def test_migrate_with_dry_run_flag(self, mock_file_config,
mocked_apply_migration, getLogger):
"""
Test that when a dry run is performed, no migrations actually occur.
"""
logger = MagicMock()
getLogger.return_value = logger
# Make sure we start out with a clean slate
self.assertEquals(MigrationTracker.get_collection().find({}).count(),
0)
# Make sure that our mock works. There are three valid packages.
self.assertEquals(len(models.get_migration_packages()), 4)
# Set all versions back to 0
for package in models.get_migration_packages():
package._migration_tracker.version = 0
package._migration_tracker.save()
result = manage.main()
# Test that none of the mock objects were actually called
migration_modules_called = [
mock_call[1][1].name
for mock_call in mocked_apply_migration.mock_calls
]
self.assertEquals(0, len(migration_modules_called))
self.assertEquals(1, result)
for package in models.get_migration_packages():
self.assertEqual(package.current_version, 0)
def test__initialize_pulp(self):
"""
_initialize_pulp() should raise an Exception if any of the packages aren't at their latest
version.
"""
# It is unusual to put an import in the middle of a test, but unfortunately this import will
# call start_logging() before our test super class can override the logging settings, and
# thus all the logging will be done to /var/log instead of to /tmp. Moving the import here
# from the top of the file solves the problem, though not elegantly.
from pulp.server.webservices.application import _initialize_pulp
# Make sure we start out with a clean slate
self.assertEquals(MigrationTracker.get_collection().find({}).count(), 0)
# Make sure that our mock works. There are three valid packages.
self.assertEquals(len(models.get_migration_packages()), 4)
# Set all versions back to 0
for package in models.get_migration_packages():
package._migration_tracker.version = 0
package._migration_tracker.save()
# Let's make sure we raise the exception
try:
_initialize_pulp()
self.fail('_initialize_pulp() should have raised an Exception, but did not.')
except Exception, e:
self.assertEqual(str(e), ('There are unapplied migrations. Please '
'run the database management utility to apply them.'))
def test_current_version_too_high(self, mocked_file_config, getLogger):
"""
Set the current package version higher than latest available version, then sit back and eat
popcorn.
"""
logger = MagicMock()
getLogger.return_value = logger
# Make sure we start out with a clean slate
self.assertEquals(MigrationTracker.get_collection().find({}).count(), 0)
# Make sure that our mock works. There are four valid packages.
self.assertEquals(len(models.get_migration_packages()), 4)
# Set all versions to ridiculously high values
for package in models.get_migration_packages():
package._migration_tracker.version = 9999999
package._migration_tracker.save()
error_code = manage.main()
self.assertEqual(error_code, os.EX_DATAERR)
# There should have been a critical log about the Exception
expected_messages = ('The database for migration package unit.server.db.migration_packages.'
'platform is at version 9999999, which is larger than the latest '
'version available, 1.')
critical_messages = ''.join([mock_call[1][0] for mock_call in logger.critical.mock_calls])
for msg in expected_messages:
self.assertTrue(msg in critical_messages)
def test_current_version_too_high(self, mocked_file_config, mocked_logger,
mocked_stdout, mocked_stderr):
"""
Set the current package version higher than latest available version, then sit back and eat
popcorn.
"""
# Make sure we start out with a clean slate
self.assertEquals(MigrationTracker.get_collection().find({}).count(),
0)
# Make sure that our mock works. There are four valid packages.
self.assertEquals(len(models.get_migration_packages()), 4)
# Set all versions to ridiculously high values
for package in models.get_migration_packages():
package._migration_tracker.version = 9999999
package._migration_tracker.save()
error_code = manage.main()
self.assertEqual(error_code, os.EX_DATAERR)
# There should have been a print to stderr about the Exception
expected_stderr_calls = [(
'The database for migration package unit.server.db.migration_packages.platform is at '
'version 9999999, which is larger than the latest version available, 1.'
), '\n']
stderr_calls = [
mock_call[1][0] for mock_call in mocked_stderr.mock_calls
]
self.assertEquals(stderr_calls, expected_stderr_calls)
def test_current_version_too_high(self, mocked_file_config, getLogger):
"""
Set the current package version higher than latest available version, then sit back and eat
popcorn.
"""
logger = MagicMock()
getLogger.return_value = logger
# Make sure we start out with a clean slate
self.assertEquals(MigrationTracker.get_collection().find({}).count(), 0)
# Make sure that our mock works. There are four valid packages.
self.assertEquals(len(models.get_migration_packages()), 4)
# Set all versions to ridiculously high values
for package in models.get_migration_packages():
package._migration_tracker.version = 9999999
package._migration_tracker.save()
error_code = manage.main()
self.assertEqual(error_code, os.EX_DATAERR)
# There should have been a critical log about the Exception
expected_messages = ('The database for migration package unit.server.db.migration_packages.'
'platform is at version 9999999, which is larger than the latest '
'version available, 1.')
critical_messages = ''.join([mock_call[1][0] for mock_call in logger.critical.mock_calls])
for msg in expected_messages:
self.assertTrue(msg in critical_messages)
def test_migrate(self, mock_file_config, mocked_apply_migration,
getLogger):
"""
Let's set all the packages to be at version 0, and then check that the migrations get
called in the correct order.
"""
logger = MagicMock()
getLogger.return_value = logger
# Make sure we start out with a clean slate
self.assertEquals(MigrationTracker.get_collection().find({}).count(),
0)
# Make sure that our mock works. There are three valid packages.
self.assertEquals(len(models.get_migration_packages()), 4)
# Set all versions back to 0
for package in models.get_migration_packages():
package._migration_tracker.version = 0
package._migration_tracker.save()
manage.main()
# There should have been a critical log about the Exception
expected_messages = (
'Applying migration unit.server.db.migration_packages.raise_exception.0002_oh_no '
'failed.\n\nHalting migrations due to a migration failure.',
"Bet you didn\'t see this coming.")
critical_messages = ''.join(
[mock_call[1][0] for mock_call in logger.critical.mock_calls])
for msg in expected_messages:
self.assertTrue(msg in critical_messages)
migration_modules_called = [
mock_call[1][1].name
for mock_call in mocked_apply_migration.mock_calls
]
# Note that none of the migrations that don't meet our criteria show up in this list. Also,
# Note that migration_packages.raise_exception.0003_shouldnt_run doesn't appear
# since migration_packages.raise_exception.0002_oh_no raised an Exception. Note
# also that even though the raise_exception package raised an Exception, we still run all
# the z migrations because we don't want one package to break another.
expected_migration_modules_called = [
'unit.server.db.migration_packages.platform.0001_stuff_and_junk',
'unit.server.db.migration_packages.raise_exception.0001_works_fine',
'unit.server.db.migration_packages.raise_exception.0002_oh_no'
]
self.assertEquals(migration_modules_called,
expected_migration_modules_called)
# Assert that our precious versions have been updated correctly
for package in models.get_migration_packages():
if package.name == 'unit.server.db.migration_packages.platform':
self.assertEqual(package.current_version,
package.latest_available_version)
elif package.name == 'unit.server.db.migration_packages.raise_exception':
# The raised Exception should have prevented us from getting past version 1
self.assertEquals(package.current_version, 1)
else:
# raise_exception should cause the migrations to stop
self.assertEqual(package.current_version, 0)
def test_migrate(self, file_config_mock, logger_mock,
mocked_apply_migration, mocked_stdout, mocked_stderr):
"""
Let's set all the packages to be at version 0, and then check that the migrations get
called in the correct order.
"""
# Make sure we start out with a clean slate
self.assertEquals(MigrationTracker.get_collection().find({}).count(),
0)
# Make sure that our mock works. There are three valid packages.
self.assertEquals(len(models.get_migration_packages()), 4)
# Set all versions back to 0
for package in models.get_migration_packages():
package._migration_tracker.version = 0
package._migration_tracker.save()
manage.main()
# There should have been a print to stderr about the Exception
expected_stderr_calls = [(
'Applying migration unit.server.db.migration_packages.raise_exception.0002_oh_no '
'failed.'), ' ', ' See log for details.', '\n']
stderr_calls = [
mock_call[1][0] for mock_call in mocked_stderr.mock_calls
]
self.assertEquals(stderr_calls, expected_stderr_calls)
migration_modules_called = [
mock_call[1][1].name
for mock_call in mocked_apply_migration.mock_calls
]
# Note that none of the migrations that don't meet our criteria show up in this list. Also,
# Note that migration_packages.raise_exception.0003_shouldnt_run doesn't appear
# since migration_packages.raise_exception.0002_oh_no raised an Exception. Note
# also that even though the raise_exception package raised an Exception, we still run all
# the z migrations because we don't want one package to break another.
expected_migration_modules_called = [
'unit.server.db.migration_packages.platform.0001_stuff_and_junk',
'unit.server.db.migration_packages.raise_exception.0001_works_fine',
'unit.server.db.migration_packages.raise_exception.0002_oh_no',
'unit.server.db.migration_packages.z.0001_test',
'unit.server.db.migration_packages.z.0002_test',
'unit.server.db.migration_packages.z.0003_test'
]
self.assertEquals(migration_modules_called,
expected_migration_modules_called)
# Assert that our precious versions have been updated correctly
for package in models.get_migration_packages():
if package.name != 'unit.server.db.migration_packages.raise_exception':
self.assertEqual(package.current_version,
package.latest_available_version)
else:
# The raised Exception should have prevented us from getting past version 1
self.assertEqual(package.current_version, 1)
def test_migrate(self, mock_file_config, mocked_apply_migration, getLogger):
"""
Let's set all the packages to be at version 0, and then check that the migrations get
called in the correct order.
"""
logger = MagicMock()
getLogger.return_value = logger
# Make sure we start out with a clean slate
self.assertEquals(MigrationTracker.get_collection().find({}).count(), 0)
# Make sure that our mock works. There are three valid packages.
self.assertEquals(len(models.get_migration_packages()), 4)
# Set all versions back to 0
for package in models.get_migration_packages():
package._migration_tracker.version = 0
package._migration_tracker.save()
manage.main()
# There should have been a critical log about the Exception
expected_messages = (
'Applying migration unit.server.db.migration_packages.raise_exception.0002_oh_no '
'failed.\n\nHalting migrations due to a migration failure.',
"Bet you didn\'t see this coming."
)
critical_messages = ''.join([mock_call[1][0] for mock_call in logger.critical.mock_calls])
for msg in expected_messages:
self.assertTrue(msg in critical_messages)
migration_modules_called = [
mock_call[1][1].name for mock_call in mocked_apply_migration.mock_calls]
# Note that none of the migrations that don't meet our criteria show up in this list. Also,
# Note that migration_packages.raise_exception.0003_shouldnt_run doesn't appear
# since migration_packages.raise_exception.0002_oh_no raised an Exception. Note
# also that even though the raise_exception package raised an Exception, we still run all
# the z migrations because we don't want one package to break another.
expected_migration_modules_called = [
'unit.server.db.migration_packages.platform.0001_stuff_and_junk',
'unit.server.db.migration_packages.raise_exception.0001_works_fine',
'unit.server.db.migration_packages.raise_exception.0002_oh_no']
self.assertEquals(migration_modules_called, expected_migration_modules_called)
# Assert that our precious versions have been updated correctly
for package in models.get_migration_packages():
if package.name == 'unit.server.db.migration_packages.platform':
self.assertEqual(package.current_version, package.latest_available_version)
elif package.name == 'unit.server.db.migration_packages.raise_exception':
# The raised Exception should have prevented us from getting past version 1
self.assertEquals(package.current_version, 1)
else:
# raise_exception should cause the migrations to stop
self.assertEqual(package.current_version, 0)
def test_migrate_with_test_flag(self, start_logging_mock,
mocked_apply_migration, mocked_stderr):
"""
Let's set all the packages to be at version 0, and then check that the migrations get called
in the correct order. We will also set the --test flag and ensure that the migration
versions do not get updated.
"""
# Make sure we start out with a clean slate
self.assertEquals(MigrationTracker.get_collection().find({}).count(),
0)
# Make sure that our mock works. There are three valid packages.
self.assertEquals(len(models.get_migration_packages()), 4)
# Set all versions back to 0
for package in models.get_migration_packages():
package._migration_tracker.version = 0
package._migration_tracker.save()
manage.main()
# There should have been a print to stderr about the Exception
expected_stderr_calls = [
'Applying migration data.test_migration_packages.raise_exception.0002_oh_no failed.',
' ', ' See log for details.', '\n'
]
stderr_calls = [call[1][0] for call in mocked_stderr.mock_calls]
self.assertEquals(stderr_calls, expected_stderr_calls)
migration_modules_called = [
call[1][1].name for call in mocked_apply_migration.mock_calls
]
# Note that none of the migrations that don't meet our criteria show up in this list. Also,
# Note that data.test_migration_packages.raise_exception.0003_shouldnt_run doesn't appear
# since data.test_migration_packages.raise_exception.0002_oh_no raised an Exception. Note
# also that even though the raise_exception package raised an Exception, we still run all
# the z migrations because we don't want one package to break another.
expected_migration_modules_called = [
'data.test_migration_packages.platform.0001_stuff_and_junk',
'data.test_migration_packages.raise_exception.0001_works_fine',
'data.test_migration_packages.raise_exception.0002_oh_no',
'data.test_migration_packages.z.0001_test',
'data.test_migration_packages.z.0002_test',
'data.test_migration_packages.z.0003_test'
]
self.assertEquals(migration_modules_called,
expected_migration_modules_called)
# Assert that our precious versions have not been updated, since we have the --test flag
for package in models.get_migration_packages():
self.assertEqual(package.current_version, 0)
def test_migrate(self, file_config_mock, logger_mock, mocked_apply_migration, mocked_stdout,
mocked_stderr):
"""
Let's set all the packages to be at version 0, and then check that the migrations get
called in the correct order.
"""
# Make sure we start out with a clean slate
self.assertEquals(MigrationTracker.get_collection().find({}).count(), 0)
# Make sure that our mock works. There are three valid packages.
self.assertEquals(len(models.get_migration_packages()), 4)
# Set all versions back to 0
for package in models.get_migration_packages():
package._migration_tracker.version = 0
package._migration_tracker.save()
manage.main()
# There should have been a print to stderr about the Exception
expected_stderr_calls = [
('Applying migration unit.server.db.migration_packages.raise_exception.0002_oh_no '
'failed.'), ' ', ' See log for details.', '\n']
stderr_calls = [mock_call[1][0] for mock_call in mocked_stderr.mock_calls]
self.assertEquals(stderr_calls, expected_stderr_calls)
migration_modules_called = [
mock_call[1][1].name for mock_call in mocked_apply_migration.mock_calls]
# Note that none of the migrations that don't meet our criteria show up in this list. Also,
# Note that migration_packages.raise_exception.0003_shouldnt_run doesn't appear
# since migration_packages.raise_exception.0002_oh_no raised an Exception. Note
# also that even though the raise_exception package raised an Exception, we still run all
# the z migrations because we don't want one package to break another.
expected_migration_modules_called = [
'unit.server.db.migration_packages.platform.0001_stuff_and_junk',
'unit.server.db.migration_packages.raise_exception.0001_works_fine',
'unit.server.db.migration_packages.raise_exception.0002_oh_no',
'unit.server.db.migration_packages.z.0001_test',
'unit.server.db.migration_packages.z.0002_test',
'unit.server.db.migration_packages.z.0003_test']
self.assertEquals(migration_modules_called, expected_migration_modules_called)
# Assert that our precious versions have been updated correctly
for package in models.get_migration_packages():
if package.name != 'unit.server.db.migration_packages.raise_exception':
self.assertEqual(package.current_version, package.latest_available_version)
else:
# The raised Exception should have prevented us from getting past version 1
self.assertEqual(package.current_version, 1)
def test_migrate_with_new_packages(self, start_logging_mock, logger_mock, mocked_stderr):
"""
Adding new packages to a system that doesn't have any trackers should advance
each package to the latest available version, applying all migrate() functions along the way.
"""
# Make sure we start out with a clean slate
self.assertEquals(MigrationTracker.get_collection().find({}).count(), 0)
# Make sure that our mock works. There are four valid packages.
self.assertEquals(len(models.get_migration_packages()), 4)
manage.main()
for package in models.get_migration_packages():
if 'raise_exception' in str(package):
# The Exception raising package should get to version 1, because version 2 raises
self.assertEqual(package.current_version, 1)
else:
# All other packages should reach their top versions
self.assertEqual(package.current_version, package.latest_available_version)
def test_current_version_too_high(self, mocked_file_config, mocked_logger, mocked_stderr):
"""
Set the current package version higher than latest available version, then sit back and eat
popcorn.
"""
# Make sure we start out with a clean slate
self.assertEquals(MigrationTracker.get_collection().find({}).count(), 0)
# Make sure that our mock works. There are four valid packages.
self.assertEquals(len(models.get_migration_packages()), 4)
# Set all versions to ridiculously high values
for package in models.get_migration_packages():
package._migration_tracker.version = 9999999
package._migration_tracker.save()
error_code = manage.main()
self.assertEqual(error_code, os.EX_DATAERR)
# There should have been a print to stderr about the Exception
expected_stderr_calls = [
'The database for migration package data.test_migration_packages.platform is at ' +\
'version 9999999, which is larger than the latest version available, 1.', '\n']
stderr_calls = [call[1][0] for call in mocked_stderr.mock_calls]
self.assertEquals(stderr_calls, expected_stderr_calls)
def test_migrate_with_new_packages(self, start_logging_mock, logger_mock,
mocked_stderr):
"""
Adding new packages to a system that doesn't have any trackers should advance
each package to the latest available version, applying all migrate() functions along the way.
"""
# Make sure we start out with a clean slate
self.assertEquals(MigrationTracker.get_collection().find({}).count(),
0)
# Make sure that our mock works. There are four valid packages.
self.assertEquals(len(models.get_migration_packages()), 4)
manage.main()
for package in models.get_migration_packages():
if 'raise_exception' in str(package):
# The Exception raising package should get to version 1, because version 2 raises
self.assertEqual(package.current_version, 1)
else:
# All other packages should reach their top versions
self.assertEqual(package.current_version,
package.latest_available_version)
def test_save(self):
# Make sure we are starting off clean
self.assertEquals(MigrationTracker.get_collection().find({}).count(), 0)
# Instantiate a MigrationTracker
mt = MigrationTracker('meaning_of_life', 41)
# At this point there should not be a MigrationTracker in the database
self.assertEquals(mt._collection.find({}).count(), 0)
# saving the mt should add it to the DB
mt.save()
self.assertEquals(mt._collection.find({}).count(), 1)
mt_bson = mt._collection.find_one({'name': 'meaning_of_life'})
self.assertEquals(mt_bson['name'], 'meaning_of_life')
self.assertEquals(mt_bson['version'], 41)
# now let's update the version to 42, the correct meaning of life
mt.version = 42
mt.save()
# see if the updated meaning of life made it to the DB
self.assertEquals(mt._collection.find({}).count(), 1)
mt_bson = mt._collection.find_one({'name': 'meaning_of_life'})
self.assertEquals(mt_bson['name'], 'meaning_of_life')
self.assertEquals(mt_bson['version'], 42)
def test_migrate_with_new_packages(self, mocked_apply_migration):
"""
Adding new packages to a system that doesn't have any trackers should automatically advance
each package to the latest available version without calling any migrate() functions.
"""
# Make sure we start out with a clean slate
self.assertEquals(MigrationTracker.get_collection().find({}).count(), 0)
# Make sure that our mock works. There are three valid packages.
self.assertEquals(len(models.get_migration_packages()), 4)
manage.main()
# No calls to apply_migration should have been made, and we should be at the latest package
# versions for each of the packages that have valid migrations.
self.assertFalse(mocked_apply_migration.called)
for package in models.get_migration_packages():
self.assertEqual(package.current_version, package.latest_available_version)
# Calling main() again should still not call apply_migration() or change the versions
manage.main()
self.assertFalse(mocked_apply_migration.called)
for package in models.get_migration_packages():
self.assertEqual(package.current_version, package.latest_available_version)
def test_save(self):
# Make sure we are starting off clean
self.assertEquals(MigrationTracker.get_collection().find({}).count(),
0)
# Instantiate a MigrationTracker
mt = MigrationTracker('meaning_of_life', 41)
# At this point there should not be a MigrationTracker in the database
self.assertEquals(mt._collection.find({}).count(), 0)
# saving the mt should add it to the DB
mt.save()
self.assertEquals(mt._collection.find({}).count(), 1)
mt_bson = mt._collection.find_one({'name': 'meaning_of_life'})
self.assertEquals(mt_bson['name'], 'meaning_of_life')
self.assertEquals(mt_bson['version'], 41)
# now let's update the version to 42, the correct meaning of life
mt.version = 42
mt.save()
# see if the updated meaning of life made it to the DB
self.assertEquals(mt._collection.find({}).count(), 1)
mt_bson = mt._collection.find_one({'name': 'meaning_of_life'})
self.assertEquals(mt_bson['name'], 'meaning_of_life')
self.assertEquals(mt_bson['version'], 42)
def test_migrate_with_test_flag(self, start_logging_mock, mocked_apply_migration, mocked_stdout,
mocked_stderr):
"""
Let's set all the packages to be at version 0, and then check that the migrations get called
in the correct order. We will also set the --test flag and ensure that the migration
versions do not get updated.
"""
# Make sure we start out with a clean slate
self.assertEquals(MigrationTracker.get_collection().find({}).count(), 0)
# Make sure that our mock works. There are three valid packages.
self.assertEquals(len(models.get_migration_packages()), 4)
# Set all versions back to 0
for package in models.get_migration_packages():
package._migration_tracker.version = 0
package._migration_tracker.save()
manage.main()
# There should have been a print to stderr about the Exception
expected_stderr_calls = [
('Applying migration unit.server.db.migration_packages.raise_exception.0002_oh_no '
'failed.\n\nHalting migrations due to a migration failure.'), ' ', ' See log for details.', '\n',
'Bet you didn\'t see this coming.', '\n']
stderr_calls = [mock_call[1][0] for mock_call in mocked_stderr.mock_calls]
self.assertEquals(stderr_calls, expected_stderr_calls)
migration_modules_called = [
mock_call[1][1].name for mock_call in mocked_apply_migration.mock_calls]
# Note that none of the migrations that don't meet our criteria show up in this list. Also,
# Note that migration_packages.raise_exception.0003_shouldnt_run doesn't appear
# since migration_packages.raise_exception.0002_oh_no raised an Exception. Note
# also that even though the raise_exception package raised an Exception, we still run all
# the z migrations because we don't want one package to break another.
expected_migration_modules_called = [
'unit.server.db.migration_packages.platform.0001_stuff_and_junk',
'unit.server.db.migration_packages.raise_exception.0001_works_fine',
'unit.server.db.migration_packages.raise_exception.0002_oh_no']
self.assertEquals(migration_modules_called, expected_migration_modules_called)
# Assert that our precious versions have not been updated, since we have the --test flag
for package in models.get_migration_packages():
self.assertEqual(package.current_version, 0)
def test_migrate_with_dry_run_flag(self, mock_file_config, mocked_apply_migration, getLogger):
"""
Test that when a dry run is performed, no migrations actually occur.
"""
logger = MagicMock()
getLogger.return_value = logger
# Make sure we start out with a clean slate
self.assertEquals(MigrationTracker.get_collection().find({}).count(), 0)
# Make sure that our mock works. There are three valid packages.
self.assertEquals(len(models.get_migration_packages()), 4)
# Set all versions back to 0
for package in models.get_migration_packages():
package._migration_tracker.version = 0
package._migration_tracker.save()
result = manage.main()
# Test that none of the mock objects were actually called
migration_modules_called = [
mock_call[1][1].name for mock_call in mocked_apply_migration.mock_calls]
self.assertEquals(0, len(migration_modules_called))
self.assertEquals(1, result)
for package in models.get_migration_packages():
self.assertEqual(package.current_version, 0)
def clean(self):
super(MigrationTest, self).clean()
# Make sure each test doesn't have any lingering MigrationTrackers
MigrationTracker.get_collection().remove({})
def test___init__(self):
self.assertEquals(self.mtm._collection, MigrationTracker.get_collection())
def __init__(self):
self._collection = MigrationTracker.get_collection()
def clean(self):
super(MigrationTest, self).clean()
# Make sure each test doesn't have any lingering MigrationTrackers
MigrationTracker.get_collection().remove({})
def test___init__(self):
mt = MigrationTracker('meaning_of_life', 42)
self.assertEquals(mt.name, 'meaning_of_life')
self.assertEquals(mt.version, 42)
self.assertEquals(mt._collection, MigrationTracker.get_collection())
def test___init__(self):
mt = MigrationTracker('meaning_of_life', 42)
self.assertEquals(mt.name, 'meaning_of_life')
self.assertEquals(mt.version, 42)
self.assertEquals(mt._collection, MigrationTracker.get_collection())
def test___init__(self):
self.assertEquals(self.mtm._collection,
MigrationTracker.get_collection())
def __init__(self):
self._collection = MigrationTracker.get_collection()
