test: add unit tests for log.configure options

Add comprehensive unit tests for `enapter.log.configure` to verify that
correct logging handlers, formatting, and levels are properly configured
for different arguments (`level=None`, integer and string level names,
and custom streams).

Co-authored-by: rnovatorov <20299819+rnovatorov@users.noreply.github.com>

Author: google-labs-jules[bot]

tests/unit/test_log/test_init.py

@@ -0,0 +1,37 @@
+import io
+import logging
+
+import enapter
+
+
+def test_configure_level_none():
+    enapter.log.configure(level=None)
+    assert len(enapter.log.LOGGER.handlers) == 1
+    assert isinstance(enapter.log.LOGGER.handlers[0], logging.NullHandler)
+
+
+def test_configure_level_str():
+    enapter.log.configure(level="DEBUG")
+    assert enapter.log.LOGGER.level == logging.DEBUG
+    assert len(enapter.log.LOGGER.handlers) == 1
+    handler = enapter.log.LOGGER.handlers[0]
+    assert isinstance(handler, logging.StreamHandler)
+    assert isinstance(handler.formatter, enapter.log.JSONFormatter)
+
+
+def test_configure_level_int():
+    enapter.log.configure(level=logging.INFO)
+    assert enapter.log.LOGGER.level == logging.INFO
+    assert len(enapter.log.LOGGER.handlers) == 1
+    handler = enapter.log.LOGGER.handlers[0]
+    assert isinstance(handler, logging.StreamHandler)
+    assert isinstance(handler.formatter, enapter.log.JSONFormatter)
+
+
+def test_configure_custom_stream():
+    stream = io.StringIO()
+    enapter.log.configure(level=logging.INFO, stream=stream)
+    assert len(enapter.log.LOGGER.handlers) == 1
+    handler = enapter.log.LOGGER.handlers[0]
+    assert isinstance(handler, logging.StreamHandler)
+    assert handler.stream is stream