Mock 100% coverage (GH-13045)

This was achieved by:
* moving many pass statements in tests onto their own lines, so they pass line coverage and can match an easy ignore pattern if branch coverage is added later.
* removing code that cannot be reached.
* removing long-disabled tests.
* removing unused code.
* adding tests for uncovered code

It turned out that removing `if __name__ == '__main__'` blocks that run unittest.main() at the bottom of test files was surprisingly contentious, so they remain and can be filtered out with an appropriate .coveragerc.

Lib/unittest/mock.py

@@ -63,10 +63,7 @@ def _get_signature_object(func, as_instance, eat_self):
     """
     if isinstance(func, type) and not as_instance:
         # If it's a type and should be modelled as a type, use __init__.
-        try:
-            func = func.__init__
-        except AttributeError:
-            return None
+        func = func.__init__
         # Skip the `self` argument in __init__
         eat_self = True
     elif not isinstance(func, FunctionTypes):
@@ -147,8 +144,6 @@ def _set_signature(mock, original, instance=False):
     # creates a function with signature (*args, **kwargs) that delegates to a
     # mock. It still does signature checking by calling a lambda with the same
     # signature as the original.
-    if not _callable(original):
-        return
 
     skipfirst = isinstance(original, type)
     result = _get_signature_object(original, instance, skipfirst)
@@ -175,10 +170,6 @@ def _set_signature(mock, original, instance=False):
 def _setup_func(funcopy, mock, sig):
     funcopy.mock = mock
 
-    # can't use isinstance with mocks
-    if not _is_instance_mock(mock):
-        return
-
     def assert_called_with(*args, **kwargs):
         return mock.assert_called_with(*args, **kwargs)
     def assert_called(*args, **kwargs):
@@ -263,12 +254,6 @@ _missing = sentinel.MISSING
 _deleted = sentinel.DELETED
 
 
-def _copy(value):
-    if type(value) in (dict, list, tuple, set):
-        return type(value)(value)
-    return value
-
-
 _allowed_names = {
     'return_value', '_mock_return_value', 'side_effect',
     '_mock_side_effect', '_mock_parent', '_mock_new_parent',
@@ -351,8 +336,6 @@ def _check_and_set_parent(parent, value, name, new_name):
 class _MockIter(object):
     def __init__(self, obj):
         self.obj = iter(obj)
-    def __iter__(self):
-        return self
     def __next__(self):
         return next(self.obj)
 
@@ -452,7 +435,7 @@ class NonCallableMock(Base):
             if isinstance(spec, type):
                 _spec_class = spec
             else:
-                _spec_class = _get_class(spec)
+                _spec_class = type(spec)
             res = _get_signature_object(spec,
                                         _spec_as_instance, _eat_self)
             _spec_signature = res and res[1]
@@ -624,7 +607,7 @@ class NonCallableMock(Base):
         dot = '.'
         if _name_list == ['()']:
             dot = ''
-        seen = set()
+
         while _parent is not None:
             last = _parent
 
@@ -635,11 +618,6 @@ class NonCallableMock(Base):
 
             _parent = _parent._mock_new_parent
 
-            # use ids here so as not to call __hash__ on the mocks
-            if id(_parent) in seen:
-                break
-            seen.add(id(_parent))
-
         _name_list = list(reversed(_name_list))
         _first = last._mock_name or 'mock'
         if len(_name_list) > 1:
@@ -753,8 +731,6 @@ class NonCallableMock(Base):
         message = 'expected call not found.\nExpected: %s\nActual: %s'
         expected_string = self._format_mock_call_signature(args, kwargs)
         call_args = self.call_args
-        if len(call_args) == 3:
-            call_args = call_args[1:]
         actual_string = self._format_mock_call_signature(*call_args)
         return message % (expected_string, actual_string)
 
@@ -992,8 +968,6 @@ class CallableMixin(Base):
         self.call_args = _call
         self.call_args_list.append(_call)
 
-        seen = set()
-
         # initial stuff for method_calls:
         do_method_calls = self._mock_parent is not None
         method_call_name = self._mock_name
@@ -1029,13 +1003,6 @@ class CallableMixin(Base):
             # follow the parental chain:
             _new_parent = _new_parent._mock_new_parent
 
-            # check we're not in an infinite loop:
-            # ( use ids here so as not to call __hash__ on the mocks)
-            _new_parent_id = id(_new_parent)
-            if _new_parent_id in seen:
-                break
-            seen.add(_new_parent_id)
-
         effect = self.side_effect
         if effect is not None:
             if _is_exception(effect):
@@ -1858,12 +1825,7 @@ def _set_return_value(mock, method, name):
 
     return_calulator = _calculate_return_value.get(name)
     if return_calulator is not None:
-        try:
-            return_value = return_calulator(mock)
-        except AttributeError:
-            # XXXX why do we return AttributeError here?
-            #      set it as a side_effect instead?
-            return_value = AttributeError(name)
+        return_value = return_calulator(mock)
         method.return_value = return_value
         return
 
@@ -1943,10 +1905,6 @@ class MagicProxy(object):
         self.name = name
         self.parent = parent
 
-    def __call__(self, *args, **kwargs):
-        m = self.create_mock()
-        return m(*args, **kwargs)
-
     def create_mock(self):
         entry = self.name
         parent = self.parent
@@ -2330,19 +2288,10 @@ def _must_skip(spec, entry, is_type):
         else:
             return False
 
-    # shouldn't get here unless function is a dynamically provided attribute
-    # XXXX untested behaviour
+    # function is a dynamically provided attribute
     return is_type
 
 
-def _get_class(obj):
-    try:
-        return obj.__class__
-    except AttributeError:
-        # it is possible for objects to have no __class__
-        return type(obj)
-
-
 class _SpecState(object):
 
     def __init__(self, spec, spec_set=False, parent=None,