Question

I want to check for an exception in Python unittest, with the following requirements:

• Needs to be reported as a failure, NOT an error
• Must not swallow the original exception

I’ve seen lots of solutions of the form:

try:
    something()
except:
    self.fail("It failed")

Unfortunately these solutions swallow the original exception. Any way to retain the original exception?

I ended up using a variant of Pierre GM’s answer:

try:
   something()
except:
    self.fail("Failed with %s" % traceback.format_exc())

Answer 1

As suggested, you could use the context of a generic exception:

except Exception, error:
    self.fail("Failed with %s" % error)

You can also retrieve the information relative to the exception through sys.exc_info()

try:
    1./0
except:
    (etype, evalue, etrace) = sys.exc_info()
    self.fail("Failed with %s" % evalue)

The tuple (etype, evalue, etrace) is here (<type 'exceptions.ZeroDivisionError'>, ZeroDivisionError('float division',), <traceback object at 0x7f6f2c02fa70>)