diff --git a/src/harmonization_framework/replay_log/replay_logger.py b/src/harmonization_framework/replay_log/replay_logger.py
index 4361398..fd93845 100644
--- a/src/harmonization_framework/replay_log/replay_logger.py
+++ b/src/harmonization_framework/replay_log/replay_logger.py
@@ -9,6 +9,14 @@ class Event:
     dataset: str
 
     def to_log(self):
+        """
+        Serialize an event to a JSON-compatible dict.
+
+        Returns:
+            dict with keys:
+            - action: serialized harmonization rule
+            - dataset: dataset identifier
+        """
         log = {
             "action": self.action.serialize(),
             "dataset": self.dataset,
@@ -16,6 +24,19 @@ def to_log(self):
         return log
 
 def _get_log_level(level: int):
+    """
+    Map a numeric log level to a logging module constant.
+
+    Args:
+        level: integer in the range 1-4.
+            1 -> CRITICAL
+            2 -> ERROR
+            3 -> INFO
+            4 -> DEBUG
+
+    Returns:
+        A logging level constant.
+    """
     match level:
         case 1:
             return logging.CRITICAL
@@ -29,9 +50,22 @@ def _get_log_level(level: int):
             return ValueError(f"Invalid log level: {level}")
 
 def configure_logger(level: int, log_file: str):
+    """
+    Configure a replay logger that writes JSON lines to a file.
+
+    Args:
+        level: integer log level (1-4).
+        log_file: path to the output log file.
+
+    Returns:
+        A configured logger instance.
+    """
     # create logger
     logger = logging.getLogger("ReplayLogger")
 
+    # clear any existing handlers to avoid duplicate log entries
+    logger.handlers.clear()
+
     # set logging level
     log_level = _get_log_level(level)
     logger.setLevel(log_level)
@@ -48,5 +82,8 @@ def configure_logger(level: int, log_file: str):
     return logger
 
 def log_operation(logger, action, dataset):
+    """
+    Log a single replay event for a given harmonization action and dataset.
+    """
     event = Event(action, dataset)
     logger.info(json.dumps(event.to_log()))
diff --git a/tests/test_replay_logger.py b/tests/test_replay_logger.py
new file mode 100644
index 0000000..b7859ce
--- /dev/null
+++ b/tests/test_replay_logger.py
@@ -0,0 +1,20 @@
+import logging
+
+from harmonization_framework.replay_log import replay_logger as rlog
+
+
+def test_configure_logger_clears_handlers(tmp_path):
+    log1 = tmp_path / "log1.jsonl"
+    log2 = tmp_path / "log2.jsonl"
+
+    logger1 = rlog.configure_logger(3, str(log1))
+    assert len(logger1.handlers) == 1
+
+    logger2 = rlog.configure_logger(3, str(log2))
+    assert logger2 is logger1
+    assert len(logger2.handlers) == 1
+
+    # Ensure the active handler points to the most recent log file
+    handler = logger2.handlers[0]
+    assert isinstance(handler, logging.FileHandler)
+    assert handler.baseFilename == str(log2)