Source code for traits.testing.unittest_tools
# (C) Copyright 2005-2022 Enthought, Inc., Austin, TX
# All rights reserved.
#
# This software is provided without warranty under the terms of the BSD
# license included in LICENSE.txt and may be redistributed only under
# the conditions described in the aforementioned license. The license
# is also available online at http://www.enthought.com/licenses/BSD.txt
#
# Thanks for using Enthought open source!
""" Trait assert mixin class to simplify test implementation for Trait
Classes.
"""
import contextlib
import threading
import sys
import warnings
# Support for 'from traits.testing.unittest_tools import unittest',
# which was used to make unittest2 available under the name unittest
# on Python 2.6. We keep the import for now, for backwards compatibility.
import unittest # noqa: F401
from traits.api import (
Any,
Event,
HasStrictTraits,
Int,
List,
Str,
Property,
)
from traits.util.async_trait_wait import wait_for_condition
class _AssertTraitChangesContext(object):
""" A context manager used to implement the trait change assert methods.
Notes
-----
Checking if the provided xname corresponds to valid traits in the class
is not implemented yet.
Parameters
----------
obj : HasTraits
The HasTraits class instance whose class trait will change.
xname : str
The extended trait name of trait changes to listen to.
count : int, optional
The expected number of times the event should be fired. When None
(default value) there is no check for the number of times the
change event was fired.
test_case : TestCase
A unittest TestCase where to raise the failureException if
necessary.
Attributes
----------
obj : HasTraits
The HasTraits class instance whose class trait will change.
xname : str
The extended trait name of trait changes to listen to.
count : int, optional
The expected number of times the event should be fired. When None
(default value) there is no check for the number of times the
change event was fired.
events : list of tuples
A list with tuple elements containing the arguments of an
`on_trait_change` event signature (<object>, <name>, <old>, <new>).
Raises
------
AssertionError :
When the desired number of trait changed did not take place or when
`count = None` and no trait change took place.
"""
def __init__(self, obj, xname, count, test_case):
self.obj = obj
self.xname = xname
self.count = count
self.event = None
self.events = []
self.failureException = test_case.failureException
def _listener(self, obj, name, old, new):
""" Dummy trait listener.
"""
self.event = (obj, name, old, new)
self.events.append(self.event)
def __enter__(self):
""" Bind the trait listener.
"""
self.obj.on_trait_change(self._listener, self.xname)
return self
def __exit__(self, exc_type, exc_value, tb):
""" Remove the trait listener.
"""
if exc_type is not None:
return False
self.obj.on_trait_change(self._listener, self.xname, remove=True)
if self.count is not None and len(self.events) != self.count:
msg = "Change event for {0} was fired {1} times instead of {2}"
items = self.xname, len(self.events), self.count
raise self.failureException(msg.format(*items))
elif self.count is None and not self.events:
msg = "A change event was not fired for: {0}".format(self.xname)
raise self.failureException(msg)
return False
[docs]@contextlib.contextmanager
def reverse_assertion(context, msg):
context.__enter__()
try:
yield context
finally:
try:
context.__exit__(None, None, None)
except AssertionError:
pass
else:
raise context.failureException(msg)
class _TraitsChangeCollector(HasStrictTraits):
""" Class allowing thread-safe recording of events.
"""
# The object we're listening to.
obj = Any
# The (possibly extended) trait name(s).
trait_name = Str
# Read-only event count.
event_count = Property(Int)
# Event that's triggered when the event count is updated.
event_count_updated = Event
# Private list of events.
events = List(Any)
# Private lock used to allow access to events by multiple threads
# simultaneously.
_lock = Any()
def __init__(self, **traits):
if "trait" in traits:
value = traits.pop("trait")
message = (
"The `trait` keyword is deprecated." " please use `trait_name`"
)
warnings.warn(message, DeprecationWarning, stacklevel=2)
traits["trait_name"] = value
super().__init__(**traits)
# We assign the lock eagerly rather than depending on a lazy default,
# since we want to be sure that the lock is created (a) only once,
# and (b) on the main thread. Similarly for the events list.
self._lock = threading.Lock()
self.events = []
def start_collecting(self):
self.obj.on_trait_change(self._event_handler, self.trait_name)
def stop_collecting(self):
self.obj.on_trait_change(
self._event_handler, self.trait_name, remove=True
)
def _event_handler(self, new):
with self._lock:
self.events.append(new)
self.event_count_updated = True
def _get_event_count(self):
""" Traits property getter.
Thread-safe access to event count.
"""
with self._lock:
return len(self.events)
[docs]class UnittestTools(object):
""" Mixin class to augment the unittest.TestCase class with useful trait
related assert methods.
"""
[docs] def assertTraitChanges(
self, obj, trait, count=None, callableObj=None, *args, **kwargs
):
""" Assert an object trait changes a given number of times.
Assert that the class trait changes exactly `count` times during
execution of the provided function.
This method can also be used in a with statement to assert that
a class trait has changed during the execution of the code inside
the with statement (similar to the assertRaises method). Please note
that in that case the context manager returns itself and the user
can introspect the information of:
- The last event fired by accessing the ``event`` attribute of the
returned object.
- All the fired events by accessing the ``events`` attribute of
the return object.
Note that in the case of chained properties (trait 'foo' depends on
'bar', which in turn depends on 'baz'), the order in which the
corresponding trait events appear in the ``events`` attribute is
not well-defined, and may depend on dictionary ordering.
**Example**::
class MyClass(HasTraits):
number = Float(2.0)
my_class = MyClass()
with self.assertTraitChanges(my_class, 'number', count=1):
my_class.number = 3.0
Parameters
----------
obj : HasTraits
The HasTraits class instance whose class trait will change.
trait : str
The extended trait name of trait changes to listen to.
count : int or None, optional
The expected number of times the event should be fired. When None
(default value) there is no check for the number of times the
change event was fired.
callableObj : callable, optional
A callable object that will trigger the expected trait change.
When None (default value) a trigger is expected to be called
under the context manger returned by this method.
*args :
List of positional arguments for ``callableObj``
**kwargs :
Dict of keyword value pairs to be passed to the ``callableObj``
Returns
-------
context : context manager or None
If ``callableObj`` is None, an assertion context manager is
returned, inside of which a trait-change trigger can be invoked.
Otherwise, the context is used internally with ``callableObj`` as
the trigger, in which case None is returned.
Notes
-----
- Checking if the provided ``trait`` corresponds to valid traits in
the class is not implemented yet.
- Using the functional version of the assert method requires the
``count`` argument to be given even if it is None.
"""
context = _AssertTraitChangesContext(obj, trait, count, self)
if callableObj is None:
return context
with context:
callableObj(*args, **kwargs)
[docs] def assertTraitDoesNotChange(
self, obj, trait, callableObj=None, *args, **kwargs
):
""" Assert an object trait does not change.
Assert that the class trait does not change during
execution of the provided function.
Parameters
----------
obj : HasTraits
The HasTraits class instance whose class trait will change.
trait : str
The extended trait name of trait changes to listen to.
callableObj : callable, optional
A callable object that should not trigger a change in the
passed trait. When None (default value) a trigger is expected
to be called under the context manger returned by this method.
*args :
List of positional arguments for ``callableObj``
**kwargs :
Dict of keyword value pairs to be passed to the ``callableObj``
Returns
-------
context : context manager or None
If ``callableObj`` is None, an assertion context manager is
returned, inside of which a trait-change trigger can be invoked.
Otherwise, the context is used internally with ``callableObj`` as
the trigger, in which case None is returned.
"""
msg = "A change event was fired for: {0}".format(trait)
context = _AssertTraitChangesContext(obj, trait, None, self)
if callableObj is None:
return reverse_assertion(context, msg)
with reverse_assertion(context, msg):
callableObj(*args, **kwargs)
[docs] @contextlib.contextmanager
def assertMultiTraitChanges(
self, objects, traits_modified, traits_not_modified
):
""" Assert that traits on multiple objects do or do not change.
This combines some of the functionality of `assertTraitChanges` and
`assertTraitDoesNotChange`.
Parameters
----------
objects : list of HasTraits
The HasTraits class instances whose traits will change.
traits_modified : list of str
The extended trait names of trait expected to change.
traits_not_modified : list of str
The extended trait names of traits not expected to change.
"""
with contextlib.ExitStack() as exit_stack:
cms = []
for obj in objects:
for trait in traits_modified:
cms.append(exit_stack.enter_context(
self.assertTraitChanges(obj, trait)))
for trait in traits_not_modified:
cms.append(exit_stack.enter_context(
self.assertTraitDoesNotChange(obj, trait)))
yield tuple(cms)
[docs] @contextlib.contextmanager
def assertTraitChangesAsync(self, obj, trait, count=1, timeout=5.0):
""" Assert an object trait eventually changes.
Context manager used to assert that the given trait changes at
least `count` times within the given timeout, as a result of
execution of the body of the corresponding with block.
The trait changes are permitted to occur asynchronously.
**Example usage**::
with self.assertTraitChangesAsync(my_object, 'SomeEvent', count=4):
<do stuff that should cause my_object.SomeEvent to be
fired at least 4 times within the next 5 seconds>
Parameters
----------
obj : HasTraits
The HasTraits class instance whose class trait will change.
trait : str
The extended trait name of trait changes to listen to.
count : int, optional
The expected number of times the event should be fired.
timeout : float or None, optional
The amount of time in seconds to wait for the specified number
of changes. None can be used to indicate no timeout.
"""
collector = _TraitsChangeCollector(obj=obj, trait_name=trait)
# Pass control to body of the with statement.
collector.start_collecting()
try:
yield collector
# Wait for the expected number of events to arrive.
try:
wait_for_condition(
condition=lambda obj: obj.event_count >= count,
obj=collector,
trait="event_count_updated",
timeout=timeout,
)
except RuntimeError:
actual_event_count = collector.event_count
msg = (
"Expected {0} event on {1} to be fired at least {2} "
"times, but the event was only fired {3} times "
"before timeout ({4} seconds)."
).format(trait, obj, count, actual_event_count, timeout)
self.fail(msg)
finally:
collector.stop_collecting()
[docs] def assertEventuallyTrue(self, obj, trait, condition, timeout=5.0):
""" Assert that the given condition is eventually true.
Parameters
----------
obj : HasTraits
The HasTraits class instance whose traits will change.
trait : str
The extended trait name of trait changes to listen to.
condition : callable
A function that will be called when the specified trait
changes. This should accept ``obj`` and should return a
Boolean indicating whether the condition is satisfied or not.
timeout : float or None, optional
The amount of time in seconds to wait for the condition to
become true. None can be used to indicate no timeout.
"""
try:
wait_for_condition(
condition=condition, obj=obj, trait=trait, timeout=timeout
)
except RuntimeError:
# Helpful to know whether we timed out because the
# condition never became true, or because the expected
# event was never issued.
condition_at_timeout = condition(obj)
self.fail(
"Timed out waiting for condition. "
"At timeout, condition was {0}.".format(condition_at_timeout)
)
@contextlib.contextmanager
def _catch_warnings(self):
"""
Replacement for warnings.catch_warnings.
This method wraps warnings.catch_warnings, takes care to
reset the warning registry before entering the with context,
and ensures that DeprecationWarnings are always emitted.
The hack to reset the warning registry is no longer needed in
Python 3.4 and later. See http://bugs.python.org/issue4180 for
more background.
.. deprecated:: 6.2
Use :func:`warnings.catch_warnings` instead.
"""
warnings.warn(
(
"The _catch_warnings method is deprecated. "
"Use warnings.catch_warnings instead."
),
DeprecationWarning,
)
# Ugly hack copied from the core Python code (see
# Lib/test/test_support.py) to reset the warnings registry
# for the module making use of this context manager.
#
# Note that this hack is unnecessary in Python 3.4 and later; see
# http://bugs.python.org/issue4180 for the background.
registry = sys._getframe(4).f_globals.get("__warningregistry__")
if registry:
registry.clear()
with warnings.catch_warnings(record=True) as w:
warnings.simplefilter("always", DeprecationWarning)
yield w
[docs] @contextlib.contextmanager
def assertDeprecated(self):
"""
Assert that the code inside the with block is deprecated. Intended
for testing uses of traits.util.deprecated.deprecated.
"""
with warnings.catch_warnings(record=True) as w:
warnings.simplefilter("always", DeprecationWarning)
yield w
self.assertGreater(
len(w),
0,
msg="Expected a DeprecationWarning, " "but none was issued",
)
[docs] @contextlib.contextmanager
def assertNotDeprecated(self):
"""
Assert that the code inside the with block is not deprecated. Intended
for testing uses of traits.util.deprecated.deprecated.
"""
with warnings.catch_warnings(record=True) as w:
warnings.simplefilter("always", DeprecationWarning)
yield w
self.assertEqual(
len(w),
0,
msg="Expected no DeprecationWarning, "
"but at least one was issued",
)
