loader.mercurial: Increase coverage

As per my suggestion [1], transformed the loader verifier code into tests.

• loader_verifier: Transform the verifier into tests

• tests_tasks: Add scenario to check tasks are fine

• test_converters: Add coverage on converters

• Add scenario for archive mercurial loader (success + failure)

• [1] https://forge.softwareheritage.org/swh/devel/swh-environment#1411

Related swh-environment#1411 (closed) Related T1439 Related swh-environment#1443 (closed)

Test Plan

tox

---

Migrated from D802 (view on Phabricator)

swh/loader/mercurial/tests/common.py

+# Copyright (C) 2018  The Software Heritage developers
+# See the AUTHORS file at the top-level directory of this distribution
+# License: GNU General Public License version 3, or any later version
+# See top-level LICENSE file for more information
+
+from swh.loader.mercurial.loader import (
+    HgBundle20Loader, HgArchiveBundle20Loader
+)
+
+
+_LOADER_TEST_CONFIG = {
+    'bundle_filename': 'HG20_none_bundle',
+    'cache1_size': 838860800,
+    'cache2_size': 838860800,
+    'content_packet_size': 100000,
+    'content_packet_size_bytes': 1073741824,
+    'content_size_limit': 104857600,
+    'directory_packet_size': 25000,
+    'log_db': 'dbname=softwareheritage-log',
+    'occurrence_packet_size': 100000,
+    'reduce_effort': False,
+    'release_packet_size': 100000,
+    'revision_packet_size': 100000,
+    'save_data': False,
+    'save_data_path': '',
+    'send_contents': True,
+    'send_directories': True,
+    'send_occurrences': True,
+    'send_releases': True,
+    'send_revisions': True,
+    'send_snapshot': True,
+    'storage': {'args': {}, 'cls': 'memory'},
+    'temp_directory': '/tmp/swh.loader.mercurial'
+}
+
+
+class BaseHgLoaderMemoryStorage:
+    """The base mercurial loader to test.
+
+     Mixin behavior changed to:
+    - use an in-memory storage
+    - not use the default configuration loading mechanism
+
+    At the end of the tests, you can make sure you have the rights
+    objects.
+
+    """
+    def __init__(self):
+        super().__init__()
+        self.origin_id = 1
+        self.visit = 1
+
+    def parse_config_file(self, *args, **kwargs):
+        return _LOADER_TEST_CONFIG
+
+
+class HgLoaderMemoryStorage(BaseHgLoaderMemoryStorage, HgBundle20Loader):
+    pass
+
+
+class HgArchiveLoaderMemoryStorage(BaseHgLoaderMemoryStorage,
+                                   HgArchiveBundle20Loader):
+    pass