Develop Reference

Identifying which test case is running on pytest-xdist processes

I'm executing python unit tests in parallel with pytest-forked (pytest -r sxX -n auto --cache-clear --max-worker-restart=4 --forked) and there is one test case which takes quite some time and which is running at the end while the other test case runners/CPU cores are idle (because presumably there's only this one test cases left to complete).
I'd like to know which test case that is (to maybe run it at the beginning or disable it). Note, this is not a matter of finding the longest running test case as that may not be the culprit. I'm explicitly looking for some way of knowing which test case is assigned to a pytest runner Python process. Calling ps shows something like python -u -c import sys; exec(eval(sys.stdin.readline())) (for as many CPU cores in the machine) which isn't particularly helpful.
Is there a way to set the name of the test case to the process and retrieve it with system tools such as ps? I'm running those test cases on Linux, in case that's relevant.

Since pytest-dist 2.4, there's a solution to showing which test case is running. It requires an additional package setproctitle.
Identifying workers from the system environment
New in version 2.4
If the setproctitle package is installed, pytest-xdist will use it to update the process title (command line) on its workers to show their current state. The titles used are [pytest-xdist running] file.py/node::id and [pytest-xdist idle], visible in standard tools like ps and top on Linux, Mac OS X and BSD systems. For Windows, please follow setproctitle’s pointer regarding the Process Explorer tool.
This is intended purely as an UX enhancement, e.g. to track down issues with long-running or CPU intensive tests. Errors in changing the title are ignored silently. Please try not to rely on the title format or title changes in external scripts.
https://pypi.org/project/pytest-xdist/#identifying-workers-from-the-system-environmentbas

Here is a way to see which test is running when pytest-xdist is processing.
Link to docs: https://docs.pytest.org/en/7.1.x/reference/reference.html#_pytest.hookspec.pytest_report_teststatus
Add the following function to your conftest.py file.
#conftest.py
def pytest_report_teststatus(report):
print(report.__dict__['nodeid'])
Example command to start pytest:
python -m pytest -n 3 -s --show-capture=no --disable-pytest-warnings

Using pytest, is it possible for a unit test to know that it is being run with code coverage monitoring on?

I am currently developing some tests using python py.test / unittest that, via subprocess, invoke another python application (so that I can exercise the command line options, and confirm that the tool is installed correctly).
I would like to be able to run the tests in such a way that I can get a view of the code coverage metrics (using coverage.py) for the target application using pytest_cov. By default this does not work as the code coverage instrumentation does not apply to code invoked with subprocess.
Code Coverage of the code does work if I update the tests to directly invoke the entry class for the target application (rather than running via the command line).
Ideally I want to have a single set of code which can be run in two ways:
If code coverage monitoring is not enabled then use command line
Otherwise execute the main class of the target application.
Which leads to my question(s):
Is it possible for a python unit test to determine if it is being run with code coverage enabled?
Otherwise: is there any easy way to pass a command line flag from the pytest invocation that can be used to set the mode within the code.

Coverage.py has a facility to automatically measure coverage in sub-processes that are spawned: http://coverage.readthedocs.io/en/latest/subprocess.html

Coverage sets three environment flags when running tests: COV_CORE_SOURCE, COV_CORE_CONFIG and COV_CORE_DATAFILE.
So you can use a simple if-statement to verify whether the current test is being run with coverage enabled:
import os
if "COV_CORE_SOURCE" in os.environ:
# do what yo need to do when Coverage is enabled

Make each run of python interpreter automatically call `coverage`?

I have test.sh that runs python command on many different scripts. Is there a way to emit coverage -a for each python call without prepending each command with coverage -a?

See the coverage.py docs about subprocess measurement for a way to invoke coverage automatically when starting Python: http://coverage.readthedocs.io/en/latest/subprocess.html . It will require some fiddling.
It might be easier to alias in the shell script. For things like "nosetests", change it to "python -m nose".

executing python unittest with ipdb

Typically I run my python unit test with:
python -m unittest test.<module-name>
I would like to debug my tests using ipdb but I cannot figure out how to invoke theunittest module in manner similar to the command above.
The directory structure is:
base/src for the source code
base/test for the test code
Tests run from the base directory.
The preference is to 'run' & 'debug' test cases in the same manner, specifically the preference is to debug with ipdb in a similar manner to the python command above.
FYI
Interpreter is python2

I don't know how to do this with the unittest module from the standardlib, but the testrunner pytest has at least pdb (not ipdb) support. Just invoke it with
pytest --pdb
and it drops into pdb with the first failure.

How can I query the enable status of a plugin in nose?

I'm currently trying to see if a nose plugin is enabled from within my test harness. The specific thing I'm trying to do is propagate the enable status of the coverage module to subprocess executions. Essentially when --with-coverage is used, I want to execute the subprocesses under the coverage tool directly (or propagate a flag down).
Can this be done?

This is one of those cases where you need to work around nose. See Measuring subprocesses in the coverage documentation for ways to ensure that subprocesses automatically invoke coverage.