tests/journal_lock.py: Initial framework.

No actual test per se yet, but this runs with `pytest -k 'journal_lock'`

tests/journal_lock.py/test_journal_lock.py

@@ -0,0 +1,57 @@
+"""Tests for journal_lock.py code."""
+# Tests:
+#  - Need logging set up, at TRACE level.
+#
+#  - Will need to mock config for the retrieval of journaldir.
+#  - Can ask pytest to create a unique tmp dir:
+#
+#       <https://docs.pytest.org/en/stable/getting-started.html#request-a-unique-temporary-directory-for-functional-tests>
+#
+#  - Is file actually locked after obtain_lock().  Problem: We opened the
+#     file in a manner which means nothing else can open it.  Also I assume
+#     that the same process will either be allowed to lock it 'again' or
+#     overwrite the lock.
+#
+#     Expected failures if:
+#
+#      1. Lock already held (elsewhere).
+#      2. Can't open lock file 'w+'.
+#      3. Path to lock file doesn't exist.
+#      4. journaldir is None (default on Linux).
+#
+#  - Does release_lock() work?  Easier to test, if it's worked....
+#      1. return True if not locked.
+#      2. return True if locked, but successful unlock.
+#      3. return False otherwise.
+#
+#  - JournalLock.set_path_from_journaldir
+#      1. When journaldir is None.
+#      2. Succeeds otherwise?
+#
+#  - Can any string to pathlib.Path result in an invalid path for other
+#    operations?
+#
+#  - Not sure about testing JournalAlreadyLocked class.
+
+from pytest._pytest import monkeypatch, tmpdir
+
+from config import config
+from journal_lock import JournalLock
+
+
+def test_journal_lock_init(monkeypatch: monkeypatch, tmpdir: tmpdir):  # type: ignore
+    """Test JournalLock instantiation."""
+
+    def get_str(key: str, *, default: str = None) -> str:
+        """Mock config.*Config get_str to provide fake journaldir."""
+        if key == 'journaldir':
+            print('journaldir: using tmpdir')
+            return tmpdir
+
+        print('Other key, calling up ...')
+        return config.get_str(key)  # Call the non-mocked
+
+    with monkeypatch.context() as m:
+        m.setattr(config, "get_str", get_str)
+        print(f'{tmpdir=}')
+        jlock = JournalLock()