Issue 5354: Provide a standardised testing mechanism for doing fresh imports of modules, including the ability to block extension modules in order to test the pure Python fallbacks
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@ -339,6 +339,30 @@ The :mod:`test.test_support` module defines the following functions:
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.. versionadded:: 2.6
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.. function:: import_module(name, deprecated=False)
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This function imports and returns the named module. Unlike a normal
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import, this function raises :exc:`unittest.SkipTest` if the module
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cannot be imported.
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Module and package deprecation messages are suppressed during this import
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if *deprecated* is :const:`True`.
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.. versionadded:: 2.7
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.. function:: import_fresh_module(name, blocked_names=None, deprecated=False)
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This function imports and returns a fresh copy of the named Python module. The
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``sys.modules`` cache is bypassed temporarily, and the ability to import the
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modules named in *blocked_names* is suppressed for the duration of the import.
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Module and package deprecation messages are suppressed during this import
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if *deprecated* is :const:`True`.
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.. versionadded:: 2.7
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The :mod:`test.test_support` module defines the following classes:
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.. class:: TransientResource(exc[, **kwargs])
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@ -7,23 +7,8 @@ import sys
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# We do a bit of trickery here to be able to test both the C implementation
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# and the Python implementation of the module.
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# Make it impossible to import the C implementation anymore.
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sys.modules['_heapq'] = 0
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# We must also handle the case that heapq was imported before.
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if 'heapq' in sys.modules:
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del sys.modules['heapq']
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# Now we can import the module and get the pure Python implementation.
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import heapq as py_heapq
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# Restore everything to normal.
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del sys.modules['_heapq']
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del sys.modules['heapq']
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# This is now the module with the C implementation.
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import heapq as c_heapq
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py_heapq = test_support.import_fresh_module('heapq', ['_heapq'])
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class TestHeap(unittest.TestCase):
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module = None
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@ -193,6 +178,13 @@ class TestHeap(unittest.TestCase):
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class TestHeapPython(TestHeap):
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module = py_heapq
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# As an early adopter, we sanity check the
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# test_support.import_fresh_module utility function
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def test_pure_python(self):
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self.assertFalse(sys.modules['heapq'] is self.module)
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self.assertTrue(hasattr(self.module.heapify, 'func_code'))
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class TestHeapC(TestHeap):
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module = c_heapq
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@ -217,6 +209,12 @@ class TestHeapC(TestHeap):
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self.assertEqual(hsort(data, LT), target)
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self.assertEqual(hsort(data, LE), target)
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# As an early adopter, we sanity check the
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# test_support.import_fresh_module utility function
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def test_accelerated(self):
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self.assertTrue(sys.modules['heapq'] is self.module)
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self.assertFalse(hasattr(self.module.heapify, 'func_code'))
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#==============================================================================
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@ -42,22 +42,63 @@ class ResourceDenied(unittest.SkipTest):
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and unexpected skips.
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"""
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@contextlib.contextmanager
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def _ignore_deprecated_imports(ignore=True):
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"""Context manager to suppress package and module deprecation
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warnings when importing them.
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If ignore is False, this context manager has no effect."""
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if ignore:
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with warnings.catch_warnings():
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warnings.filterwarnings("ignore", ".+ (module|package)",
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DeprecationWarning)
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yield
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else:
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yield
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def import_module(name, deprecated=False):
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"""Import and return the module to be tested, raising SkipTest if
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it is not available.
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If deprecated is True, any module or package deprecation messages
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will be suppressed."""
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with warnings.catch_warnings():
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if deprecated:
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warnings.filterwarnings("ignore", ".+ (module|package)",
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DeprecationWarning)
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with _ignore_deprecated_imports(deprecated):
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try:
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module = importlib.import_module(name)
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return importlib.import_module(name)
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except ImportError, msg:
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raise unittest.SkipTest(str(msg))
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else:
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return module
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def import_fresh_module(name, blocked_names=None, deprecated=False):
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"""Imports and returns a module, deliberately bypassing the sys.modules cache
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and importing a fresh copy of the module. Once the import is complete,
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the sys.modules cache is restored to its original state.
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Importing of modules named in blocked_names is prevented while the fresh import
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takes place.
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If deprecated is True, any module or package deprecation messages
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will be suppressed."""
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# NOTE: test_heapq and test_warnings include extra sanity checks to make
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# sure that this utility function is working as expected
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with _ignore_deprecated_imports(deprecated):
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if blocked_names is None:
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blocked_names = ()
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orig_modules = {}
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if name in sys.modules:
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orig_modules[name] = sys.modules[name]
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del sys.modules[name]
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try:
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for blocked in blocked_names:
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orig_modules[blocked] = sys.modules[blocked]
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sys.modules[blocked] = 0
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py_module = importlib.import_module(name)
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finally:
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for blocked, module in orig_modules.items():
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sys.modules[blocked] = module
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return py_module
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def get_attribute(obj, name):
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"""Get an attribute, raising SkipTest if AttributeError is raised."""
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@ -10,18 +10,8 @@ import warning_tests
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import warnings as original_warnings
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sys.modules['_warnings'] = 0
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del sys.modules['warnings']
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import warnings as py_warnings
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del sys.modules['_warnings']
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del sys.modules['warnings']
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import warnings as c_warnings
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sys.modules['warnings'] = original_warnings
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py_warnings = test_support.import_fresh_module('warnings', ['_warnings'])
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c_warnings = test_support.import_fresh_module('warnings')
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@contextmanager
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def warnings_state(module):
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@ -341,9 +331,21 @@ class WarnTests(unittest.TestCase):
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class CWarnTests(BaseTest, WarnTests):
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module = c_warnings
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# As an early adopter, we sanity check the
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# test_support.import_fresh_module utility function
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def test_accelerated(self):
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self.assertFalse(original_warnings is self.module)
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self.assertFalse(hasattr(self.module.warn, 'func_code'))
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class PyWarnTests(BaseTest, WarnTests):
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module = py_warnings
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# As an early adopter, we sanity check the
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# test_support.import_fresh_module utility function
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def test_pure_python(self):
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self.assertFalse(original_warnings is self.module)
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self.assertTrue(hasattr(self.module.warn, 'func_code'))
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class WCmdLineTests(unittest.TestCase):
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