========================================
doctest -- Testing through documentation
========================================
.. module:: doctest
:synopsis: Write automated tests as part of the documentation for a module.
:Purpose: Write automated tests as part of the documentation for a module.
:Python Version: 2.1
:mod:`doctest` lets you test your code by running examples embedded in
the documentation and verifying that they produce the expected
results. It works by parsing the help text to find examples, running
them, then comparing the output text against the expected value. Many
developers find :mod:`doctest` easier than :mod:`unittest` because in
its simplest form, there is no API to learn before using it. However,
as the examples become more complex the lack of fixture management can
make writing :mod:`doctest` tests more cumbersome than using
:mod:`unittest`.
Getting Started
===============
The first step to setting up doctests is to use the interactive
interpreter to create examples and then copy and paste them into the
docstrings in your module. Here, :func:`my_function` has two examples
given:
.. include:: doctest_simple.py
:literal:
:start-after: #end_pymotw_header
To run the tests, use :mod:`doctest` as the main program via the
``-m`` option to the interpreter. Usually no output is produced while
the tests are running, so the example below includes the ``-v`` option
to make the output more verbose.
.. {{{cog
.. cog.out(run_script(cog.inFile, '-m doctest -v doctest_simple.py'))
.. }}}
::
$ python -m doctest -v doctest_simple.py
Trying:
my_function(2, 3)
Expecting:
6
ok
Trying:
my_function('a', 3)
Expecting:
'aaa'
ok
1 items had no tests:
doctest_simple
1 items passed all tests:
2 tests in doctest_simple.my_function
2 tests in 2 items.
2 passed and 0 failed.
Test passed.
.. {{{end}}}
Examples cannot usually stand on their own as explanations of a
function, so :mod:`doctest` also lets you keep the surrounding text
you would normally include in the documentation. It looks for lines
beginning with the interpreter prompt, ``>>>``, to find the beginning
of a test case. The case is ended by a blank line, or by the next
interpreter prompt. Intervening text is ignored, and can have any
format as long as it does not look like a test case.
.. include:: doctest_simple_with_docs.py
:literal:
:start-after: #end_pymotw_header
The surrounding text in the updated docstring makes it more useful to
a human reader, and is ignored by :mod:`doctest`, and the results are
the same.
.. {{{cog
.. cog.out(run_script(cog.inFile, '-m doctest -v doctest_simple_with_docs.py'))
.. }}}
::
$ python -m doctest -v doctest_simple_with_docs.py
Trying:
my_function(2, 3)
Expecting:
6
ok
Trying:
my_function('a', 3)
Expecting:
'aaa'
ok
1 items had no tests:
doctest_simple_with_docs
1 items passed all tests:
2 tests in doctest_simple_with_docs.my_function
2 tests in 2 items.
2 passed and 0 failed.
Test passed.
.. {{{end}}}
Handling Unpredictable Output
=============================
There are other cases where the exact output may not be predictable,
but should still be testable. Local date and time values and object
ids change on every test run. The default precision used in the
representation of floating point values depend on compiler options.
Object string representations may not be deterministic. Although
these conditions are outside of your control, there are techniques for
dealing with them.
For example, in CPython, object identifiers are based on the memory
address of the data structure holding the object.
.. include:: doctest_unpredictable.py
:literal:
:start-after: #end_pymotw_header
These id values change each time a program runs, because it is loaded
into a different part of memory.
.. {{{cog
.. cog.out(run_script(cog.inFile, '-m doctest -v doctest_unpredictable.py', ignore_error=True))
.. }}}
::
$ python -m doctest -v doctest_unpredictable.py
Trying:
unpredictable(MyClass())
Expecting:
[<doctest_unpredictable.MyClass object at 0x10055a2d0>]
**********************************************************************
File "doctest_unpredictable.py", line 16, in doctest_unpredictable.unpredictable
Failed example:
unpredictable(MyClass())
Expected:
[<doctest_unpredictable.MyClass object at 0x10055a2d0>]
Got:
[<doctest_unpredictable.MyClass object at 0x100563490>]
2 items had no tests:
doctest_unpredictable
doctest_unpredictable.MyClass
**********************************************************************
1 items had failures:
1 of 1 in doctest_unpredictable.unpredictable
1 tests in 3 items.
0 passed and 1 failed.
***Test Failed*** 1 failures.
.. {{{end}}}
When the tests include values that are likely to change in
unpredictable ways, and where the actual value is not important to the
test results, you can use the ``ELLIPSIS`` option to tell
:mod:`doctest` to ignore portions of the verification value.
.. include:: doctest_ellipsis.py
:literal:
:start-after: #end_pymotw_header
The comment after the call to :func:`unpredictable` (``#doctest:
+ELLIPSIS``) tells :mod:`doctest` to turn on the ``ELLIPSIS`` option
for that test. The ``...`` replaces the memory address in the object
id, so that portion of the expected value is ignored and the actual
output matches and the test passes.
.. {{{cog
.. cog.out(run_script(cog.inFile, '-m doctest -v doctest_ellipsis.py'))
.. }}}
::
$ python -m doctest -v doctest_ellipsis.py
Trying:
unpredictable(MyClass()) #doctest: +ELLIPSIS
Expecting:
[<doctest_ellipsis.MyClass object at 0x...>]
ok
2 items had no tests:
doctest_ellipsis
doctest_ellipsis.MyClass
1 items passed all tests:
1 tests in doctest_ellipsis.unpredictable
1 tests in 3 items.
1 passed and 0 failed.
Test passed.
.. {{{end}}}
There are cases where you cannot ignore the unpredictable value,
because that would obviate the test. For example, simple tests
quickly become more complex when dealing with data types whose string
representations are inconsistent. The string form of a dictionary,
for example, may change based on the order the keys are added.
.. include:: doctest_hashed_values.py
:literal:
:start-after: #end_pymotw_header
Because of cache collision, the internal key list order is different
for the two dictionaries, even though they contain the same values and
are considered to be equal. Sets use the same hashing algorithm, and
exhibit the same behavior.
.. {{{cog
.. cog.out(run_script(cog.inFile, 'doctest_hashed_values.py'))
.. }}}
::
$ python doctest_hashed_values.py
d1: {'a': 1, 'aa': 2, 'aaa': 3}
d2: {'aa': 2, 'a': 1, 'aaa': 3}
d1 == d2: True
s1: set(['a', 'aa', 'aaa'])
s2: set(['aa', 'a', 'aaa'])
s1 == s2: True
.. {{{end}}}
The best way to deal with these potential discrepancies is to create
tests that produce values that are not likely to change. In the case
of dictionaries and sets, that might mean looking for specific keys
individually, generating a sorted list of the contents of the data
structure, or comparing against a literal value for equality instead
of depending on the string representation.
.. include:: doctest_hashed_values_tests.py
:literal:
:start-after: #end_pymotw_header
Notice that the single example is actually interpreted as two separate
tests, with the first expecting no console output and the second
expecting the boolean result of the comparison operation.
.. {{{cog
.. cog.out(run_script(cog.inFile, '-m doctest -v doctest_hashed_values_tests.py'))
.. }}}
::
$ python -m doctest -v doctest_hashed_values_tests.py
Trying:
grouped = group_by_length([ 'python', 'module', 'of', 'the', 'week' ])
Expecting nothing
ok
Trying:
grouped == { 2:set(['of']),
3:set(['the']),
4:set(['week']),
6:set(['python', 'module']),
}
Expecting:
True
ok
1 items had no tests:
doctest_hashed_values_tests
1 items passed all tests:
2 tests in doctest_hashed_values_tests.group_by_length
2 tests in 2 items.
2 passed and 0 failed.
Test passed.
.. {{{end}}}
Tracebacks
==========
Tracebacks are a special case of changing data. Since the paths in a
traceback depend on the location where a module is installed on the
filesystem on a given system, it would be impossible to write portable
tests if they were treated the same as other output.
.. include:: doctest_tracebacks.py
:literal:
:start-after: #end_pymotw_header
:mod:`doctest` makes a special effort to recognize tracebacks, and
ignore the parts that might change from system to system.
.. {{{cog
.. cog.out(run_script(cog.inFile, '-m doctest -v doctest_tracebacks.py'))
.. }}}
::
$ python -m doctest -v doctest_tracebacks.py
Trying:
this_raises()
Expecting:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/no/such/path/doctest_tracebacks.py", line 14, in this_raises
raise RuntimeError('here is the error')
RuntimeError: here is the error
ok
1 items had no tests:
doctest_tracebacks
1 items passed all tests:
1 tests in doctest_tracebacks.this_raises
1 tests in 2 items.
1 passed and 0 failed.
Test passed.
.. {{{end}}}
In fact, the entire body of the traceback is ignored and can be
omitted.
.. include:: doctest_tracebacks_no_body.py
:literal:
:start-after: #end_pymotw_header
When :mod:`doctest` sees a traceback header line (either ``Traceback
(most recent call last):`` or ``Traceback (innermost last):``,
depending on the version of Python you are running), it skips ahead to
find the exception type and message, ignoring the intervening lines
entirely.
.. {{{cog
.. cog.out(run_script(cog.inFile, '-m doctest -v doctest_tracebacks_no_body.py'))
.. }}}
::
$ python -m doctest -v doctest_tracebacks_no_body.py
Trying:
this_raises()
Expecting:
Traceback (most recent call last):
RuntimeError: here is the error
ok
1 items had no tests:
doctest_tracebacks_no_body
1 items passed all tests:
1 tests in doctest_tracebacks_no_body.this_raises
1 tests in 2 items.
1 passed and 0 failed.
Test passed.
.. {{{end}}}
Working Around Whitespace
=========================
In real world applications, output usually includes whitespace such as
blank lines, tabs, and extra spacing to make it more readable. Blank
lines, in particular, cause issues with :mod:`doctest` because they
are used to delimit tests.
.. include:: doctest_blankline_fail.py
:literal:
:start-after: #end_pymotw_header
:func:`double_space` takes a list of input lines, and prints them
double-spaced with blank lines between.
.. {{{cog
.. cog.out(run_script(cog.inFile, '-m doctest doctest_blankline_fail.py', ignore_error=True))
.. }}}
::
$ python -m doctest doctest_blankline_fail.py
**********************************************************************
File "doctest_blankline_fail.py", line 13, in doctest_blankline_fail.double_space
Failed example:
double_space(['Line one.', 'Line two.'])
Expected:
Line one.
Got:
Line one.
<BLANKLINE>
Line two.
<BLANKLINE>
**********************************************************************
1 items had failures:
1 of 1 in doctest_blankline_fail.double_space
***Test Failed*** 1 failures.
.. {{{end}}}
The test fails, because it interprets the blank line after ``Line
one.`` in the docstring as the end of the sample output. To match the
blank lines, replace them in the sample input with the string
``<BLANKLINE>``.
.. include:: doctest_blankline.py
:literal:
:start-after: #end_pymotw_header
:mod:`doctest` replaces actual blank lines with the same literal
before performing the comparison, so now the actual and expected
values match and the test passes.
.. {{{cog
.. cog.out(run_script(cog.inFile, '-m doctest -v doctest_blankline.py'))
.. }}}
::
$ python -m doctest -v doctest_blankline.py
Trying:
double_space(['Line one.', 'Line two.'])
Expecting:
Line one.
<BLANKLINE>
Line two.
<BLANKLINE>
ok
1 items had no tests:
doctest_blankline
1 items passed all tests:
1 tests in doctest_blankline.double_space
1 tests in 2 items.
1 passed and 0 failed.
Test passed.
.. {{{end}}}
Another pitfall of using text comparisons for tests is that embedded
whitespace can also cause tricky problems with tests. This example
has a single extra space after the ``6``.
.. include:: doctest_extra_space.py
:literal:
:start-after: #end_pymotw_header
Extra spaces can find their way into your code via copy-and-paste
errors, but since they come at the end of the line, they can go
unnoticed in the source file and be invisible in the test failure
report as well.
.. {{{cog
.. cog.out(run_script(cog.inFile, '-m doctest -v doctest_extra_space.py', ignore_error=True))
.. }}}
::
$ python -m doctest -v doctest_extra_space.py
Trying:
my_function(2, 3)
Expecting:
6
**********************************************************************
File "doctest_extra_space.py", line 12, in doctest_extra_space.my_function
Failed example:
my_function(2, 3)
Expected:
6
Got:
6
Trying:
my_function('a', 3)
Expecting:
'aaa'
ok
1 items had no tests:
doctest_extra_space
**********************************************************************
1 items had failures:
1 of 2 in doctest_extra_space.my_function
2 tests in 2 items.
1 passed and 1 failed.
***Test Failed*** 1 failures.
.. {{{end}}}
Using one of the diff-based reporting options, such as
``REPORT_NDIFF``, shows the difference between the actual and expected
values with more detail, and the extra space becomes visible.
.. include:: doctest_ndiff.py
:literal:
:start-after: #end_pymotw_header
Unified (``REPORT_UDIFF``) and context (``REPORT_CDIFF``) diffs are
also available, for output where those formats are more readable.
.. {{{cog
.. cog.out(run_script(cog.inFile, '-m doctest -v doctest_ndiff.py', ignore_error=True))
.. }}}
::
$ python -m doctest -v doctest_ndiff.py
Trying:
my_function(2, 3) #doctest: +REPORT_NDIFF
Expecting:
6
**********************************************************************
File "doctest_ndiff.py", line 12, in doctest_ndiff.my_function
Failed example:
my_function(2, 3) #doctest: +REPORT_NDIFF
Differences (ndiff with -expected +actual):
- 6
? -
+ 6
Trying:
my_function('a', 3)
Expecting:
'aaa'
ok
1 items had no tests:
doctest_ndiff
**********************************************************************
1 items had failures:
1 of 2 in doctest_ndiff.my_function
2 tests in 2 items.
1 passed and 1 failed.
***Test Failed*** 1 failures.
.. {{{end}}}
There are cases where it is beneficial to add extra whitespace in the
sample output for the test, and have :mod:`doctest` ignore it. For
example, data structures can be easier to read when spread across
several lines, even if their representation would fit on a single
line.
.. include:: doctest_normalize_whitespace.py
:literal:
:start-after: #end_pymotw_header
When ``NORMALIZE_WHITESPACE`` is turned on, any whitespace in the
actual and expected values is considered a match. You cannot add
whitespace to the expected value where none exists in the output, but
the length of the whitespace sequence and actual whitespace characters
do not need to match. The first test example gets this rule correct,
and passes, even though there are extra spaces and newlines. The
second has extra whitespace after ``[`` and before ``]``, so it fails.
.. {{{cog
.. cog.out(run_script(cog.inFile, '-m doctest -v doctest_normalize_whitespace.py', ignore_error=True))
.. }}}
::
$ python -m doctest -v doctest_normalize_whitespace.py
Trying:
my_function(['A', 'B', 'C'], 3) #doctest: +NORMALIZE_WHITESPACE
Expecting:
['A', 'B', 'C',
'A', 'B', 'C',
'A', 'B', 'C']
ok
Trying:
my_function(['A', 'B', 'C'], 2) #doctest: +NORMALIZE_WHITESPACE
Expecting:
[ 'A', 'B', 'C',
'A', 'B', 'C' ]
**********************************************************************
File "doctest_normalize_whitespace.py", line 20, in doctest_normalize_whitespace.my_function
Failed example:
my_function(['A', 'B', 'C'], 2) #doctest: +NORMALIZE_WHITESPACE
Expected:
[ 'A', 'B', 'C',
'A', 'B', 'C' ]
Got:
['A', 'B', 'C', 'A', 'B', 'C']
1 items had no tests:
doctest_normalize_whitespace
**********************************************************************
1 items had failures:
1 of 2 in doctest_normalize_whitespace.my_function
2 tests in 2 items.
1 passed and 1 failed.
***Test Failed*** 1 failures.
.. {{{end}}}
Test Locations
==============
All of the tests in the examples so far have been written in the
docstrings of the functions they are testing. That is convenient for
users who examine the docstrings for help using the funcion
(especially with :mod:`pydoc`), but :mod:`doctest` looks for tests in
other places, too. The obvious location for additional tests is in
the docstrings elsewhere in the module.
.. include:: doctest_docstrings.py
:literal:
Every docstring can contain tests at the module, class and function
level.
.. {{{cog
.. cog.out(run_script(cog.inFile, '-m doctest -v doctest_docstrings.py'))
.. }}}
::
$ python -m doctest -v doctest_docstrings.py
Trying:
A('a') == B('b')
Expecting:
False
ok
Trying:
A('instance_name').name
Expecting:
'instance_name'
ok
Trying:
A('name').method()
Expecting:
'eman'
ok
Trying:
B('different_name').name
Expecting:
'different_name'
ok
1 items had no tests:
doctest_docstrings.A.__init__
4 items passed all tests:
1 tests in doctest_docstrings
1 tests in doctest_docstrings.A
1 tests in doctest_docstrings.A.method
1 tests in doctest_docstrings.B
4 tests in 5 items.
4 passed and 0 failed.
Test passed.
.. {{{end}}}
In cases where you have tests that you want to include with your
source code, but do not want to have appear in the help for your
module, you need to put them somewhere other than the docstrings.
:mod:`doctest` also looks for a module-level variable called
``__test__`` and uses it to locate other tests. ``__test__`` should
be a dictionary mapping test set names (as strings) to strings,
modules, classes, or functions.
.. include:: doctest_private_tests.py
:literal:
:start-after: #end_pymotw_header
If the value associated with a key is a string, it is treated as a
docstring and scanned for tests. If the value is a class or function,
:mod:`doctest` searchs them recursivesly for docstrings, which are
then scanned for tests. In this example, the module
:mod:`doctest_private_tests_external` has a single test in its
docstring.
.. include:: doctest_private_tests_external.py
:literal:
:mod:`doctest` finds a total of five tests to run.
.. {{{cog
.. cog.out(run_script(cog.inFile, '-m doctest -v doctest_private_tests.py'))
.. }}}
::
$ python -m doctest -v doctest_private_tests.py
Trying:
my_function(['A', 'B', 'C'], 2)
Expecting:
['A', 'B', 'C', 'A', 'B', 'C']
ok
Trying:
my_function(2, 3)
Expecting:
6
ok
Trying:
my_function(2.0, 3)
Expecting:
6.0
ok
Trying:
my_function('a', 3)
Expecting:
'aaa'
ok
Trying:
my_function(3, 'a')
Expecting:
'aaa'
ok
2 items had no tests:
doctest_private_tests
doctest_private_tests.my_function
3 items passed all tests:
1 tests in doctest_private_tests.__test__.external
2 tests in doctest_private_tests.__test__.numbers
2 tests in doctest_private_tests.__test__.strings
5 tests in 5 items.
5 passed and 0 failed.
Test passed.
.. {{{end}}}
External Documentation
======================
Mixing tests in with your code isn't the only way to use
:mod:`doctest`. Examples embedded in external project documentation
files, such as reStructuredText files, can be used as well.
.. include:: doctest_in_help.py
:literal:
:start-after: #end_pymotw_header
The help for :mod:`doctest_in_help` is saved to a separate file,
``doctest_in_help.rst``. The examples illustrating how to use the
module are included with the help text, and :mod:`doctest` can be used
to find and run them.
.. include:: doctest_in_help.rst
:literal:
The tests in the text file can be run from the command line, just as
with the Python source modules.
.. {{{cog
.. cog.out(run_script(cog.inFile, '-m doctest -v doctest_in_help.rst'))
.. }}}
::
$ python -m doctest -v doctest_in_help.rst
Trying:
from doctest_in_help import my_function
Expecting nothing
ok
Trying:
my_function(2, 3)
Expecting:
6
ok
Trying:
my_function(2.0, 3)
Expecting:
6.0
ok
Trying:
my_function('a', 3)
Expecting:
'aaa'
ok
Trying:
my_function(['A', 'B', 'C'], 2)
Expecting:
['A', 'B', 'C', 'A', 'B', 'C']
ok
1 items passed all tests:
5 tests in doctest_in_help.rst
5 tests in 1 items.
5 passed and 0 failed.
Test passed.
.. {{{end}}}
Normally :mod:`doctest` sets up the test execution environment to
include the members of the module being tested, so your tests don't
need to import the module explicitly. In this case, however, the
tests aren't defined in a Python module, :mod:`doctest` does not know
how to set up the global namespace, so the examples need to do the
import work themselves. All of the tests in a given file share the
same execution context, so importing the module once at the top of the
file is enough.
Running Tests
=============
The previous examples all use the command line test runner built into
:mod:`doctest`. It is easy and convenient for a single module, but
will quickly become tedious as your package spreads out into multiple
files. There are several alternative approaches.
By Module
---------
You can include instructions to run :mod:`doctest` against your source
at the bottom of your modules. Use :func:`testmod` without any
arguments to test the current module.
.. include:: doctest_testmod.py
:literal:
:start-after: #end_pymotw_header
Ensure the tests are only run when the module is called as a main
program by invoking :func:`testmod` only if the current module name is
``__main__``.
.. {{{cog
.. cog.out(run_script(cog.inFile, 'doctest_testmod.py -v'))
.. }}}
::
$ python doctest_testmod.py -v
Trying:
my_function(2, 3)
Expecting:
6
ok
Trying:
my_function('a', 3)
Expecting:
'aaa'
ok
1 items had no tests:
__main__
1 items passed all tests:
2 tests in __main__.my_function
2 tests in 2 items.
2 passed and 0 failed.
Test passed.
.. {{{end}}}
The first argument to :func:`testmod` is a module containing code to
be scanned for tests. This feature lets you create a separate test
script that imports your real code and runs the tests in each module
one after another.
.. include:: doctest_testmod_other_module.py
:literal:
:start-after: #end_pymotw_header
You can build a test suite for your project by importing each module
and running its tests.
.. {{{cog
.. cog.out(run_script(cog.inFile, 'doctest_testmod_other_module.py -v'))
.. }}}
::
$ python doctest_testmod_other_module.py -v
Trying:
my_function(2, 3)
Expecting:
6
ok
Trying:
my_function('a', 3)
Expecting:
'aaa'
ok
1 items had no tests:
doctest_simple
1 items passed all tests:
2 tests in doctest_simple.my_function
2 tests in 2 items.
2 passed and 0 failed.
Test passed.
.. {{{end}}}
By File
-------
:func:`testfile` works in a way similar to :func:`testmod`, allowing
you to explicitly invoke the tests in an external file from within
your test program.
.. include:: doctest_testfile.py
:literal:
:start-after: #end_pymotw_header
.. {{{cog
.. cog.out(run_script(cog.inFile, 'doctest_testfile.py -v'))
.. }}}
::
$ python doctest_testfile.py -v
Trying:
from doctest_in_help import my_function
Expecting nothing
ok
Trying:
my_function(2, 3)
Expecting:
6
ok
Trying:
my_function(2.0, 3)
Expecting:
6.0
ok
Trying:
my_function('a', 3)
Expecting:
'aaa'
ok
Trying:
my_function(['A', 'B', 'C'], 2)
Expecting:
['A', 'B', 'C', 'A', 'B', 'C']
ok
1 items passed all tests:
5 tests in doctest_in_help.rst
5 tests in 1 items.
5 passed and 0 failed.
Test passed.
.. {{{end}}}
Both :func:`testmod` and :func:`testfile` include optional parameters
to let you control the behavior of the tests through the
:mod:`doctest` options, global namespace for the tests, etc. Refer to
the standard library documentation for more details if you need those
features -- most of the time you won't need them.
Unittest Suite
--------------
If you use both :mod:`unittest` and :mod:`doctest` for testing the
same code in different situations, you may find the :mod:`unittest`
integration in :mod:`doctest` useful for running the tests together.
Two classes, :class:`DocTestSuite` and :class:`DocFileSuite` create
test suites compatible with the test-runner API of :mod:`unittest`.
.. include:: doctest_unittest.py
:literal:
:start-after: #end_pymotw_header
The tests from each source are collapsed into a single outcome,
instead of being reported individually.
.. {{{cog
.. cog.out(run_script(cog.inFile, 'doctest_unittest.py'))
.. }}}
::
$ python doctest_unittest.py
my_function (doctest_simple)
Doctest: doctest_simple.my_function ... ok
doctest_in_help.rst
Doctest: doctest_in_help.rst ... ok
----------------------------------------------------------------------
Ran 2 tests in 0.006s
OK
.. {{{end}}}
Test Context
============
The execution context created by :mod:`doctest` as it runs tests
contains a copy of the module-level globals for the module containing
your code. This isolates the tests from each other somewhat, so they
are less likely to interfere with one another. Each test source
(function, class, module) has its own set of global values.
.. include:: doctest_test_globals.py
:literal:
:start-after: #end_pymotw_header
:class:`TestGlobals` has two methods, :func:`one` and :func:`two`.
The tests in the docstring for :func:`one` set a global variable, and
the test for :func:`two` looks for it (expecting not to find it).
.. {{{cog
.. cog.out(run_script(cog.inFile, '-m doctest -v doctest_test_globals.py'))
.. }}}
::
$ python -m doctest -v doctest_test_globals.py
Trying:
var = 'value'
Expecting nothing
ok
Trying:
'var' in globals()
Expecting:
True
ok
Trying:
'var' in globals()
Expecting:
False
ok
2 items had no tests:
doctest_test_globals
doctest_test_globals.TestGlobals
2 items passed all tests:
2 tests in doctest_test_globals.TestGlobals.one
1 tests in doctest_test_globals.TestGlobals.two
3 tests in 4 items.
3 passed and 0 failed.
Test passed.
.. {{{end}}}
That does not mean the tests *cannot* interfere with each other,
though, if they change the contents of mutable variables defined in
the module.
.. include:: doctest_mutable_globals.py
:literal:
:start-after: #end_pymotw_header
The module varabile ``_module_data`` is changed by the tests for
:func:`one`, causing the test for :func:`two` to fail.
.. {{{cog
.. cog.out(run_script(cog.inFile, '-m doctest -v doctest_mutable_globals.py', ignore_error=True))
.. }}}
::
$ python -m doctest -v doctest_mutable_globals.py
Trying:
TestGlobals().one()
Expecting nothing
ok
Trying:
'var' in _module_data
Expecting:
True
ok
Trying:
'var' in _module_data
Expecting:
False
**********************************************************************
File "doctest_mutable_globals.py", line 24, in doctest_mutable_globals.TestGlobals.two
Failed example:
'var' in _module_data
Expected:
False
Got:
True
2 items had no tests:
doctest_mutable_globals
doctest_mutable_globals.TestGlobals
1 items passed all tests:
2 tests in doctest_mutable_globals.TestGlobals.one
**********************************************************************
1 items had failures:
1 of 1 in doctest_mutable_globals.TestGlobals.two
3 tests in 4 items.
2 passed and 1 failed.
***Test Failed*** 1 failures.
.. {{{end}}}
If you need to set global values for the tests, to parameterize them
for an environment for example, you can pass values to :func:`testmod`
and :func:`testfile` and have the context set up using data you
control.
.. seealso::
`doctest <http://docs.python.org/library/doctest.html>`_
The standard library documentation for this module.
`The Mighty Dictionary <http://blip.tv/file/3332763>`__
Presentation by Brandon Rhodes at PyCon 2010 about the
internal operations of the :class:`dict`.
:mod:`difflib`
Python's sequence difference computation library, used to
produce the ndiff output.
`Sphinx <http://sphinx.pocoo.org/>`_
As well as being the documentation processing tool for
Python's standard library, Sphinx has been adopted by many
third-party projects because it is easy to use and produces
clean output in several digital and print formats. Sphinx
includes an extension for running doctests as is processes
your documentation, so you know your examples are always
accurate.
`nose <http://somethingaboutorange.com/mrl/projects/nose/>`_
Third-party test runner with :mod:`doctest` support.
`py.test <http://codespeak.net/py/dist/test/>`_
Third-party test runner with :mod:`doctest` support.
`Manuel <http://packages.python.org/manuel/>`_
Third-party documentation-based test runner with more advanced
test case extraction and integration with Sphinx.