kmuszyn/pytest-xprocess

pytest external process plugin

pytest-xprocess

Experimental py.test plugin for managing processes across test runs.

Usage

install via:

pip install pytest-xprocess

This will provide a xprocess fixture which helps you to ensure that one ore more longer-running processes are present for your tests. You can use it to start and pre-configure test-specific databases (Postgres, Couchdb, ...).

Additionally there are two new command line options:

--xkill  # terminates all external processes
--xshow  # shows currently running processes and log files

xprocess fixture usage

You typically define a project-specific fixture which uses the xprocess fixture internally:

# content of conftest.py

import pytest
from xprocess import ProcessStarter

@pytest.fixture
def myserver(xprocess):
    class Starter(ProcessStarter):
        pattern = "PATTERN"
        args = ['command', 'arg1', 'arg2']

    logfile = xprocess.ensure("myserver", Starter)
    conn = # create a connection or url/port info to the server
    return conn

The xprocess.ensure function takes a name for the external process because you can have multiple external processes.

The Starter is a subclass that gets initialized with the working directory created for this process. If the server has not yet been started:

• the args are used to invoke a new subprocess.
• the pattern is waited for in the logfile before returning. It should thus match a state of your server where it is ready to answer queries.
• env may be defined to customize the environment in which the new subprocess is invoked. To inherit the main test process environment, leave env set to the default (None).
• stdout is redirected to a logfile, which is returned pointing to the line right after the match

else, if the server is already running simply the logfile is returned.

To customize the startup behavior, override other methods of the ProcessStarter. For example, to extend the number of lines searched for the startup info:

class Starter(ProcessStarter):
    pattern = 'process started at .*'
    args = ['command', 'arg1']

    def filter_lines(self, lines):
        return itertools.islice(lines, 500)

To override the wait behavior, override :method:`ProcessStarter.wait`. See the :class:`xprocess.ProcessStarter` interface for more details.

Note that the plugin needs to persist the process ID and logfile information. It does this in a sub directory of the directory which contains a pytest.ini or setup.py file.