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some fixes and clarifications to assert docs

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holger krekel 2011-06-18 22:30:46 +02:00
parent 4b4a2c8162
commit 8de50347fb
1 changed files with 16 additions and 10 deletions
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doc/assert.txt
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@ -19,7 +19,7 @@ following::
assert f() == 4 assert f() == 4
to assert that your function returns a certain value. If this assertion fails to assert that your function returns a certain value. If this assertion fails
you will see the value of ``x``:: you will see the return value of the function call::
$ py.test test_assert1.py $ py.test test_assert1.py
=========================== test session starts ============================ =========================== test session starts ============================
@ -40,16 +40,20 @@ you will see the value of ``x``::
========================= 1 failed in 0.02 seconds ========================= ========================= 1 failed in 0.02 seconds =========================
py.test has support for showing the values of the most common subexpressions py.test has support for showing the values of the most common subexpressions
including calls, attributes, comparisons, and binary and unary operators. This including calls, attributes, comparisons, and binary and unary
allows you to use the idiomatic python constructs without boilerplate code while operators. (See :ref:`tbreportdemo`). This allows you to use the
not losing introspection information. idiomatic python constructs without boilerplate code while not losing
introspection information.
Assertion introspection is enabled only when a message is not manually provided However, if you specify a message with the assertion like this::
in the assert statement.
assert a % 2 == 0, "value was odd, should be even"
then no assertion introspection takes places at all and the message
will be simply shown in the traceback.
See :ref:`assert-details` for more information on assertion introspection. See :ref:`assert-details` for more information on assertion introspection.
assertions about expected exceptions assertions about expected exceptions
------------------------------------------ ------------------------------------------
@ -139,15 +143,17 @@ Advanced assertion introspection
.. versionadded:: 2.1 .. versionadded:: 2.1
Reporting details about the failing assertion is achieved either by rewriting
Reporting details about a failing assertion is achieved either by rewriting
assert statements before they are run or re-evaluating the assert expression and assert statements before they are run or re-evaluating the assert expression and
recording the intermediate values. Which technique is used depends on the recording the intermediate values. Which technique is used depends on the
location of the assert, py.test's configuration, and Python version being used location of the assert, py.test's configuration, and Python version being used
to run py.test. to run py.test. However, for assert statements with a manually provided
message, i.e. ``assert expr, message``, no assertion introspection takes place and the manually provided message will be rendered in tracebacks.
By default, if the Python version is greater than or equal to 2.6, py.test By default, if the Python version is greater than or equal to 2.6, py.test
rewrites assert statements in test modules. Rewritten assert statements put rewrites assert statements in test modules. Rewritten assert statements put
introspection information into the assertion failure message. Note py.test only introspection information into the assertion failure message. py.test only
rewrites test modules directly discovered by its test collection process, so rewrites test modules directly discovered by its test collection process, so
asserts in supporting modules will not be rewritten. asserts in supporting modules will not be rewritten.