path: root/lib/spack/spack/test/conftest.py

# Copyright 2013-2019 Lawrence Livermore National Security, LLC and other
# Spack Project Developers. See the top-level COPYRIGHT file for details.
#
# SPDX-License-Identifier: (Apache-2.0 OR MIT)

import collections
import copy
import inspect
import os
import os.path
import shutil
import xml.etree.ElementTree

import ordereddict_backport
import py
import pytest
import ruamel.yaml as yaml

from llnl.util.filesystem import remove_linked_tree

import spack.architecture
import spack.compilers
import spack.config
import spack.caches
import spack.database
import spack.directory_layout
import spack.environment as ev
import spack.package_prefs
import spack.paths
import spack.platforms.test
import spack.repo
import spack.stage
import spack.util.executable
from spack.util.pattern import Bunch
from spack.dependency import Dependency
from spack.package import PackageBase
from spack.fetch_strategy import FetchStrategyComposite, URLFetchStrategy
from spack.fetch_strategy import FetchError
from spack.spec import Spec
from spack.version import Version


#
# Disable any activate Spack environment BEFORE all tests
#
@pytest.fixture(scope='session', autouse=True)
def clean_user_environment():
    env_var = ev.spack_env_var in os.environ
    active = ev._active_environment

    if env_var:
        spack_env_value = os.environ.pop(ev.spack_env_var)
    if active:
        ev.deactivate()

    yield

    if env_var:
        os.environ[ev.spack_env_var] = spack_env_value
    if active:
        ev.activate(active)


# Hooks to add command line options or set other custom behaviors.
# They must be placed here to be found by pytest. See:
#
# https://docs.pytest.org/en/latest/writing_plugins.html
#
def pytest_addoption(parser):
    group = parser.getgroup("Spack specific command line options")
    group.addoption(
        '--fast', action='store_true', default=False,
        help='runs only "fast" unit tests, instead of the whole suite')


def pytest_collection_modifyitems(config, items):
    if not config.getoption('--fast'):
        # --fast not given, run all the tests
        return

    slow_tests = ['db', 'network', 'maybeslow']
    skip_as_slow = pytest.mark.skip(
        reason='skipped slow test [--fast command line option given]'
    )
    for item in items:
        if any(x in item.keywords for x in slow_tests):
            item.add_marker(skip_as_slow)


#
# These fixtures are applied to all tests
#
@pytest.fixture(scope='function', autouse=True)
def no_chdir():
    """Ensure that no test changes Spack's working dirctory.

    This prevents Spack tests (and therefore Spack commands) from
    changing the working directory and causing other tests to fail
    mysteriously. Tests should use ``working_dir`` or ``py.path``'s
    ``.as_cwd()`` instead of ``os.chdir`` to avoid failing this check.

    We assert that the working directory hasn't changed, unless the
    original wd somehow ceased to exist.

    """
    original_wd = os.getcwd()
    yield
    if os.path.isdir(original_wd):
        assert os.getcwd() == original_wd


@pytest.fixture(scope='function', autouse=True)
def reset_compiler_cache():
    """Ensure that the compiler cache is not shared across Spack tests

    This cache can cause later tests to fail if left in a state incompatible
    with the new configuration. Since tests can make almost unlimited changes
    to their setup, default to not use the compiler cache across tests."""
    spack.compilers._compiler_cache = {}
    yield
    spack.compilers._compiler_cache = {}


@pytest.fixture
def clear_stage_root(monkeypatch):
    """Ensure spack.stage._stage_root is not set at test start."""
    monkeypatch.setattr(spack.stage, '_stage_root', None)
    yield


@pytest.fixture(scope='function', autouse=True)
def mock_stage(clear_stage_root, tmpdir_factory, request):
    """Establish the temporary build_stage for the mock archive."""
    # Workaround to skip mock_stage for 'nomockstage' test cases
    if 'nomockstage' not in request.keywords:
        new_stage = tmpdir_factory.mktemp('mock-stage')
        new_stage_path = str(new_stage)

        # Set test_stage_path as the default directory to use for test stages.
        current = spack.config.get('config:build_stage')
        spack.config.set('config',
                         {'build_stage': new_stage_path}, scope='user')

        # Ensure the source directory exists
        source_path = new_stage.join(spack.stage._source_path_subdir)
        source_path.ensure(dir=True)

        yield new_stage_path

        spack.config.set('config', {'build_stage': current}, scope='user')

        # Clean up the test stage directory
        if os.path.isdir(new_stage_path):
            shutil.rmtree(new_stage_path)
    else:
        # Must yield a path to avoid a TypeError on test teardown
        yield str(tmpdir_factory)


@pytest.fixture(scope='session')
def ignore_stage_files():
    """Session-scoped helper for check_for_leftover_stage_files.

    Used to track which leftover files in the stage have been seen.
    """
    # to start with, ignore the .lock file at the stage root.
    return set(['.lock', spack.stage._source_path_subdir])


def remove_whatever_it_is(path):
    """Type-agnostic remove."""
    if os.path.isfile(path):
        os.remove(path)
    elif os.path.islink(path):
        remove_linked_tree(path)
    else:
        shutil.rmtree(path)


@pytest.fixture
def working_env():
    saved_env = os.environ.copy()
    yield
    # os.environ = saved_env doesn't work
    # it causes module_parsing::test_module_function to fail
    # when it's run after any test using this fixutre
    os.environ.clear()
    os.environ.update(saved_env)


@pytest.fixture(scope='function', autouse=True)
def check_for_leftover_stage_files(request, mock_stage, ignore_stage_files):
    """Ensure that each test leaves a clean stage when done.

    This can be disabled for tests that are expected to dirty the stage
    by adding::

        @pytest.mark.disable_clean_stage_check

    to tests that need it.
    """
    stage_path = mock_stage

    yield

    files_in_stage = set()
    if os.path.exists(stage_path):
        stage_files = os.listdir(stage_path)
        files_in_stage = set(stage_files) - ignore_stage_files

    if 'disable_clean_stage_check' in request.keywords:
        # clean up after tests that are expected to be dirty
        for f in files_in_stage:
            path = os.path.join(stage_path, f)
            remove_whatever_it_is(path)
    else:
        ignore_stage_files |= files_in_stage
        assert not files_in_stage


@pytest.fixture(autouse=True)
def mock_fetch_cache(monkeypatch):
    """Substitutes spack.paths.fetch_cache with a mock object that does nothing
    and raises on fetch.
    """
    class MockCache(object):
        def store(self, copy_cmd, relative_dest):
            pass

        def fetcher(self, target_path, digest, **kwargs):
            return MockCacheFetcher()

    class MockCacheFetcher(object):
        def set_stage(self, stage):
            pass

        def fetch(self):
            raise FetchError('Mock cache always fails for tests')

        def __str__(self):
            return "[mock fetch cache]"

    monkeypatch.setattr(spack.caches, 'fetch_cache', MockCache())


@pytest.fixture(autouse=True)
def _skip_if_missing_executables(request):
    """Permits to mark tests with 'require_executables' and skip the
    tests if the executables passed as arguments are not found.
    """
    if request.node.get_marker('requires_executables'):
        required_execs = request.node.get_marker('requires_executables').args
        missing_execs = [
            x for x in required_execs if spack.util.executable.which(x) is None
        ]
        if missing_execs:
            msg = 'could not find executables: {0}'
            pytest.skip(msg.format(', '.join(missing_execs)))


# FIXME: The lines below should better be added to a fixture with
# FIXME: session-scope. Anyhow doing it is not easy, as it seems
# FIXME: there's some weird interaction with compilers during concretization.
spack.architecture.real_platform = spack.architecture.platform
spack.architecture.platform = lambda: spack.platforms.test.Test()

##########
# Test-specific fixtures
##########


@pytest.fixture(scope='session')
def repo_path():
    """Session scoped RepoPath object pointing to the mock repository"""
    return spack.repo.RepoPath(spack.paths.mock_packages_path)


@pytest.fixture(scope='module')
def mock_packages(repo_path):
    """Use the 'builtin.mock' repository instead of 'builtin'"""
    mock_repo = copy.deepcopy(repo_path)
    with spack.repo.swap(mock_repo):
        yield


@pytest.fixture(scope='function')
def mutable_mock_packages(mock_packages, repo_path):
    """Function-scoped mock packages, for tests that need to modify them."""
    mock_repo = copy.deepcopy(repo_path)
    with spack.repo.swap(mock_repo):
        yield


@pytest.fixture(scope='session')
def linux_os():
    """Returns a named tuple with attributes 'name' and 'version'
    representing the OS.
    """
    platform = spack.architecture.platform()
    name, version = 'debian', '6'
    if platform.name == 'linux':
        platform = spack.architecture.platform()
        current_os = platform.operating_system('default_os')
        name, version = current_os.name, current_os.version
    LinuxOS = collections.namedtuple('LinuxOS', ['name', 'version'])
    return LinuxOS(name=name, version=version)


@pytest.fixture(scope='session')
def configuration_dir(tmpdir_factory, linux_os):
    """Copies mock configuration files in a temporary directory. Returns the
    directory path.
    """
    tmpdir = tmpdir_factory.mktemp('configurations')

    # Name of the yaml files in the test/data folder
    test_path = py.path.local(spack.paths.test_path)
    compilers_yaml = test_path.join('data', 'compilers.yaml')
    packages_yaml = test_path.join('data', 'packages.yaml')
    config_yaml = test_path.join('data', 'config.yaml')
    repos_yaml = test_path.join('data', 'repos.yaml')

    # Create temporary 'site' and 'user' folders
    tmpdir.ensure('site', dir=True)
    tmpdir.ensure('user', dir=True)

    # Copy the configurations that don't need further work
    packages_yaml.copy(tmpdir.join('site', 'packages.yaml'))
    config_yaml.copy(tmpdir.join('site', 'config.yaml'))
    repos_yaml.copy(tmpdir.join('site', 'repos.yaml'))

    # Write the one that needs modifications
    content = ''.join(compilers_yaml.read()).format(linux_os)
    t = tmpdir.join('site', 'compilers.yaml')
    t.write(content)
    yield tmpdir

    # Once done, cleanup the directory
    shutil.rmtree(str(tmpdir))


@pytest.fixture(scope='module')
def config(configuration_dir):
    """Hooks the mock configuration files into spack.config"""
    # Set up a mock config scope
    spack.package_prefs.PackagePrefs.clear_caches()

    real_configuration = spack.config.config

    defaults = spack.config.InternalConfigScope(
        '_builtin', spack.config.config_defaults
    )
    test_scopes = [defaults]
    test_scopes += [
        spack.config.ConfigScope(name, str(configuration_dir.join(name)))
        for name in ['site', 'system', 'user']]
    test_scopes.append(spack.config.InternalConfigScope('command_line'))

    spack.config.config = spack.config.Configuration(*test_scopes)

    yield spack.config.config

    spack.config.config = real_configuration
    spack.package_prefs.PackagePrefs.clear_caches()


@pytest.fixture(scope='function')
def mutable_config(tmpdir_factory, configuration_dir, monkeypatch):
    """Like config, but tests can modify the configuration."""
    spack.package_prefs.PackagePrefs.clear_caches()

    mutable_dir = tmpdir_factory.mktemp('mutable_config').join('tmp')
    configuration_dir.copy(mutable_dir)

    cfg = spack.config.Configuration(
        *[spack.config.ConfigScope(name, str(mutable_dir))
          for name in ['site', 'system', 'user']])
    monkeypatch.setattr(spack.config, 'config', cfg)

    # This is essential, otherwise the cache will create weird side effects
    # that will compromise subsequent tests if compilers.yaml is modified
    monkeypatch.setattr(spack.compilers, '_cache_config_file', [])

    yield spack.config.config

    spack.package_prefs.PackagePrefs.clear_caches()


@pytest.fixture()
def mock_config(tmpdir):
    """Mocks two configuration scopes: 'low' and 'high'."""
    real_configuration = spack.config.config

    spack.config.config = spack.config.Configuration(
        *[spack.config.ConfigScope(name, str(tmpdir.join(name)))
          for name in ['low', 'high']])

    yield spack.config.config

    spack.config.config = real_configuration


def _populate(mock_db):
    r"""Populate a mock database with packages.

    Here is what the mock DB looks like:

    o  mpileaks     o  mpileaks'    o  mpileaks''
    |\              |\              |\
    | o  callpath   | o  callpath'  | o  callpath''
    |/|             |/|             |/|
    o |  mpich      o |  mpich2     o |  zmpi
      |               |             o |  fake
      |               |               |
      |               |______________/
      | .____________/
      |/
      o  dyninst
      |\
      | o  libdwarf
      |/
      o  libelf
    """
    def _install(spec):
        s = spack.spec.Spec(spec).concretized()
        pkg = spack.repo.get(s)
        pkg.do_install(fake=True, explicit=True)

    # Transaction used to avoid repeated writes.
    with mock_db.write_transaction():
        _install('mpileaks ^mpich')
        _install('mpileaks ^mpich2')
        _install('mpileaks ^zmpi')
        _install('externaltest')


@pytest.fixture(scope='session')
def _store_dir_and_cache(tmpdir_factory):
    """Returns the directory where to build the mock database and
    where to cache it.
    """
    store = tmpdir_factory.mktemp('mock_store')
    cache = tmpdir_factory.mktemp('mock_store_cache')
    return store, cache


@pytest.fixture(scope='module')
def database(tmpdir_factory, mock_packages, config, _store_dir_and_cache):
    """Creates a read-only mock database with some packages installed note
    that the ref count for dyninst here will be 3, as it's recycled
    across each install.
    """
    real_store = spack.store.store
    store_path, store_cache = _store_dir_and_cache

    mock_store = spack.store.Store(str(store_path))
    spack.store.store = mock_store

    # If the cache does not exist populate the store and create it
    if not os.path.exists(str(store_cache.join('.spack-db'))):
        _populate(mock_store.db)
        store_path.copy(store_cache, mode=True, stat=True)

    # Make the database read-only to ensure we can't modify entries
    store_path.join('.spack-db').chmod(mode=0o555, rec=1)

    yield mock_store.db

    store_path.join('.spack-db').chmod(mode=0o755, rec=1)
    spack.store.store = real_store


@pytest.fixture(scope='function')
def mutable_database(database, _store_dir_and_cache):
    """Writeable version of the fixture, restored to its initial state
    after each test.
    """
    # Make the database writeable, as we are going to modify it
    store_path, store_cache = _store_dir_and_cache
    store_path.join('.spack-db').chmod(mode=0o755, rec=1)

    yield database

    # Restore the initial state by copying the content of the cache back into
    # the store and making the database read-only
    store_path.remove(rec=1)
    store_cache.copy(store_path, mode=True, stat=True)
    store_path.join('.spack-db').chmod(mode=0o555, rec=1)


@pytest.fixture(scope='function')
def install_mockery(tmpdir, config, mock_packages):
    """Hooks a fake install directory, DB, and stage directory into Spack."""
    real_store = spack.store.store
    spack.store.store = spack.store.Store(str(tmpdir.join('opt')))

    # We use a fake package, so temporarily disable checksumming
    with spack.config.override('config:checksum', False):
        yield

    tmpdir.join('opt').remove()
    spack.store.store = real_store


@pytest.fixture()
def mock_fetch(mock_archive):
    """Fake the URL for a package so it downloads from a file."""
    fetcher = FetchStrategyComposite()
    fetcher.append(URLFetchStrategy(mock_archive.url))

    @property
    def fake_fn(self):
        return fetcher

    orig_fn = PackageBase.fetcher
    PackageBase.fetcher = fake_fn
    yield
    PackageBase.fetcher = orig_fn


class MockLayout(object):
    def __init__(self, root):
        self.root = root

    def path_for_spec(self, spec):
        return '/'.join([self.root, spec.name])

    def check_installed(self, spec):
        return True


@pytest.fixture()
def gen_mock_layout(tmpdir):
    # Generate a MockLayout in a temporary directory. In general the prefixes
    # specified by MockLayout should never be written to, but this ensures
    # that even if they are, that it causes no harm
    def create_layout(root):
        subroot = tmpdir.mkdir(root)
        return MockLayout(str(subroot))

    yield create_layout


@pytest.fixture()
def module_configuration(monkeypatch, request):
    """Reads the module configuration file from the mock ones prepared
    for tests and monkeypatches the right classes to hook it in.
    """
    # Class of the module file writer
    writer_cls = getattr(request.module, 'writer_cls')
    # Module where the module file writer is defined
    writer_mod = inspect.getmodule(writer_cls)
    # Key for specific settings relative to this module type
    writer_key = str(writer_mod.__name__).split('.')[-1]
    # Root folder for configuration
    root_for_conf = os.path.join(
        spack.paths.test_path, 'data', 'modules', writer_key
    )

    def _impl(filename):

        file = os.path.join(root_for_conf, filename + '.yaml')
        with open(file) as f:
            configuration = yaml.load(f)

        monkeypatch.setattr(
            spack.modules.common,
            'configuration',
            configuration
        )
        monkeypatch.setattr(
            writer_mod,
            'configuration',
            configuration[writer_key]
        )
        monkeypatch.setattr(
            writer_mod,
            'configuration_registry',
            {}
        )
    return _impl

##########
# Fake archives and repositories
##########


@pytest.fixture(scope='session')
def mock_archive(tmpdir_factory):
    """Creates a very simple archive directory with a configure script and a
    makefile that installs to a prefix. Tars it up into an archive.
    """
    tar = spack.util.executable.which('tar', required=True)

    tmpdir = tmpdir_factory.mktemp('mock-archive-dir')
    tmpdir.ensure(spack.stage._source_path_subdir, dir=True)
    repodir = tmpdir.join(spack.stage._source_path_subdir)

    # Create the configure script
    configure_path = str(tmpdir.join(spack.stage._source_path_subdir,
                                     'configure'))
    with open(configure_path, 'w') as f:
        f.write(
            "#!/bin/sh\n"
            "prefix=$(echo $1 | sed 's/--prefix=//')\n"
            "cat > Makefile <<EOF\n"
            "all:\n"
            "\techo Building...\n\n"
            "install:\n"
            "\tmkdir -p $prefix\n"
            "\ttouch $prefix/dummy_file\n"
            "EOF\n"
        )
    os.chmod(configure_path, 0o755)

    # Archive it
    with tmpdir.as_cwd():
        archive_name = '{0}.tar.gz'.format(spack.stage._source_path_subdir)
        tar('-czf', archive_name, spack.stage._source_path_subdir)

    Archive = collections.namedtuple('Archive',
                                     ['url', 'path', 'archive_file',
                                      'expanded_archive_basedir'])
    archive_file = str(tmpdir.join(archive_name))

    # Return the url
    yield Archive(
        url=('file://' + archive_file),
        archive_file=archive_file,
        path=str(repodir),
        expanded_archive_basedir=spack.stage._source_path_subdir)


@pytest.fixture(scope='session')
def mock_git_repository(tmpdir_factory):
    """Creates a very simple git repository with two branches and
    two commits.
    """
    git = spack.util.executable.which('git', required=True)

    tmpdir = tmpdir_factory.mktemp('mock-git-repo-dir')
    tmpdir.ensure(spack.stage._source_path_subdir, dir=True)
    repodir = tmpdir.join(spack.stage._source_path_subdir)

    # Initialize the repository
    with repodir.as_cwd():
        git('init')
        git('config', 'user.name', 'Spack')
        git('config', 'user.email', 'spack@spack.io')
        url = 'file://' + str(repodir)

        # r0 is just the first commit
        r0_file = 'r0_file'
        repodir.ensure(r0_file)
        git('add', r0_file)
        git('commit', '-m', 'mock-git-repo r0')

        branch = 'test-branch'
        branch_file = 'branch_file'
        git('branch', branch)

        tag_branch = 'tag-branch'
        tag_file = 'tag_file'
        git('branch', tag_branch)

        # Check out first branch
        git('checkout', branch)
        repodir.ensure(branch_file)
        git('add', branch_file)
        git('commit', '-m' 'r1 test branch')

        # Check out a second branch and tag it
        git('checkout', tag_branch)
        repodir.ensure(tag_file)
        git('add', tag_file)
        git('commit', '-m' 'tag test branch')

        tag = 'test-tag'
        git('tag', tag)

        git('checkout', 'master')

        # R1 test is the same as test for branch
        rev_hash = lambda x: git('rev-parse', x, output=str).strip()
        r1 = rev_hash(branch)
        r1_file = branch_file

    checks = {
        'master': Bunch(
            revision='master', file=r0_file, args={'git': url}
        ),
        'branch': Bunch(
            revision=branch, file=branch_file, args={
                'git': url, 'branch': branch
            }
        ),
        'tag-branch': Bunch(
            revision=tag_branch, file=tag_file, args={
                'git': url, 'branch': tag_branch
            }
        ),
        'tag': Bunch(
            revision=tag, file=tag_file, args={'git': url, 'tag': tag}
        ),
        'commit': Bunch(
            revision=r1, file=r1_file, args={'git': url, 'commit': r1}
        )
    }

    t = Bunch(checks=checks, url=url, hash=rev_hash,
              path=str(repodir), git_exe=git)
    yield t


@pytest.fixture(scope='session')
def mock_hg_repository(tmpdir_factory):
    """Creates a very simple hg repository with two commits."""
    hg = spack.util.executable.which('hg', required=True)

    tmpdir = tmpdir_factory.mktemp('mock-hg-repo-dir')
    tmpdir.ensure(spack.stage._source_path_subdir, dir=True)
    repodir = tmpdir.join(spack.stage._source_path_subdir)

    get_rev = lambda: hg('id', '-i', output=str).strip()

    # Initialize the repository
    with repodir.as_cwd():
        url = 'file://' + str(repodir)
        hg('init')

        # Commit file r0
        r0_file = 'r0_file'
        repodir.ensure(r0_file)
        hg('add', r0_file)
        hg('commit', '-m', 'revision 0', '-u', 'test')
        r0 = get_rev()

        # Commit file r1
        r1_file = 'r1_file'
        repodir.ensure(r1_file)
        hg('add', r1_file)
        hg('commit', '-m' 'revision 1', '-u', 'test')
        r1 = get_rev()

    checks = {
        'default': Bunch(
            revision=r1, file=r1_file, args={'hg': str(repodir)}
        ),
        'rev0': Bunch(
            revision=r0, file=r0_file, args={
                'hg': str(repodir), 'revision': r0
            }
        )
    }
    t = Bunch(checks=checks, url=url, hash=get_rev, path=str(repodir))
    yield t


@pytest.fixture(scope='session')
def mock_svn_repository(tmpdir_factory):
    """Creates a very simple svn repository with two commits."""
    svn = spack.util.executable.which('svn', required=True)
    svnadmin = spack.util.executable.which('svnadmin', required=True)

    tmpdir = tmpdir_factory.mktemp('mock-svn-stage')
    tmpdir.ensure(spack.stage._source_path_subdir, dir=True)
    repodir = tmpdir.join(spack.stage._source_path_subdir)
    url = 'file://' + str(repodir)

    # Initialize the repository
    with repodir.as_cwd():
        # NOTE: Adding --pre-1.5-compatible works for NERSC
        # Unknown if this is also an issue at other sites.
        svnadmin('create', '--pre-1.5-compatible', str(repodir))

        # Import a structure (first commit)
        r0_file = 'r0_file'
        tmpdir.ensure('tmp-path', r0_file)
        tmp_path = tmpdir.join('tmp-path')
        svn('import',
            str(tmp_path),
            url,
            '-m',
            'Initial import r0')
        tmp_path.remove()

        # Second commit
        r1_file = 'r1_file'
        svn('checkout', url, str(tmp_path))
        tmpdir.ensure('tmp-path', r1_file)

        with tmp_path.as_cwd():
            svn('add', str(tmpdir.ensure('tmp-path', r1_file)))
            svn('ci', '-m', 'second revision r1')

        tmp_path.remove()
        r0 = '1'
        r1 = '2'

    checks = {
        'default': Bunch(
            revision=r1, file=r1_file, args={'svn': url}),
        'rev0': Bunch(
            revision=r0, file=r0_file, args={
                'svn': url, 'revision': r0})
    }

    def get_rev():
        output = svn('info', '--xml', output=str)
        info = xml.etree.ElementTree.fromstring(output)
        return info.find('entry/commit').get('revision')

    t = Bunch(checks=checks, url=url, hash=get_rev, path=str(repodir))
    yield t


@pytest.fixture()
def mutable_mock_env_path(tmpdir_factory):
    """Fixture for mocking the internal spack environments directory."""
    saved_path = spack.environment.env_path
    mock_path = tmpdir_factory.mktemp('mock-env-path')
    spack.environment.env_path = str(mock_path)
    yield mock_path
    spack.environment.env_path = saved_path


@pytest.fixture()
def installation_dir_with_headers(tmpdir_factory):
    """Mock installation tree with a few headers placed in different
    subdirectories. Shouldn't be modified by tests as it is session
    scoped.
    """
    root = tmpdir_factory.mktemp('prefix')

    # Create a few header files:
    #
    # <prefix>
    # |-- include
    # |   |--boost
    # |   |   |-- ex3.h
    # |   |-- ex3.h
    # |-- path
    #     |-- to
    #         |-- ex1.h
    #         |-- subdir
    #             |-- ex2.h
    #
    root.ensure('include', 'boost', 'ex3.h')
    root.ensure('include', 'ex3.h')
    root.ensure('path', 'to', 'ex1.h')
    root.ensure('path', 'to', 'subdir', 'ex2.h')

    return root


##########
# Mock packages
##########


class MockPackage(object):
    def __init__(self, name, dependencies, dependency_types, conditions=None,
                 versions=None):
        self.name = name
        self.spec = None
        self.dependencies = ordereddict_backport.OrderedDict()
        self._installed_upstream = False

        assert len(dependencies) == len(dependency_types)
        for dep, dtype in zip(dependencies, dependency_types):
            d = Dependency(self, Spec(dep.name), type=dtype)
            if not conditions or dep.name not in conditions:
                self.dependencies[dep.name] = {Spec(name): d}
            else:
                dep_conditions = conditions[dep.name]
                dep_conditions = dict(
                    (Spec(x), Dependency(self, Spec(y), type=dtype))
                    for x, y in dep_conditions.items())
                self.dependencies[dep.name] = dep_conditions

        if versions:
            self.versions = versions
        else:
            versions = list(Version(x) for x in [1, 2, 3])
            self.versions = dict((x, {'preferred': False}) for x in versions)

        self.variants = {}
        self.provided = {}
        self.conflicts = {}
        self.patches = {}


class MockPackageMultiRepo(object):
    def __init__(self, packages):
        self.spec_to_pkg = dict((x.name, x) for x in packages)
        self.spec_to_pkg.update(
            dict(('mockrepo.' + x.name, x) for x in packages))

    def get(self, spec):
        if not isinstance(spec, spack.spec.Spec):
            spec = Spec(spec)
        return self.spec_to_pkg[spec.name]

    def get_pkg_class(self, name):
        return self.spec_to_pkg[name]

    def exists(self, name):
        return name in self.spec_to_pkg

    def is_virtual(self, name):
        return False

    def repo_for_pkg(self, name):
        import collections
        Repo = collections.namedtuple('Repo', ['namespace'])
        return Repo('mockrepo')

##########
# Specs of various kind
##########


@pytest.fixture(
    params=[
        'conflict%clang',
        'conflict%clang+foo',
        'conflict-parent%clang',
        'conflict-parent@0.9^conflict~foo'
    ]
)
def conflict_spec(request):
    """Specs which violate constraints specified with the "conflicts"
    directive in the "conflict" package.
    """
    return request.param


@pytest.fixture(
    params=[
        'conflict%~'
    ]
)
def invalid_spec(request):
    """Specs that do not parse cleanly due to invalid formatting.
    """
    return request.param


@pytest.fixture("module")
def mock_test_repo(tmpdir_factory):
    """Create an empty repository."""
    repo_namespace = 'mock_test_repo'
    repodir = tmpdir_factory.mktemp(repo_namespace)
    repodir.ensure(spack.repo.packages_dir_name, dir=True)
    yaml = repodir.join('repo.yaml')
    yaml.write("""
repo:
    namespace: mock_test_repo
""")

    repo = spack.repo.RepoPath(str(repodir))
    with spack.repo.swap(repo):
        yield repo, repodir

    shutil.rmtree(str(repodir))


##########
# Class and fixture to work around problems raising exceptions in directives,
# which cause tests like test_from_list_url to hang for Python 2.x metaclass
# processing.
#
# At this point only version and patch directive handling has been addressed.
##########

class MockBundle(object):
    has_code = False
    name = 'mock-bundle'
    versions = {}


@pytest.fixture
def mock_directive_bundle():
    """Return a mock bundle package for directive tests."""
    return MockBundle()


@pytest.fixture
def clear_directive_functions():
    """Clear all overidden directive functions for subsequent tests."""
    yield

    # Make sure any directive functions overidden by tests are cleared before
    # proceeding with subsequent tests that may depend on the original
    # functions.
    spack.directives.DirectiveMeta._directives_to_be_executed = []