trial Man page



trial – run unit tests


trial [ options ] [ file | package | module | TestCase | testmethod ] …

trial –help | -h


trial loads and executes a suite of unit tests, obtained from modules,
packages and files listed on the command line.

trial will take either filenames or fully qualified Python names as
arguments. Thus `trial myproject/’, `trial’ and
`trial’ are all valid ways to
invoke trial. Multiple such arguments are also accepted, and their
order will determine the order in which the corresponding tests are

After running the given test suite, the default test reporter prints a
summary of the test run. This consists of the word “PASSED” (if all
tests ran as expected) or “FAILED” (if any test behaved unexpectedly)
followed by a count of the different kinds of test results encountered.
The possible kinds of test results includes:

Tests that passed all their assertions and completed without
error. These are marked “PASSED” in the normal test output.

Tests that failed an assertion, called or explicitly
raised self.failureException for some reason. These are marked
“FAILED” in the normal test output.

errors Tests that raised an unexpected exception (including Assertion‐
Error), tests that caused the tearDown() method to raise an
exception, tests that run for longer than the timeout interval,
tests that caused something to call twisted.python.log.err()
without subsequently calling self.flushLoggedErrors(), tests
that leave the reactor in an unclean state, etc. These are
marked “ERROR” in the normal test output.

Note that because errors can be caused after the actual test
method returns, it is possible for a single test to be reported
as both an error and a failure, and hence the total number of
test results can be greater than the total number of tests exe‐

skips Tests that were skipped, usually because of missing dependen‐
cies. These are marked “SKIPPED” in the normal test output.

Tests that failed, but were expected to fail, usually because
the test is for a feature that hasn’t been implemented yet.
These are marked “TODO” in the normal test output.

Tests that should have been listed under expectedFailures,
except that for some reason the test succeeded. These are marked
“SUCCESS!?!” in the normal test output.


-j, –jobs number
Set the number of process workers to run. It conflicts with the
debug, exitfirst and profile options.

-b, –debug
Run the tests in a debugger. If that debugger is ‘pdb’ (which is
the default if unspecified), a `.pdbrc’ will be loaded from the
current directory if it exists. Also does post-mortem debugging
on exceptions.

-B, –debug-stacktraces
Report Deferred creation and callback stack traces.

Generate coverage information in the `coverage’ subdirectory of
the trial temp directory (`_trial_temp’ by default). For each
Python module touched by the execution of the given tests, a
file will be created in the coverage directory named for the
module’s fully-qualified name with the suffix `.cover’. For
example, because the trial test runner is written in Python, the
coverage directory will almost always contain a file named

Each `.cover’ file contains a copy of the Python source of the
module in question, with a prefix at the beginning of each line
containing coverage information. For lines that are not exe‐
cutable (blank lines, comments, etc.) the prefix is blank. For
executable lines that were run in the course of the test suite,
the prefix is a number indicating the number of times that line
was executed. The string `>>>>>>’ prefixes executable lines
that were not executed in the course of the test suite.

Note that this functionality uses Python’s sys.settrace() func‐
tion, so tests that call sys.settrace() themselves are likely to
break trial’s coverage functionality.

Specifies the debugger to use when the –debug option is passed.
The argument should be the fully qualified name of an object
that implements the same interface as the standard library’s

Disable the garbage collector for the duration of the test run.
As each test is run, trial saves the TestResult objects, which
means that Python’s garbage collector has more non-garbage
objects to wade through, making each garbage-collection run
slightly slower. Disabling garbage collection entirely will make
some test suites complete faster (contrast –force-gc, below),
at the cost of increasing (possibly greatly) memory consumption.
This option also makes tests slightly more deterministic, which
might help debugging in extreme circumstances.

-e, –rterrors
Print tracebacks to standard output as soon as they occur.

Run gc.collect() before and after each test case. This can be
used to isolate errors that occur when objects get collected.
This option would be the default, except it makes tests run
about ten times slower.

-h, –help
Print a usage message to standard output, then exit.

Print a list of possible orders that TestCase test methods can
be run in, then exit. The orders can be used with the –order
option described below.

Print a list of valid reporters to standard output, then exit.
Reporters can be selected with the –reporter option described

Print a list of possible reactors to standard output, then exit.
Not all listed reactors are available on every platform. Reac‐
tors can be selected with the –reactor option described below.

-l, –logfile logfile
Direct the log to a different file. The default file is
`test.log’. logfile is relative to _trial_temp.

-n, –dry-run
Go through all the tests and make them pass without running.

-N, –no-recurse
By default, trial recurses through packages to find every module
inside every subpackage. Unless, that is, you specify this

–nopm Don’t automatically jump into debugger for post-mortem analysis
of exceptions. Only usable in conjunction with –debug.

–order order
Specify what order to run the individual test methods within the
given TestCases. By default, they are run alphabetically. See
–help-order for a list of other valid values.

Run tests under the Python profiler.

-r, –reactor reactor
Choose which reactor to use. See –help-reactors for a list.

–recursionlimit limit
Set Python’s recursion limit. See sys.setrecursionlimit().

–reporter reporter
Select the reporter to use for trial’s output. Use the –help-
reporters option to see a list of valid reporters.

-x, –exitfirst
Stop the test run after the first test which does not succeed.
This includes failures, errors, or unexpected successes. Won’t
work with the –jobs option currently.

–spew Print an insanely verbose log of everything that happens. Useful
when debugging freezes or locks in complex code.

–tbformat format
Format to display tracebacks with. Acceptable values are
`default’, `brief’ and `verbose’. `brief’ produces tracebacks
that play nicely with Emacs’ GUD.

–temp-directory directory
WARNING: Do not use this option unless you know what you are
doing. By default, trial creates a directory called _trial_temp
under the current working directory. When trial runs, it first
deletes this directory, then creates it, then changes into the
directory to run the tests. The log file and any coverage files
are stored here. Use this option if you wish to have trial run
in a directory other than _trial_temp. Be warned, trial will
delete the directory before re-creating it.

–testmodule filename
Ask trial to look into filename and run any tests specified
using the Emacs-style buffer variable `test-case-name’.

As of Twisted 8.0, trial will report an error if the reactor is
left unclean at the end of the test. This option is provided to
assist in migrating from Twisted 2.5 to Twisted 8.0 and later.
Enabling this option will turn the errors into warnings.

-u, –until-failure
Keep looping the tests until one of them raises an error or a
failure. This is particularly useful for reproducing intermit‐
tent failures.

Prints the Twisted version number and exit.

–without-module modulenames
Simulate the lack of the specified comma-separated list of mod‐
ules. This makes it look like the modules are not present in the
system, causing tests to check the behavior for that configura‐

-z, –random seed
Run the tests in random order using the specified seed. Don’t
pass this option if you also are passing –order.


The latest version of the trial documentation can be found at


Written by Jonathan M. Lange


To report a bug, visit


Copyright © 2003-2013 Twisted Matrix Laboratories
This is free software; see the source for copying conditions. There is

Jun 2013 TRIAL(1)