exiv2/tests/system_tests.py

# -*- coding: utf-8 -*-

import configparser
import os
import inspect
import subprocess
import threading
import shlex
import sys
import shutil
import unittest


if sys.platform == 'win32':
    def _cmd_splitter(cmd):
        return cmd

    def _process_output_post(output):
        return output.replace('\r\n', '\n')

else:
    def _cmd_splitter(cmd):
        return shlex.split(cmd)

    def _process_output_post(output):
        return output


def _disjoint_dict_merge(d1, d2):
    """
    Merges two dictionaries with no common keys together and returns the result.

    >>> d1 = {"a": 1}
    >>> d2 = {"b": 2, "c": 3}
    >>> _disjoint_dict_merge(d1, d2) == {"a": 1, "b": 2, "c": 3}
    True

    Calling this function with dictionaries that share keys raises a ValueError:
    >>> _disjoint_dict_merge({"a": 1, "b": 6}, {"b": 2, "a": 3})
    Traceback (most recent call last):
     ..
    ValueError: Dictionaries have common keys.

    """
    inter = set(d1.keys()).intersection(set(d2.keys()))
    if len(inter) > 0:
        raise ValueError("Dictionaries have common keys.")
    res = d1.copy()
    res.update(d2)
    return res


_parameters = {}


def configure_suite(config_file):
    """
    Populates a global datastructure with the parameters from the suite's
    configuration file.

    This function performs the following steps:
    1. read in the file ``config_file`` via the ConfigParser module using
       extended interpolation
    2. check that the sections ``variables`` and ``paths`` are disjoint
    3. extract the environment variables given in the ``ENV`` section
    4. save all entries from the ``variables`` section in the global
       datastructure
    5. interpret all entries in the ``paths`` section as relative paths from the
       configuration file, expand them to absolute paths and save them in the
       global datastructure

    For further information concerning the rationale behind this, please consult
    the documentation in ``doc.md``.
    """

    if not os.path.exists(config_file):
        raise ValueError(
            "Test suite config file {:s} does not exist"
            .format(os.path.abspath(config_file))
        )

    config = configparser.ConfigParser(
        interpolation=configparser.ExtendedInterpolation(),
        delimiters=(':'),
        comment_prefixes=('#')
    )
    config.read(config_file)

    _parameters["suite_root"] = os.path.split(os.path.abspath(config_file))[0]
    _parameters["timeout"] = config.getfloat("General", "timeout", fallback=1.0)

    if 'variables' in config and 'paths' in config:
        intersecting_keys = set(config["paths"].keys())\
                            .intersection(set(config["variables"].keys()))
        if len(intersecting_keys) > 0:
            raise ValueError(
                "The sections 'paths' and 'variables' must not share keys, "
                "but they have the following common key{:s}: {:s}"
                .format(
                    's' if len(intersecting_keys) > 1 else '',
                    ', '.join(k for k in intersecting_keys)
                )
            )

    # extract variables from the environment
    for key in config['ENV']:
        if key in config['ENV fallback']:
            fallback = config['ENV fallback'][key]
        else:
            fallback = ""
        config['ENV'][key] = os.getenv(config['ENV'][key]) or fallback

    if 'variables' in config:
        for key in config['variables']:
            _parameters[key] = config['variables'][key]

    if 'paths' in config:
        for key in config['paths']:
            rel_path = config['paths'][key]
            abs_path = os.path.abspath(
                os.path.join(_parameters["suite_root"], rel_path)
            )
            if not os.path.exists(abs_path):
                raise ValueError(
                    "Path replacement for {short}: {abspath} does not exist"
                    " (was expanded from {rel})".format(
                        short=key,
                        abspath=abs_path,
                        rel=rel_path)
                )
            _parameters[key] = abs_path


def _setUp_factory(old_setUp, *files):
    """
    Factory function that returns a setUp function suitable to replace the
    existing setUp of a unittest.TestCase. The returned setUp calls at first
    old_setUp(self) and then creates a copy of all files in *files with the
    name: fname.ext -> fname_copy.ext

    All file names in *files are at first expanded using self.expand_variables()
    and the path to the copy is saved in self._file_copies
    """
    def setUp(self):
        old_setUp(self)
        self._file_copies = []
        for f in files:
            expanded_fname = self.expand_variables(f)
            fname, ext = os.path.splitext(expanded_fname)
            new_name = fname + '_copy' + ext
            self._file_copies.append(
                shutil.copyfile(expanded_fname, new_name)
            )
    return setUp


def _tearDown_factory(old_tearDown):
    """
    Factory function that returns a new tearDown method to replace an existing
    tearDown method. It at first deletes all files in self._file_copies and then
    calls old_tearDown(self).
    This factory is intended to be used in conjunction with _setUp_factory
    """
    def tearDown(self):
        for f in self._file_copies:
            os.remove(f)
        old_tearDown(self)
    return tearDown


def CopyFiles(*files):
    """
    Decorator for subclasses of system_test.Case that automatically creates a
    copy of the files specified as the parameters to the decorator.

    Example:
    >>> @CopyFiles("{some_var}/file.txt", "{another_var}/other_file.png")
        class Foo(Case):
            pass

    The decorator will inject new setUp method that at first calls the already
    defined setUp(), then expands all supplied file names using
    Case.expand_variables and then creates copies by appending '_copy' before
    the file extension. The paths to the copies are stored in self._file_copies.

    The decorator also injects a new tearDown method that deletes all files in
    self._file_copies and then calls the original tearDown method.

    This function will also complain if it is called without arguments or
    without paranthesis, which is valid decorator syntax but is obviously a bug
    in this case.
    """
    if len(files) == 0:
        raise ValueError("No files to copy supplied.")
    elif len(files) == 1:
        if isinstance(files[0], type):
            raise UserWarning(
                "Decorator used wrongly, must be called with filenames in paranthesis"
            )

    def wrapper(cls):
        old_setUp = cls.setUp
        cls.setUp = _setUp_factory(old_setUp, *files)

        old_tearDown = cls.tearDown
        cls.tearDown = _tearDown_factory(old_tearDown)

        return cls

    return wrapper


class Case(unittest.TestCase):
    """
    System test case base class, provides the functionality to interpret static
    class members as system tests and runs them.

    This class reads in the members commands, retval, stdout, stderr and runs
    the format function on each, where format is called with the kwargs being a
    merged dictionary of all variables that were extracted from the suite's
    configuration file and all static members of the current class.

    The resulting commands are then run using the subprocess module and compared
    against the expected values that were provided in the static
    members. Furthermore a threading.Timer is used to abort the execution if a
    configured timeout is reached.

    The class itself must be inherited from, otherwise it is not useful at all,
    as it does not provide any static members that could be used to run system
    tests. However, a class that inherits from this class needn't provide any
    member functions at all, the inherited test_run() function performs all
    required functionality in child classes.
    """

    """ maxDiff set so that arbitrarily large diffs will be shown """
    maxDiff = None

    @classmethod
    def setUpClass(cls):
        """
        This function adds the variables variable_dict & work_dir to the class.

        work_dir - set to the file where the current class is defined
        variable_dict - a merged dictionary of all static members of the current
                        class and all variables extracted from the suite's
                        configuration file
        """
        cls.variable_dict = _disjoint_dict_merge(cls.__dict__, _parameters)
        cls.work_dir = os.path.dirname(inspect.getfile(cls))

    def compare_stdout(self, i, command, got_stdout, expected_stdout):
        """
        Function to compare whether the expected & obtained stdout match.

        This function is automatically invoked by test_run with the following
        parameters:
        i - the index of the current command that is run in self.commands
        command - the command that was run
        got_stdout - the obtained stdout, post-processed depending on the
                     platform so that lines always end with \n
        expected_stdout - the expected stdout extracted from self.stdout

        The default implementation simply uses assertMultiLineEqual from
        unittest.TestCase. This function can be overridden in a child class to
        implement a custom check.
        """
        self.assertMultiLineEqual(expected_stdout, got_stdout)

    def compare_stderr(self, i, command, got_stderr, expected_stderr):
        """
        Same as compare_stdout only for standard-error.
        """
        self.assertMultiLineEqual(expected_stderr, got_stderr)

    def expand_variables(self, string):
        """
        Expands all variables in curly braces in the given string using the
        dictionary variable_dict.

        The expansion itself is performed by the builtin string method format().
        A KeyError indicates that the supplied string contains a variable
        in curly braces that is missing from self.variable_dict
        """
        return str(string).format(**self.variable_dict)

    def test_run(self):
        """
        Actual system test function which runs the provided commands,
        pre-processes all variables and post processes the output before passing
        it on to compare_stderr() & compare_stdout().
        """

        for i, command, retval, stdout, stderr in zip(range(len(self.commands)),
                                                      self.commands,
                                                      self.retval,
                                                      self.stdout,
                                                      self.stderr):
            command, retval, stdout, stderr = map(
                self.expand_variables, [command, retval, stdout, stderr]
            )
            retval = int(retval)
            timeout = {"flag": False}

            proc = subprocess.Popen(
                _cmd_splitter(command),
                stdout=subprocess.PIPE,
                stderr=subprocess.PIPE,
                cwd=self.work_dir
            )

            def timeout_reached(timeout):
                timeout["flag"] = True
                proc.kill()

            t = threading.Timer(
                _parameters["timeout"], timeout_reached, args=[timeout]
            )
            t.start()
            got_stdout, got_stderr = proc.communicate()
            t.cancel()

            self.assertFalse(timeout["flag"] and "Timeout reached")
            self.compare_stdout(
                i, command,
                _process_output_post(got_stdout.decode('utf-8')), stdout
            )
            self.compare_stderr(
                i, command,
                _process_output_post(got_stderr.decode('utf-8')), stderr
            )
            self.assertEqual(retval, proc.returncode)