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This step runs a unit test suite using trial, a unittest-like testing framework that is a component of Twisted Python. Trial is used to implement Twisted's own unit tests, and is the unittest-framework of choice for many projects that use Twisted internally.

Projects that use trial typically have all their test cases in a 'test' subdirectory of their top-level library directory. For example, for a package petmail, the tests might be in petmail/test/test_*.py. More complicated packages (like Twisted itself) may have multiple test directories, like twisted/test/test_*.py for the core functionality and twisted/mail/test/test_*.py for the email-specific tests.

To run trial tests manually, you run the trial executable and tell it where the test cases are located. The most common way of doing this is with a module name. For petmail, this might look like trial petmail.test, which would locate all the test_*.py files under petmail/test/, running every test case it could find in them. Unlike the that comes with Python, it is not necessary to run the as a script; you always let trial do the importing and running. The step's tests parameter controls which tests trial will run: it can be a string or a list of strings.

To find the test cases, the Python search path must allow something like import petmail.test to work. For packages that don't use a separate top-level lib directory, PYTHONPATH=. will work, and will use the test cases (and the code they are testing) in-place. PYTHONPATH=build/lib or PYTHONPATH=build/lib.somearch are also useful when you do a python build step first. The testpath attribute of this class controls what PYTHONPATH is set to before running trial.

Trial has the ability, through the --testmodule flag, to run only the set of test cases named by special test-case-name tags in source files. We can get the list of changed source files from our parent Build and provide them to trial, thus running the minimal set of test cases needed to cover the Changes. This is useful for quick builds, especially in trees with a lot of test cases. The testChanges parameter controls this feature: if set, it will override tests.

The trial executable itself is typically just trial, and is typically found in the shell search path. It can be overridden with the trial parameter. This is useful for Twisted's own unittests, which want to use the copy of bin/trial that comes with the sources.

To influence the version of python being used for the tests, or to add flags to the command, set the python parameter. This can be a string (like python2.2) or a list (like ['python2.3', '-Wall']).

Trial creates and switches into a directory named _trial_temp/ before running the tests, and sends the twisted log (which includes all exceptions) to a file named test.log. This file will be pulled up to the master where it can be seen as part of the status output.

     from buildbot.steps.python_twisted import Trial