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# Class for unittest support.  Used for capturing stderr/stdout.

import sys

from StringIO import StringIO

class OutputCapture(object):

    def __init__(self):

        self.saved_outputs = dict()

    def _capture_output_with_name(self, output_name):

        self.saved_outputs[output_name] = getattr(sys, output_name)

        setattr(sys, output_name, StringIO())

    def _restore_output_with_name(self, output_name):

        captured_output = getattr(sys, output_name).getvalue()

        setattr(sys, output_name, self.saved_outputs[output_name])

        del self.saved_outputs[output_name]

        return captured_output

    def capture_output(self):

        self._capture_output_with_name("stdout")

        self._capture_output_with_name("stderr")

    def restore_output(self):

        return (self._restore_output_with_name("stdout"), self._restore_output_with_name("stderr"))

    def assert_outputs(self, testcase, function, args=[], kwargs={}, expected_stdout="", expected_stderr="", expected_exception=None):

        self.capture_output()

        if expected_exception:

            return_value = testcase.assertRaises(expected_exception, function, *args, **kwargs)

        else:

            return_value = function(*args, **kwargs)

        (stdout_string, stderr_string) = self.restore_output()

        testcase.assertEqual(stdout_string, expected_stdout)

        testcase.assertEqual(stderr_string, expected_stderr)

        # This is a little strange, but I don't know where else to return this information.

        return return_value