How to execute code only on test failures with python unittest2?

Question

I have some class-based unit tests running in python\'s unittest2 framework. We\'re using Selenium WebDriver, which has a convenient save_screenshot() method. I

Answer 1

Use a decorator around each test.

The safest way to remember to decorate new tests, or to avoid going back and decorating a bunch of existing tests, is to use a metaclass to wrap all of the test functions. The How to wrap every method of a class? answer provides the basics of what you need.

You probably should filter the functions that are wrapped down to just the tests, e.g.:

class ScreenshotMetaClass(type):
    """Wraps all tests with screenshot_on_error"""
    def __new__(meta, classname, bases, classDict):
        newClassDict = {}
        for attributeName, attribute in classDict.items():
            if type(attribute) == FunctionType and 'test' in attributeName.lower():
                # replace the function with a wrapped version
                attribute = screenshot_on_error(attribute)
            newClassDict[attributeName] = attribute
        return type.__new__(meta, classname, bases, newClassDict)