Include __traceback_info__ in tracebacks printed by nose
Have you ever wanted supplemental (debugging) info included in an error or failure traceback produced by nose? Do you find that nose’s Failure Detail plugin fails you (for example, because you use PyHamcrest matchers)? Developing server software using Zope, Plone, Paste or WebError? Then this plugin might be the solution you’re looking for: it allows you to add whatever detailed information you want to any frame in your traceback. Turn a traceback like this:
Traceback (most recent call last): File "/.../nti.nose_traceback_info/src/nti/nose_traceback_info/tests/test_nose_traceback_info.py", line 39, in test_format_failure t, formatted, _ = self.plugin.formatFailure(None, exc_info) File "/.../nti.nose_traceback_info/src/nti/nose_traceback_info/__init__.py", line 48, in formatFailure return self.formatError( test, exc_info) File "/.../nti.nose_traceback_info/src/nti/nose_traceback_info/__init__.py", line 31, in formatError t, v, tb = exc_info TypeError: 'builtin_function_or_method' object is not iterable
into a traceback like this:
TypeError: Traceback (most recent call last): Module unittest.case, line 331, in run testMethod() Module nti.nose_traceback_info.tests.test_nose_traceback_info, line 39, in test_format_failure t, formatted, _ = self.plugin.formatFailure(None, exc_info) - __traceback_info__: ("calling plugin with test and exc_info", None, <build-in function exc_info>) Module nti.nose_traceback_info, line 48, in formatFailure return self.formatError( test, exc_info) Module nti.nose_traceback_info, line 31, in formatError t, v, tb = exc_info - __traceback_info__: ("Test and exc_info args", None, <built-in function exc_info>) TypeError: 'builtin_function_or_method' object is not iterable
Once the plugin is installed (using pip or in a setup.py or requirements.txt file), it is enabled by default, just like logcapture. The plugin operates by looking for local variables in each frame in a traceback and formatting them (both in captured logs and tracebacks displayed for failured tests). The variables are defined by conventions developed (and documented) by Zope; these conventions are also followed by Paste and WebError, meaning that information added to help debug tests can also be used to debug production errors.
See that documentation for details on the variables. As a quick start, the most important and most commonly used variable is __traceback_info__, to which you can assign arbitrary information. The repr of __traceback_info__ is included in the traceback:
def formatError(self, test, exc_info): __traceback_info__ = "Test and exc_info args", test, exc_info t, v, tb = exc_info
In addition to the standard environment variable and flags to enable the plugin, additional options control some behaviour.
- Use complete filenames, not module names, in formatted tracebacks.
- Do not format tracebacks captured in logs.
This plugin is known to cooperate correctly with nose-progressive, which also adjusts the traceback.
- By default, show filenames instead of module names. This cooperates better with IDE test integration.