chore: assert handlers; assert defaults create and use PT handler

Author: heitorlessa

tests/functional/test_logger.py

@@ -1193,6 +1193,7 @@ class ForeignHandler(logging.StreamHandler): ...
     assert logger.registered_handler is not foreign_handler
     assert logger.registered_handler is custom_handler
     assert logger.logger_handler is custom_handler
+    assert logger.handlers == [foreign_handler, custom_handler]
 
 
 def test_child_logger_registered_handler_is_custom_handler(service_name):
@@ -1215,6 +1216,18 @@ class ForeignHandler(logging.StreamHandler): ...
     assert child.registered_handler is parent.registered_handler
 
 
+def test_logger_handler_is_created_despite_env_pre_setup(service_name):
+    # GIVEN a library or environment pre-setup a logger for us using the same name
+    environment_handler = logging.StreamHandler()
+    logging.getLogger(service_name).addHandler(environment_handler)
+
+    # WHEN Logger init without a custom handler
+    logger = Logger(service=service_name)
+
+    # THEN registered handler should be Powertools default handler, not env
+    assert logger.registered_handler is not environment_handler
+
+
 def test_child_logger_append_keys_before_parent(stdout, service_name):
     # GIVEN a child Logger is initialized before its/without parent
     child = Logger(stream=stdout, service=service_name, child=True)