Add test to PVForecast (#174)

* Add documentation to class_pv_forecast.py.

Added documentation. Beware mostly generated by ChatGPT.

Signed-off-by: Bobby Noelte <b0661n0e17e@gmail.com>

* Add CacheFileStore, datetime and logger utilities.

The `CacheFileStore` class is a singleton-based, thread-safe key-value store for managing
temporary file objects, allowing the creation, retrieval, and management of cache files.

The utility modules offer a flexible logging setup (`get_logger`) and utilities to handle
different date-time formats (`to_datetime`, `to_timestamp`) and timezone detection
(`to_timezone).

- Cache files are automatically valid for the the current date unless specified otherwise.
  This is to mimic the current behaviour used in several classes.
- The logger supports rotating log files to prevent excessive log file size.
- The `to_datetime` and `to_timestamp`functions support a wide variety of input types and formats.
  They provide the time conversion that is e.g. used in PVForecast.

Signed-off-by: Bobby Noelte <b0661n0e17e@gmail.com>

* Improve testability of PVForecast

Improvements for testing of PVForecast
- Use common utility functions to allow for general testing at one spot.
  - to_datetime
  - CacheFileStore
- Use logging instead of print to easily capture in testing.
- Add validation of the json schema for Akkudoktor PV forecast data.
- Allow to create an empty PVForecast instance as base instance for testing.
- Make process_data() complete for filling a PVForecast instance for testing.
- Normalize forecast datetime to timezone of system given in loaded data.
- Do not print report but provide report for test checks.
- Get rid of cache file path using the CachFileStore to automate cache file usage.
- Improved module documentation.

Signed-off-by: Bobby Noelte <b0661n0e17e@gmail.com>

* Add test for PVForecast and newly extracted utility modules.

- Add test for PVForecast
- Add test for CacheFileStore in the new cachefilestore module
- Add test for to_datetime, to_timestamp, to_timezone in the new
  datetimeutil module
- Add test for get_logger in the new logutil module

Signed-off-by: Bobby Noelte <b0661n0e17e@gmail.com>

---------

Signed-off-by: Bobby Noelte <b0661n0e17e@gmail.com>
Co-authored-by: Normann <github@koldrack.com>

tests/conftest.py

@@ -1,11 +1,22 @@
+import logging
 import os
 import subprocess
 import sys
+import time
 
 import pytest
 from xprocess import ProcessStarter
 
 
+@pytest.fixture(autouse=True)
+def disable_debug_logging():
+    # Temporarily set logging level higher than DEBUG
+    logging.disable(logging.DEBUG)
+    yield
+    # Re-enable logging back to its original state after the test
+    logging.disable(logging.NOTSET)
+
+
 def pytest_addoption(parser):
     parser.addoption(
         "--full-run", action="store_true", default=False, help="Run with all optimization tests."
@@ -19,6 +30,11 @@ def is_full_run(request):
 
 @pytest.fixture
 def server(xprocess):
+    """Fixture to start the server.
+
+    Provides URL of the server.
+    """
+
     class Starter(ProcessStarter):
         # assure server to be installed
         try:
@@ -62,3 +78,29 @@ def server(xprocess):
 
     # clean up whole process tree afterwards
     xprocess.getinfo("akkudoktoreosserver").terminate()
+
+
+@pytest.fixture
+def other_timezone():
+    """Fixture to temporarily change the timezone.
+
+    Restores the original timezone after the test.
+    """
+    original_tz = os.environ.get("TZ", None)
+
+    other_tz = "Atlantic/Canary"
+    if original_tz == other_tz:
+        other_tz = "Asia/Singapore"
+
+    # Change the timezone to another
+    os.environ["TZ"] = other_tz
+    time.tzset()  # For Unix/Linux to apply the timezone change
+
+    yield os.environ["TZ"]  # Yield control back to the test case
+
+    # Restore the original timezone after the test
+    if original_tz:
+        os.environ["TZ"] = original_tz
+    else:
+        del os.environ["TZ"]
+    time.tzset()  # Re-apply the original timezone