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Remove `raises` and `approx` from `python.py`. 

These two classes were recently moved to `python_api.py`, but it seems
that they found their way back into the original file somehow.  This
commit removes them again to avoid out-of-date code duplication.
This commit is contained in:
Kale Kundert 2017-07-22 08:36:15 -07:00
parent 6461dc9fc6
commit a3b35e1c4b
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@ -1096,438 +1096,6 @@ def write_docstring(tw, doc):
tw.write(INDENT + line + "\n") tw.write(INDENT + line + "\n")
# builtin pytest.raises helper
def raises(expected_exception, *args, **kwargs):
"""
Assert that a code block/function call raises ``expected_exception``
and raise a failure exception otherwise.
This helper produces a ``ExceptionInfo()`` object (see below).
If using Python 2.5 or above, you may use this function as a
context manager::
>>> with raises(ZeroDivisionError):
... 1/0
.. versionchanged:: 2.10
In the context manager form you may use the keyword argument
``message`` to specify a custom failure message::
>>> with raises(ZeroDivisionError, message="Expecting ZeroDivisionError"):
... pass
Traceback (most recent call last):
...
Failed: Expecting ZeroDivisionError
.. note::
When using ``pytest.raises`` as a context manager, it's worthwhile to
note that normal context manager rules apply and that the exception
raised *must* be the final line in the scope of the context manager.
Lines of code after that, within the scope of the context manager will
not be executed. For example::
>>> value = 15
>>> with raises(ValueError) as exc_info:
... if value > 10:
... raise ValueError("value must be <= 10")
... assert exc_info.type == ValueError # this will not execute
Instead, the following approach must be taken (note the difference in
scope)::
>>> with raises(ValueError) as exc_info:
... if value > 10:
... raise ValueError("value must be <= 10")
...
>>> assert exc_info.type == ValueError
Or you can use the keyword argument ``match`` to assert that the
exception matches a text or regex::
>>> with raises(ValueError, match='must be 0 or None'):
... raise ValueError("value must be 0 or None")
>>> with raises(ValueError, match=r'must be \d+$'):
... raise ValueError("value must be 42")
Or you can specify a callable by passing a to-be-called lambda::
>>> raises(ZeroDivisionError, lambda: 1/0)
<ExceptionInfo ...>
or you can specify an arbitrary callable with arguments::
>>> def f(x): return 1/x
...
>>> raises(ZeroDivisionError, f, 0)
<ExceptionInfo ...>
>>> raises(ZeroDivisionError, f, x=0)
<ExceptionInfo ...>
A third possibility is to use a string to be executed::
>>> raises(ZeroDivisionError, "f(0)")
<ExceptionInfo ...>
.. autoclass:: _pytest._code.ExceptionInfo
:members:
.. note::
Similar to caught exception objects in Python, explicitly clearing
local references to returned ``ExceptionInfo`` objects can
help the Python interpreter speed up its garbage collection.
Clearing those references breaks a reference cycle
(``ExceptionInfo`` --> caught exception --> frame stack raising
the exception --> current frame stack --> local variables -->
``ExceptionInfo``) which makes Python keep all objects referenced
from that cycle (including all local variables in the current
frame) alive until the next cyclic garbage collection run. See the
official Python ``try`` statement documentation for more detailed
information.
"""
__tracebackhide__ = True
msg = ("exceptions must be old-style classes or"
" derived from BaseException, not %s")
if isinstance(expected_exception, tuple):
for exc in expected_exception:
if not isclass(exc):
raise TypeError(msg % type(exc))
elif not isclass(expected_exception):
raise TypeError(msg % type(expected_exception))
message = "DID NOT RAISE {0}".format(expected_exception)
match_expr = None
if not args:
if "message" in kwargs:
message = kwargs.pop("message")
if "match" in kwargs:
match_expr = kwargs.pop("match")
message += " matching '{0}'".format(match_expr)
return RaisesContext(expected_exception, message, match_expr)
elif isinstance(args[0], str):
code, = args
assert isinstance(code, str)
frame = sys._getframe(1)
loc = frame.f_locals.copy()
loc.update(kwargs)
# print "raises frame scope: %r" % frame.f_locals
try:
code = _pytest._code.Source(code).compile()
py.builtin.exec_(code, frame.f_globals, loc)
# XXX didn'T mean f_globals == f_locals something special?
# this is destroyed here ...
except expected_exception:
return _pytest._code.ExceptionInfo()
else:
func = args[0]
try:
func(*args[1:], **kwargs)
except expected_exception:
return _pytest._code.ExceptionInfo()
fail(message)
raises.Exception = fail.Exception
class RaisesContext(object):
def __init__(self, expected_exception, message, match_expr):
self.expected_exception = expected_exception
self.message = message
self.match_expr = match_expr
self.excinfo = None
def __enter__(self):
self.excinfo = object.__new__(_pytest._code.ExceptionInfo)
return self.excinfo
def __exit__(self, *tp):
__tracebackhide__ = True
if tp[0] is None:
fail(self.message)
if sys.version_info < (2, 7):
# py26: on __exit__() exc_value often does not contain the
# exception value.
# http://bugs.python.org/issue7853
if not isinstance(tp[1], BaseException):
exc_type, value, traceback = tp
tp = exc_type, exc_type(value), traceback
self.excinfo.__init__(tp)
suppress_exception = issubclass(self.excinfo.type, self.expected_exception)
if sys.version_info[0] == 2 and suppress_exception:
sys.exc_clear()
if self.match_expr:
self.excinfo.match(self.match_expr)
return suppress_exception
# builtin pytest.approx helper
class approx(object):
"""
Assert that two numbers (or two sets of numbers) are equal to each other
within some tolerance.
Due to the `intricacies of floating-point arithmetic`__, numbers that we
would intuitively expect to be equal are not always so::
>>> 0.1 + 0.2 == 0.3
False
__ https://docs.python.org/3/tutorial/floatingpoint.html
This problem is commonly encountered when writing tests, e.g. when making
sure that floating-point values are what you expect them to be. One way to
deal with this problem is to assert that two floating-point numbers are
equal to within some appropriate tolerance::
>>> abs((0.1 + 0.2) - 0.3) < 1e-6
True
However, comparisons like this are tedious to write and difficult to
understand. Furthermore, absolute comparisons like the one above are
usually discouraged because there's no tolerance that works well for all
situations. ``1e-6`` is good for numbers around ``1``, but too small for
very big numbers and too big for very small ones. It's better to express
the tolerance as a fraction of the expected value, but relative comparisons
like that are even more difficult to write correctly and concisely.
The ``approx`` class performs floating-point comparisons using a syntax
that's as intuitive as possible::
>>> from pytest import approx
>>> 0.1 + 0.2 == approx(0.3)
True
The same syntax also works on sequences of numbers::
>>> (0.1 + 0.2, 0.2 + 0.4) == approx((0.3, 0.6))
True
By default, ``approx`` considers numbers within a relative tolerance of
``1e-6`` (i.e. one part in a million) of its expected value to be equal.
This treatment would lead to surprising results if the expected value was
``0.0``, because nothing but ``0.0`` itself is relatively close to ``0.0``.
To handle this case less surprisingly, ``approx`` also considers numbers
within an absolute tolerance of ``1e-12`` of its expected value to be
equal. Infinite numbers are another special case. They are only
considered equal to themselves, regardless of the relative tolerance. Both
the relative and absolute tolerances can be changed by passing arguments to
the ``approx`` constructor::
>>> 1.0001 == approx(1)
False
>>> 1.0001 == approx(1, rel=1e-3)
True
>>> 1.0001 == approx(1, abs=1e-3)
True
If you specify ``abs`` but not ``rel``, the comparison will not consider
the relative tolerance at all. In other words, two numbers that are within
the default relative tolerance of ``1e-6`` will still be considered unequal
if they exceed the specified absolute tolerance. If you specify both
``abs`` and ``rel``, the numbers will be considered equal if either
tolerance is met::
>>> 1 + 1e-8 == approx(1)
True
>>> 1 + 1e-8 == approx(1, abs=1e-12)
False
>>> 1 + 1e-8 == approx(1, rel=1e-6, abs=1e-12)
True
If you're thinking about using ``approx``, then you might want to know how
it compares to other good ways of comparing floating-point numbers. All of
these algorithms are based on relative and absolute tolerances and should
agree for the most part, but they do have meaningful differences:
- ``math.isclose(a, b, rel_tol=1e-9, abs_tol=0.0)``: True if the relative
tolerance is met w.r.t. either ``a`` or ``b`` or if the absolute
tolerance is met. Because the relative tolerance is calculated w.r.t.
both ``a`` and ``b``, this test is symmetric (i.e. neither ``a`` nor
``b`` is a "reference value"). You have to specify an absolute tolerance
if you want to compare to ``0.0`` because there is no tolerance by
default. Only available in python>=3.5. `More information...`__
__ https://docs.python.org/3/library/math.html#math.isclose
- ``numpy.isclose(a, b, rtol=1e-5, atol=1e-8)``: True if the difference
between ``a`` and ``b`` is less that the sum of the relative tolerance
w.r.t. ``b`` and the absolute tolerance. Because the relative tolerance
is only calculated w.r.t. ``b``, this test is asymmetric and you can
think of ``b`` as the reference value. Support for comparing sequences
is provided by ``numpy.allclose``. `More information...`__
__ http://docs.scipy.org/doc/numpy-1.10.0/reference/generated/numpy.isclose.html
- ``unittest.TestCase.assertAlmostEqual(a, b)``: True if ``a`` and ``b``
are within an absolute tolerance of ``1e-7``. No relative tolerance is
considered and the absolute tolerance cannot be changed, so this function
is not appropriate for very large or very small numbers. Also, it's only
available in subclasses of ``unittest.TestCase`` and it's ugly because it
doesn't follow PEP8. `More information...`__
__ https://docs.python.org/3/library/unittest.html#unittest.TestCase.assertAlmostEqual
- ``a == pytest.approx(b, rel=1e-6, abs=1e-12)``: True if the relative
tolerance is met w.r.t. ``b`` or if the absolute tolerance is met.
Because the relative tolerance is only calculated w.r.t. ``b``, this test
is asymmetric and you can think of ``b`` as the reference value. In the
special case that you explicitly specify an absolute tolerance but not a
relative tolerance, only the absolute tolerance is considered.
"""
def __init__(self, expected, rel=None, abs=None):
self.expected = expected
self.abs = abs
self.rel = rel
def __repr__(self):
return ', '.join(repr(x) for x in self.expected)
def __eq__(self, actual):
from collections import Iterable
if not isinstance(actual, Iterable):
actual = [actual]
if len(actual) != len(self.expected):
return False
return all(a == x for a, x in zip(actual, self.expected))
__hash__ = None
def __ne__(self, actual):
return not (actual == self)
@property
def expected(self):
# Regardless of whether the user-specified expected value is a number
# or a sequence of numbers, return a list of ApproxNotIterable objects
# that can be compared against.
from collections import Iterable
def approx_non_iter(x):
return ApproxNonIterable(x, self.rel, self.abs)
if isinstance(self._expected, Iterable):
return [approx_non_iter(x) for x in self._expected]
else:
return [approx_non_iter(self._expected)]
@expected.setter
def expected(self, expected):
self._expected = expected
class ApproxNonIterable(object):
"""
Perform approximate comparisons for single numbers only.
In other words, the ``expected`` attribute for objects of this class must
be some sort of number. This is in contrast to the ``approx`` class, where
the ``expected`` attribute can either be a number of a sequence of numbers.
This class is responsible for making comparisons, while ``approx`` is
responsible for abstracting the difference between numbers and sequences of
numbers. Although this class can stand on its own, it's only meant to be
used within ``approx``.
"""
def __init__(self, expected, rel=None, abs=None):
self.expected = expected
self.abs = abs
self.rel = rel
def __repr__(self):
if isinstance(self.expected, complex):
return str(self.expected)
# Infinities aren't compared using tolerances, so don't show a
# tolerance.
if math.isinf(self.expected):
return str(self.expected)
# If a sensible tolerance can't be calculated, self.tolerance will
# raise a ValueError. In this case, display '???'.
try:
vetted_tolerance = '{:.1e}'.format(self.tolerance)
except ValueError:
vetted_tolerance = '???'
if sys.version_info[0] == 2:
return '{0} +- {1}'.format(self.expected, vetted_tolerance)
else:
return u'{0} \u00b1 {1}'.format(self.expected, vetted_tolerance)
def __eq__(self, actual):
# Short-circuit exact equality.
if actual == self.expected:
return True
# Infinity shouldn't be approximately equal to anything but itself, but
# if there's a relative tolerance, it will be infinite and infinity
# will seem approximately equal to everything. The equal-to-itself
# case would have been short circuited above, so here we can just
# return false if the expected value is infinite. The abs() call is
# for compatibility with complex numbers.
if math.isinf(abs(self.expected)):
return False
# Return true if the two numbers are within the tolerance.
return abs(self.expected - actual) <= self.tolerance
__hash__ = None
def __ne__(self, actual):
return not (actual == self)
@property
def tolerance(self):
def set_default(x, default):
return x if x is not None else default
# Figure out what the absolute tolerance should be. ``self.abs`` is
# either None or a value specified by the user.
absolute_tolerance = set_default(self.abs, 1e-12)
if absolute_tolerance < 0:
raise ValueError("absolute tolerance can't be negative: {}".format(absolute_tolerance))
if math.isnan(absolute_tolerance):
raise ValueError("absolute tolerance can't be NaN.")
# If the user specified an absolute tolerance but not a relative one,
# just return the absolute tolerance.
if self.rel is None:
if self.abs is not None:
return absolute_tolerance
# Figure out what the relative tolerance should be. ``self.rel`` is
# either None or a value specified by the user. This is done after
# we've made sure the user didn't ask for an absolute tolerance only,
# because we don't want to raise errors about the relative tolerance if
# we aren't even going to use it.
relative_tolerance = set_default(self.rel, 1e-6) * abs(self.expected)
if relative_tolerance < 0:
raise ValueError("relative tolerance can't be negative: {}".format(absolute_tolerance))
if math.isnan(relative_tolerance):
raise ValueError("relative tolerance can't be NaN.")
# Return the larger of the relative and absolute tolerances.
return max(relative_tolerance, absolute_tolerance)
#
# the basic pytest Function item
#
class Function(FunctionMixin, main.Item, fixtures.FuncargnamesCompatAttr): class Function(FunctionMixin, main.Item, fixtures.FuncargnamesCompatAttr):
""" a Function Item is responsible for setting up and executing a """ a Function Item is responsible for setting up and executing a
Python test function. Python test function.