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185 lines
6.9 KiB
185 lines
6.9 KiB
2 years ago
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import unittest
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import builtins
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import os
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from platform import system as platform_system
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class ExceptionClassTests(unittest.TestCase):
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"""Tests for anything relating to exception objects themselves (e.g.,
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inheritance hierarchy)"""
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def test_builtins_new_style(self):
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self.assertTrue(issubclass(Exception, object))
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def verify_instance_interface(self, ins):
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for attr in ("args", "__str__", "__repr__"):
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self.assertTrue(hasattr(ins, attr),
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"%s missing %s attribute" %
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(ins.__class__.__name__, attr))
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def test_inheritance(self):
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# Make sure the inheritance hierarchy matches the documentation
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exc_set = set()
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for object_ in builtins.__dict__.values():
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try:
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if issubclass(object_, BaseException):
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exc_set.add(object_.__name__)
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except TypeError:
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pass
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inheritance_tree = open(
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os.path.join(os.path.split(__file__)[0], 'exception_hierarchy.txt'),
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encoding="utf-8")
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try:
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superclass_name = inheritance_tree.readline().rstrip()
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try:
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last_exc = getattr(builtins, superclass_name)
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except AttributeError:
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self.fail("base class %s not a built-in" % superclass_name)
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self.assertIn(superclass_name, exc_set,
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'%s not found' % superclass_name)
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exc_set.discard(superclass_name)
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superclasses = [] # Loop will insert base exception
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last_depth = 0
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for exc_line in inheritance_tree:
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exc_line = exc_line.rstrip()
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depth = exc_line.rindex('-')
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exc_name = exc_line[depth+2:] # Slice past space
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if '(' in exc_name:
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paren_index = exc_name.index('(')
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platform_name = exc_name[paren_index+1:-1]
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exc_name = exc_name[:paren_index-1] # Slice off space
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if platform_system() != platform_name:
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exc_set.discard(exc_name)
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continue
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if '[' in exc_name:
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left_bracket = exc_name.index('[')
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exc_name = exc_name[:left_bracket-1] # cover space
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try:
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exc = getattr(builtins, exc_name)
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except AttributeError:
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self.fail("%s not a built-in exception" % exc_name)
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if last_depth < depth:
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superclasses.append((last_depth, last_exc))
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elif last_depth > depth:
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while superclasses[-1][0] >= depth:
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superclasses.pop()
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self.assertTrue(issubclass(exc, superclasses[-1][1]),
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"%s is not a subclass of %s" % (exc.__name__,
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superclasses[-1][1].__name__))
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try: # Some exceptions require arguments; just skip them
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self.verify_instance_interface(exc())
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except TypeError:
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pass
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self.assertIn(exc_name, exc_set)
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exc_set.discard(exc_name)
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last_exc = exc
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last_depth = depth
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finally:
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inheritance_tree.close()
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self.assertEqual(len(exc_set), 0, "%s not accounted for" % exc_set)
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interface_tests = ("length", "args", "str", "repr")
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def interface_test_driver(self, results):
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for test_name, (given, expected) in zip(self.interface_tests, results):
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self.assertEqual(given, expected, "%s: %s != %s" % (test_name,
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given, expected))
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def test_interface_single_arg(self):
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# Make sure interface works properly when given a single argument
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arg = "spam"
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exc = Exception(arg)
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results = ([len(exc.args), 1], [exc.args[0], arg],
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[str(exc), str(arg)],
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[repr(exc), '%s(%r)' % (exc.__class__.__name__, arg)])
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self.interface_test_driver(results)
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def test_interface_multi_arg(self):
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# Make sure interface correct when multiple arguments given
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arg_count = 3
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args = tuple(range(arg_count))
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exc = Exception(*args)
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results = ([len(exc.args), arg_count], [exc.args, args],
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[str(exc), str(args)],
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[repr(exc), exc.__class__.__name__ + repr(exc.args)])
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self.interface_test_driver(results)
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def test_interface_no_arg(self):
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# Make sure that with no args that interface is correct
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exc = Exception()
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results = ([len(exc.args), 0], [exc.args, tuple()],
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[str(exc), ''],
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[repr(exc), exc.__class__.__name__ + '()'])
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self.interface_test_driver(results)
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class UsageTests(unittest.TestCase):
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"""Test usage of exceptions"""
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def raise_fails(self, object_):
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"""Make sure that raising 'object_' triggers a TypeError."""
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try:
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raise object_
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except TypeError:
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return # What is expected.
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self.fail("TypeError expected for raising %s" % type(object_))
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def catch_fails(self, object_):
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"""Catching 'object_' should raise a TypeError."""
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try:
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try:
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raise Exception
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except object_:
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pass
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except TypeError:
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pass
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except Exception:
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self.fail("TypeError expected when catching %s" % type(object_))
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try:
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try:
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raise Exception
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except (object_,):
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pass
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except TypeError:
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return
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except Exception:
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self.fail("TypeError expected when catching %s as specified in a "
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"tuple" % type(object_))
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def test_raise_new_style_non_exception(self):
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# You cannot raise a new-style class that does not inherit from
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# BaseException; the ability was not possible until BaseException's
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# introduction so no need to support new-style objects that do not
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# inherit from it.
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class NewStyleClass(object):
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pass
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self.raise_fails(NewStyleClass)
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self.raise_fails(NewStyleClass())
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def test_raise_string(self):
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# Raising a string raises TypeError.
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self.raise_fails("spam")
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def test_catch_non_BaseException(self):
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# Trying to catch an object that does not inherit from BaseException
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# is not allowed.
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class NonBaseException(object):
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pass
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self.catch_fails(NonBaseException)
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self.catch_fails(NonBaseException())
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def test_catch_BaseException_instance(self):
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# Catching an instance of a BaseException subclass won't work.
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self.catch_fails(BaseException())
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def test_catch_string(self):
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# Catching a string is bad.
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self.catch_fails("spam")
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if __name__ == '__main__':
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unittest.main()
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