1# Copyright (c) 2009, Google Inc. All rights reserved.
2#
3# Redistribution and use in source and binary forms, with or without
4# modification, are permitted provided that the following conditions are
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7#     * Redistributions of source code must retain the above copyright
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9#     * Redistributions in binary form must reproduce the above
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11# in the documentation and/or other materials provided with the
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14# contributors may be used to endorse or promote products derived from
15# this software without specific prior written permission.
16#
17# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
18# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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20# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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22# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
23# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
24# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
25# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
27# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28#
29# Class for unittest support.  Used for capturing stderr/stdout.
30
31import sys
32from StringIO import StringIO
33
34class OutputCapture(object):
35    def __init__(self):
36        self.saved_outputs = dict()
37
38    def _capture_output_with_name(self, output_name):
39        self.saved_outputs[output_name] = getattr(sys, output_name)
40        setattr(sys, output_name, StringIO())
41
42    def _restore_output_with_name(self, output_name):
43        captured_output = getattr(sys, output_name).getvalue()
44        setattr(sys, output_name, self.saved_outputs[output_name])
45        del self.saved_outputs[output_name]
46        return captured_output
47
48    def capture_output(self):
49        self._capture_output_with_name("stdout")
50        self._capture_output_with_name("stderr")
51
52    def restore_output(self):
53        return (self._restore_output_with_name("stdout"), self._restore_output_with_name("stderr"))
54
55    def assert_outputs(self, testcase, function, args=[], kwargs={}, expected_stdout="", expected_stderr=""):
56        self.capture_output()
57        return_value = function(*args, **kwargs)
58        (stdout_string, stderr_string) = self.restore_output()
59        testcase.assertEqual(stdout_string, expected_stdout)
60        testcase.assertEqual(stderr_string, expected_stderr)
61        # This is a little strange, but I don't know where else to return this information.
62        return return_value
63