Adding metaclass for tests - DocModifier

1 files changed, 89 insertions, 0 deletions

diff --git a/tests/util/helper/docmodifier.py b/tests/util/helper/docmodifier.py
new file mode 100644
index 000000000..6df8c1145
--- /dev/null
+++ b/tests/util/helper/docmodifier.py
@@ -0,0 +1,89 @@
+
+'''Helper metaclass do 'decorate' docstrings from base test case classes'''
+
+import new
+
+
+def copy_func(func):
+    '''Helper function to copy a function object (except docstring)'''
+    return new.function(func.func_code, func.func_globals, func.func_name,
+                        func.func_defaults, func.func_closure)
+
+
+class DocModifier(type):
+    '''Metaclass for modifiying method documentation.
+
+    It allows the managed class to modify the method documentation, adding
+    prefixes and suffixes to a given set of methods.
+
+    For example, you have some unittest.TestCases that run on different set
+    of data. These methods could be written once in a base class and the
+    inheriting class just setup different setUp/tearDown methods with the
+    proper data. To differentiate the methods when using docstrings, you
+    can add a suffix or prefix to the docstring.
+
+    Variables in the implementing class:
+
+    doc_prefix - The prefix to the docstring
+    doc_suffix - The suffix to the docstring
+    doc_filter - The function to filter the methods. If not provided, this
+                 no docstrings are changed.'''
+
+    def __new__(mcs, name, bases, dct):
+
+        # FIXME currently we have to define doc_filter on each subclass
+        filter_function = dct.get('doc_filter')
+        if not filter_function:
+            filter_function = lambda x: False
+
+        for base in bases:
+            for attr in [x for x in base.__dict__ if filter_function(x)]:
+                original = getattr(base, attr)
+
+                if original.__doc__:
+                    copy = copy_func(original)
+                    copy.__doc__ = (dct.get('doc_prefix', '') +
+                                    original.__doc__ +
+                                    dct.get('doc_suffix', ''))
+                    dct[attr] = copy
+
+        return type.__new__(mcs, name, bases, dct)
+
+    def __init__(mcs, name, bases, dct):
+        super(DocModifier, mcs).__init__(name, bases, dct)
+
+
+if __name__ == '__main__':
+
+    # tests
+    class BaseTest(object):
+        __metaclass__ = DocModifier
+
+        def testBase(self):
+            '''base'''
+
+        def testWithoutDoc(self):
+            pass
+
+    class Implementing(BaseTest):
+
+        doc_filter = lambda x: x.startswith('test')
+        doc_prefix = 'prefix'
+        doc_suffix = 'suffix'
+
+    class OnlyPrefix(BaseTest):
+
+        doc_filter = lambda x: x.startswith('test')
+        doc_prefix = 'prefix'
+
+    class OnlySuffix(BaseTest):
+
+        doc_filter = lambda x: x.startswith('test')
+        doc_suffix = 'suffix'
+
+    assert(Implementing.testBase.__doc__ == 'prefixbasesuffix')
+    assert(Implementing.testWithoutDoc.__doc__ == None)
+    assert(OnlySuffix.testBase.__doc__ == 'basesuffix')
+    assert(OnlySuffix.testWithoutDoc.__doc__ == None)
+    assert(OnlyPrefix.testBase.__doc__ == 'prefixbase')
+    assert(OnlyPrefix.testWithoutDoc.__doc__ == None)