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Duplicate file collection for non-pattern matching file #2679
Description
When py.test is executed with file_or_dir arguments for:
- a directory and
- a file that
- is in the directory but
- does not match the configured Python test module pattern (e.g.,
test_*.py),
the file will be collected twice.
I believe this is because the file in question is considered for collection twice (once as a member of an explicitly-requested directory and again as an explicitly-requested file) and matches Session#isinitpath both times, thus being collected twice.
This is similar to #1187, except that the file would not ordinarily be collected as a member of the directory, since it does not match the Python test module pattern. As such, this is not a case of explicitly requesting collection of the same file_or_dir twice.
Example
Setup
$ python --version
Python 2.7.13
$ pip list
pip (9.0.1)
py (1.4.34)
pytest (3.2.1)
setuptools (28.8.0)
$ tree
.
└── tests
├── _test_three.py
├── _test_two.py
└── test_one.py
Scenario A: Default test collection
$ py.test --collect-only
===================================== test session starts =====================================
platform darwin -- Python 2.7.13, pytest-3.2.1, py-1.4.34, pluggy-0.4.0
rootdir: $HOME/src/pytest-duplicate-collection, inifile:
collected 1 item
<Module 'tests/test_one.py'>
<Function 'test_one'>
================================ no tests ran in 0.01 seconds =================================
Scenario B: Explicit directory test collection
$ py.test --collect-only tests
===================================== test session starts =====================================
platform darwin -- Python 2.7.13, pytest-3.2.1, py-1.4.34, pluggy-0.4.0
rootdir: $HOME/src/pytest-duplicate-collection, inifile:
collected 1 item
<Module 'tests/test_one.py'>
<Function 'test_one'>
================================ no tests ran in 0.01 seconds =================================
Scenario C: Explicit non-matching file test collection
$ py.test --collect-only tests/_test_two.py
===================================== test session starts =====================================
platform darwin -- Python 2.7.13, pytest-3.2.1, py-1.4.34, pluggy-0.4.0
rootdir: $HOME/src/pytest-duplicate-collection, inifile:
collected 1 item
<Module 'tests/_test_two.py'>
<Function 'test_two'>
================================ no tests ran in 0.00 seconds =================================
Scenario D: Explicit directory and non-matching file test collection
$ py.test --collect-only tests tests/_test_two.py
===================================== test session starts =====================================
platform darwin -- Python 2.7.13, pytest-3.2.1, py-1.4.34, pluggy-0.4.0
rootdir: $HOME/src/pytest-duplicate-collection, inifile:
collected 3 items
<Module 'tests/_test_two.py'>
<Function 'test_two'>
<Module 'tests/test_one.py'>
<Function 'test_one'>
<Module 'tests/_test_two.py'>
<Function 'test_two'>
================================ no tests ran in 0.01 seconds =================================
Activity
nicoddemus commentedon Aug 15, 2017
@elliterate thanks for the report and the well detailed reproducer, we appreciate it. 👍
elliterate commentedon Oct 6, 2017
I don't understand how you reached that conclusion. Yes, this is what the code does, but that doesn't mean its behavior is by design. (If that were true, then there would be no such thing as a bug in software; everything would by definition be a feature, since that is how the code works.)
In #1187, the argument was made that if
py.test Acauses test set {X} to be executed, it would be reasonable to infer thatpy.test A Awould cause test set {X} + {X} to be executed. That is, if you request the collection of a path twice, it will collect all of the matching tests twice. I don't necessarily agree that it's a desirable behavior, but I can buy the argument that people might infer it.In this case, however, while
py.test Acauses test set {X} to be executed andpy.test Bcauses test set {Y} to be executed,py.test A Bcauses test set {X + Y} + {Y} to be executed. In other words, the request to collect path B is altering the collection of path A. I see no reason for anyone to infer or desire this behavior and I believe that makes this a completely difference scenario from #1187.Zac-HD commentedon Jul 21, 2026
Closing as resolved: fixed by #13704 (closing #12083), which made overlapping collection arguments resolve to their common prefix. Verified with this issue's reproducer on current
main:pytest --collect-only tests tests/_test_two.pycollects 1 item, with no duplication and no pattern-bypassing collection.