Develop Reference

Can i use regex within a pytest expression

Is it possible to locate tests with pytest using pattern matching, for example i want to find all tests that begin with the letters from a-m
i have been trying things like
pytest -m ^[aA-mM]
pytest --collectonly -k test_^[aA-mM] --quiet
Not got it to work so far, is this possible?

Doesn't seem possible according to pytest doc.
Have you considered marking the tests instead?
This helps with filtering them out when you run pytest.
More info about marking could be found in the pytest doc about markers...
or another tutorial about it
But in short, for example:
just add #pytest.mark.foo onto some tests, and #pytest.mark.bar to others
run pytest -m foo to run the tests marked as foo only.

How to designate Python unit tests as having database dependency?

I am working on a project that has many "unit tests" that have hard dependencies that need to interact with the database and other APIs. The tests are a valuable and useful resource to our team, but they just cannot be ran independently, without relying on the functionality of other services within the test environment. Personally I would call these "functional tests", but this is just the semantics already established within our team.
The problem is, now that we are beginning to introduce more pure unit tests into our code, we have a medley of tests that do or do not have external dependencies. These tests can be ran immediately after checking out code with no requirement to install or configure other tools. They can also be ran in a continuous integration environment like jenkins.
So my question is, how I can denote which is which for a cleaner separation? Is there an existing decorator within unit testing library?

You can define which test should be skipped with the skipIf decorator. In combinations with setting an environmental variable you can skip tests in some environments. An example:
from unittest import skipIf
class MyTest(Testcase):
#skipIf(os.environ.get('RUNON') == 'jenkins', 'Does not run in Jenkins')
def test_my_code(self):
...

Here's another option. You could separate different test categories by directory. If you wanted to try this strategy, it may look something like:
python
-modules
unit
-pure unit test modules
functional
-other unit test modules
In your testing pipeline, you can call your testing framework to only execute the desired tests. For example, with Python's unittest, you could run your 'pure unit tests' from within the python directory with
python -m unittest discover --start-directory ../unit
and the functional/other unit tests with
python -m unittest discover --start-directory ../functional
An advantage of this setup is that your tests are easily categorized and you can do any scaffolding or mocked up services that you need in each testing environment. Someone with a little more Python experience might be able to help you run the tests regardless of the current directory, too.

Python benchmark tool like nosetests?

What I want
I would like to create a set of benchmarks for my Python project. I would like to see the performance of these benchmarks change as I introduce new code. I would like to do this in the same way that I test Python, by running the utility command like nosetests and getting a nicely formatted readout.
What I like about nosetests
The nosetests tool works by searching through my directory structure for any functions named test_foo.py and runs all functions test_bar() contained within. It runs all of those functions and prints out whether or not they raised an exception.
I'd like something similar that searched for all files bench_foo.py and ran all contained functions bench_bar() and reported their runtimes.
Questions
Does such a tool exist?
If not what are some good starting points? Is some of the nose source appropriate for this?

nosetests can run any type of test, so you can decide if they test functionality, input/output validity etc., or performance or profiling (or anything else you'd like). The Python Profiler is a great tool, and it comes with your Python installation.
import unittest
import cProfile
class ProfileTest(unittest.TestCase):
test_run_profiler:
cProfile.run('foo(bar)')
cProfile.run('baz(bar)')
You just add a line to the test, or add a test to the test case for all the calls you want to profile, and your main source is not polluted with test code.
If you only want to time execution and not all the profiling information, timeit is another useful tool.

The wheezy documentation has a good example on how to do this with nose. The important part if you just want to have the timings is to use options -q for quiet run, -s for not capturing the output (so you will see the output of the report) and -m benchmark to only run the 'timing' tests.
I recommend using py.test for testing over. To run the example from wheezy with that, change the name of the runTest method to test_bench_run and run only this benchmark with:
py.test -qs -k test_bench benchmark_hello.py
(-q and -s having the same effect as with nose and -k to select the pattern of the test names).
If you put your benchmark tests in file in a separate file or directory from normal tests they are of course more easy to select and don't need special names.

unittest colored output

I use unittest (actually unittest2) for Python testing, together with Python Mock for mocking objects and nose to run all tests in a single pass.
I miss being able to tell what is working and what's wrong at a glance from the green/red bars. Is there a way to get colored output from unittest?
(Changing test suite at this point is not an option, and I actually like unittest)

Using a method very similar to robert's answer, I have (today!) released a package that enables colour output in unittest test results. I have called it colour-runner.
To install it, run:
pip install colour-runner
Then, where you were using unittest.TextTestRunner, use colour_runner.runner.ColourTextTestRunner instead.
See how it looks with verbosity=1...and verbosity=2

I'm having good success with nosetests and rednose. It's still maintained at the time of writing this.

In python 2.x you could try pyrg. Does not work in Python 3 though.

Make a class that inherits from unittest.TestResult (say, MyResults) and implements a bunch of methods. Then make a class that inherits from unittest.TextTestRunner (say, MyRunner) and override _makeResult() to return an instance of MyResults.
Then, construct a test suite (which you've probably already got working), and call MyRunner().run(suite).
You can put whatever behavior you like, including colors, into MyResults.

If you are running pytest this way:
python -m unittest test_my.py
Change it to:
pytest test_my.py
And you get colors for free

pytest can do this with no changes needed for unit tests.
Now install pytest.
pip install --user pytest
And run the tests to see the color!

If you could change just the line of your test imports, you could use redgreenunittest. It's a clone I made of unittest, but it has colorized output.
If you want to use it without updating any of the meat of your code, you can just use it like so:
import redgreenunittest as unittest
It's not a clone of unittest2, so it wouldn't work out-of-the-box with Andrea's code, but its source is right there, so a unittest2 fork of redgreenunittest wouldn't be out of the question.
Also, any "you're doing it wrong" comments are welcome, so long as they contain some reasoning. I'd love to do it right instead.

I've also found another colouring plugin for nose: YANC at https://pypi.python.org/pypi/yanc
Works for me with Python 3.5 and nose 1.3.7 (I couldn't get any of the other options for nose listed above to work)

Try rudolf plugin for nosetests.

use/run python's 2to3 as or like a unittest

I have used the 2to3 utility to convert code from the command line. What I would like to do is run it basically as a unittest. Even if it tests the file rather than parts(functions, methods...) as would be normal for a unittest.
It does not need to be a unittest and I don't what to automatically convert the files I just want to monitor the py3 compliance of files in a unittest like manor. I can't seem to find any documentation or examples for this.
An example and/or documentation would be great.

Simply use the -3 option with python2.6+ to be informed of Python3 compliance.

If you are trying to verify the code will work in Python 3.x, I would suggest a script that copies the source files to a new directory, runs 2to3 on them, then copies the unit tests to the directory and runs them.
This may seem slightly inelegant, but is consistent with the spirit of unit testing. You are making a series of assertions that you believe ought to be true about the external behavior of the code, regardless of implementation. If the converted code passes your unit tests, you can consider your code to support Python 3.