twisted/test/test_monkey.py

   1 # Copyright (c) Twisted Matrix Laboratories.
   2 # See LICENSE for details.
   3
   4 """
   5 Tests for L{twisted.python.monkey}.
   6 """
   7
   8 from twisted.trial import unittest
   9 from twisted.python.monkey import MonkeyPatcher
  10
  11
  12 class TestObj:
  13     def __init__(self):
  14         self.foo = 'foo value'
  15         self.bar = 'bar value'
  16         self.baz = 'baz value'
  17
  18
  19 class MonkeyPatcherTest(unittest.TestCase):
  20     """
  21     Tests for L{MonkeyPatcher} monkey-patching class.
  22     """
  23
  24     def setUp(self):
  25         self.testObject = TestObj()
  26         self.originalObject = TestObj()
  27         self.monkeyPatcher = MonkeyPatcher()
  28
  29
  30     def test_empty(self):
  31         """
  32         A monkey patcher without patches shouldn't change a thing.
  33         """
  34         self.monkeyPatcher.patch()
  35
  36         # We can't assert that all state is unchanged, but at least we can
  37         # check our test object.
  38         self.assertEqual(self.originalObject.foo, self.testObject.foo)
  39         self.assertEqual(self.originalObject.bar, self.testObject.bar)
  40         self.assertEqual(self.originalObject.baz, self.testObject.baz)
  41
  42
  43     def test_constructWithPatches(self):
  44         """
  45         Constructing a L{MonkeyPatcher} with patches should add all of the
  46         given patches to the patch list.
  47         """
  48         patcher = MonkeyPatcher((self.testObject, 'foo', 'haha'),
  49                                 (self.testObject, 'bar', 'hehe'))
  50         patcher.patch()
  51         self.assertEqual('haha', self.testObject.foo)
  52         self.assertEqual('hehe', self.testObject.bar)
  53         self.assertEqual(self.originalObject.baz, self.testObject.baz)
  54
  55
  56     def test_patchExisting(self):
  57         """
  58         Patching an attribute that exists sets it to the value defined in the
  59         patch.
  60         """
  61         self.monkeyPatcher.addPatch(self.testObject, 'foo', 'haha')
  62         self.monkeyPatcher.patch()
  63         self.assertEqual(self.testObject.foo, 'haha')
  64
  65
  66     def test_patchNonExisting(self):
  67         """
  68         Patching a non-existing attribute fails with an C{AttributeError}.
  69         """
  70         self.monkeyPatcher.addPatch(self.testObject, 'nowhere',
  71                                     'blow up please')
  72         self.assertRaises(AttributeError, self.monkeyPatcher.patch)
  73
  74
  75     def test_patchAlreadyPatched(self):
  76         """
  77         Adding a patch for an object and attribute that already have a patch
  78         overrides the existing patch.
  79         """
  80         self.monkeyPatcher.addPatch(self.testObject, 'foo', 'blah')
  81         self.monkeyPatcher.addPatch(self.testObject, 'foo', 'BLAH')
  82         self.monkeyPatcher.patch()
  83         self.assertEqual(self.testObject.foo, 'BLAH')
  84         self.monkeyPatcher.restore()
  85         self.assertEqual(self.testObject.foo, self.originalObject.foo)
  86
  87
  88     def test_restoreTwiceIsANoOp(self):
  89         """
  90         Restoring an already-restored monkey patch is a no-op.
  91         """
  92         self.monkeyPatcher.addPatch(self.testObject, 'foo', 'blah')
  93         self.monkeyPatcher.patch()
  94         self.monkeyPatcher.restore()
  95         self.assertEqual(self.testObject.foo, self.originalObject.foo)
  96         self.monkeyPatcher.restore()
  97         self.assertEqual(self.testObject.foo, self.originalObject.foo)
  98
  99
 100     def test_runWithPatchesDecoration(self):
 101         """
 102         runWithPatches should run the given callable, passing in all arguments
 103         and keyword arguments, and return the return value of the callable.
 104         """
 105         log = []
 106
 107         def f(a, b, c=None):
 108             log.append((a, b, c))
 109             return 'foo'
 110
 111         result = self.monkeyPatcher.runWithPatches(f, 1, 2, c=10)
 112         self.assertEqual('foo', result)
 113         self.assertEqual([(1, 2, 10)], log)
 114
 115
 116     def test_repeatedRunWithPatches(self):
 117         """
 118         We should be able to call the same function with runWithPatches more
 119         than once. All patches should apply for each call.
 120         """
 121         def f():
 122             return (self.testObject.foo, self.testObject.bar,
 123                     self.testObject.baz)
 124
 125         self.monkeyPatcher.addPatch(self.testObject, 'foo', 'haha')
 126         result = self.monkeyPatcher.runWithPatches(f)
 127         self.assertEqual(
 128             ('haha', self.originalObject.bar, self.originalObject.baz), result)
 129         result = self.monkeyPatcher.runWithPatches(f)
 130         self.assertEqual(
 131             ('haha', self.originalObject.bar, self.originalObject.baz),
 132             result)
 133
 134
 135     def test_runWithPatchesRestores(self):
 136         """
 137         C{runWithPatches} should restore the original values after the function
 138         has executed.
 139         """
 140         self.monkeyPatcher.addPatch(self.testObject, 'foo', 'haha')
 141         self.assertEqual(self.originalObject.foo, self.testObject.foo)
 142         self.monkeyPatcher.runWithPatches(lambda: None)
 143         self.assertEqual(self.originalObject.foo, self.testObject.foo)
 144
 145
 146     def test_runWithPatchesRestoresOnException(self):
 147         """
 148         Test runWithPatches restores the original values even when the function
 149         raises an exception.
 150         """
 151         def _():
 152             self.assertEqual(self.testObject.foo, 'haha')
 153             self.assertEqual(self.testObject.bar, 'blahblah')
 154             raise RuntimeError, "Something went wrong!"
 155
 156         self.monkeyPatcher.addPatch(self.testObject, 'foo', 'haha')
 157         self.monkeyPatcher.addPatch(self.testObject, 'bar', 'blahblah')
 158
 159         self.assertRaises(RuntimeError, self.monkeyPatcher.runWithPatches, _)
 160         self.assertEqual(self.testObject.foo, self.originalObject.foo)
 161         self.assertEqual(self.testObject.bar, self.originalObject.bar)