Doctest integration for modules and test files

By default all files matching the test*.txt pattern will be run through the python standard doctest module. You can change the pattern by issuing:

pytest --doctest-glob='*.rst'

on the command line. Since version 2.9, --doctest-glob can be given multiple times in the command-line.

New in version 3.1: You can specify the encoding that will be used for those doctest files using the doctest_encoding ini option:

# content of pytest.ini
[pytest]
doctest_encoding = latin1

The default encoding is UTF-8.

You can also trigger running of doctests from docstrings in all python modules (including regular python test modules):

pytest --doctest-modules

You can make these changes permanent in your project by putting them into a pytest.ini file like this:

# content of pytest.ini
[pytest]
addopts = --doctest-modules

If you then have a text file like this:

# content of example.rst

hello this is a doctest
>>> x = 3
>>> x
3

and another like this:

# content of mymodule.py
def something():
    """ a doctest in a docstring
    >>> something()
    42
    """
    return 42

then you can just invoke pytest without command line options:

$ pytest
======= test session starts ========
platform linux -- Python 3.x.y, pytest-3.x.y, py-1.x.y, pluggy-0.x.y
rootdir: $REGENDOC_TMPDIR, inifile: pytest.ini
collected 1 item

mymodule.py .

======= 1 passed in 0.12 seconds ========

It is possible to use fixtures using the getfixture helper:

# content of example.rst
>>> tmp = getfixture('tmpdir')
>>> ...
>>>

Also, Using fixtures from classes, modules or projects and Autouse fixtures (xUnit setup on steroids) fixtures are supported when executing text doctest files.

The standard doctest module provides some setting flags to configure the strictness of doctest tests. In pytest You can enable those flags those flags using the configuration file. To make pytest ignore trailing whitespaces and ignore lengthy exception stack traces you can just write:

[pytest]
doctest_optionflags= NORMALIZE_WHITESPACE IGNORE_EXCEPTION_DETAIL

pytest also introduces new options to allow doctests to run in Python 2 and Python 3 unchanged:

  • ALLOW_UNICODE: when enabled, the u prefix is stripped from unicode strings in expected doctest output.
  • ALLOW_BYTES: when enabled, the b prefix is stripped from byte strings in expected doctest output.

As with any other option flag, these flags can be enabled in pytest.ini using the doctest_optionflags ini option:

[pytest]
doctest_optionflags = ALLOW_UNICODE ALLOW_BYTES

Alternatively, it can be enabled by an inline comment in the doc test itself:

# content of example.rst
>>> get_unicode_greeting()  # doctest: +ALLOW_UNICODE
'Hello'

The ‘doctest_namespace’ fixture

New in version 3.0.

The doctest_namespace fixture can be used to inject items into the namespace in which your doctests run. It is intended to be used within your own fixtures to provide the tests that use them with context.

doctest_namespace is a standard dict object into which you place the objects you want to appear in the doctest namespace:

# content of conftest.py
import numpy
@pytest.fixture(autouse=True)
def add_np(doctest_namespace):
    doctest_namespace['np'] = numpy

which can then be used in your doctests directly:

# content of numpy.py
def arange():
    """
    >>> a = np.arange(10)
    >>> len(a)
    10
    """
    pass

Output format

New in version 3.0.

You can change the diff output format on failure for your doctests by using one of standard doctest modules format in options (see doctest.REPORT_UDIFF, doctest.REPORT_CDIFF, doctest.REPORT_NDIFF, doctest.REPORT_ONLY_FIRST_FAILURE):

pytest --doctest-modules --doctest-report none
pytest --doctest-modules --doctest-report udiff
pytest --doctest-modules --doctest-report cdiff
pytest --doctest-modules --doctest-report ndiff
pytest --doctest-modules --doctest-report only_first_failure