================================== FAILURES ==============================================
___________________________________________ test_equality ____________________________________________
def test_equality():
> assert {1, 2, 3} == {1, 2, 4, 5}
E assert {1, 2, 3} == {1, 2, 4, 5}
E Extra items in the left set:
E 3
E Extra items in the right set:
E 4
E 5
E Use -v to get more diff
pytest_set_assertion.py:2: AssertionError
__________________________________________ test_inequality ___________________________________________
def test_inequality():
> assert {1, 2, 3} != {1, 2, 3}
E assert {1, 2, 3} != {1, 2, 3}
E Sets are equal
pytest_set_assertion.py:6: AssertionError
____________________________________________ test_subset _____________________________________________
def test_subset():
> assert {1, 2, 3} <= {1, 2, 4}
E assert {1, 2, 3} <= {1, 2, 4}
E Extra items in left set:
E 3
pytest_set_assertion.py:10: AssertionError
_________________________________________ test_proper_subset _________________________________________
def test_proper_subset():
> assert {1, 2, 3} < {1, 2, 4}
E assert {1, 2, 3} < {1, 2, 4}
E Extra items in left set:
E 3
pytest_set_assertion.py:14: AssertionError
___________________________________ test_proper_subset_equal_sets ____________________________________
def test_proper_subset_equal_sets():
> assert {1, 2, 3} < {1, 2, 3}
E assert {1, 2, 3} < {1, 2, 3}
E Sets are equal
pytest_set_assertion.py:18: AssertionError
___________________________________________ test_superset ____________________________________________
def test_superset():
> assert {1, 2, 3} >= {1, 2, 4}
E assert {1, 2, 3} >= {1, 2, 4}
E Extra items in right set:
E 4
pytest_set_assertion.py:22: AssertionError
________________________________________ test_proper_superset ________________________________________
def test_proper_superset():
> assert {1, 2, 3} > {1, 2, 4}
E assert {1, 2, 3} > {1, 2, 4}
E Extra items in right set:
E 4
pytest_set_assertion.py:26: AssertionError
__________________________________ test_proper_superset_equal_sets ___________________________________
def test_proper_superset_equal_sets():
> assert {1, 2, 3} > {1, 2, 3}
E assert {1, 2, 3} > {1, 2, 3}
E Sets are equal
pytest_set_assertion.py:30: AssertionError
====================================== short test summary info =======================================
FAILED pytest_set_assertion.py::test_equality - assert {1, 2, 3} == {1, 2, 4, 5}
FAILED pytest_set_assertion.py::test_inequality - assert {1, 2, 3} != {1, 2, 3}
FAILED pytest_set_assertion.py::test_subset - assert {1, 2, 3} <= {1, 2, 4}
FAILED pytest_set_assertion.py::test_proper_subset - assert {1, 2, 3} < {1, 2, 4}
FAILED pytest_set_assertion.py::test_proper_subset_equal_sets - assert {1, 2, 3} < {1, 2, 3}
FAILED pytest_set_assertion.py::test_superset - assert {1, 2, 3} >= {1, 2, 4}
FAILED pytest_set_assertion.py::test_proper_superset - assert {1, 2, 3} > {1, 2, 4}
FAILED pytest_set_assertion.py::test_proper_superset_equal_sets - assert {1, 2, 3} > {1, 2, 3}
========================================= 8 failed in 0.06s ==========================================
Additional context
- Python 3.9.13 on Debian
- pytest 7.2.0
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