diff --git a/tests/copilot_usage/test_logging_config.py b/tests/copilot_usage/test_logging_config.py
new file mode 100644
index 0000000..fd9cbde
--- /dev/null
+++ b/tests/copilot_usage/test_logging_config.py
@@ -0,0 +1,90 @@
+"""Tests for copilot_usage.logging_config — setup_logging, _emoji_patcher, LEVEL_EMOJI."""
+
+# pyright: reportPrivateUsage=false
+# pyright: reportUnknownMemberType=false
+# pyright: reportAttributeAccessIssue=false
+# pyright: reportUnknownVariableType=false
+# pyright: reportUnknownArgumentType=false
+
+from __future__ import annotations
+
+import sys
+
+from loguru import logger
+
+from copilot_usage.logging_config import (
+    LEVEL_EMOJI,
+    _emoji_patcher,
+    setup_logging,
+)
+
+# ---------------------------------------------------------------------------
+# setup_logging
+# ---------------------------------------------------------------------------
+
+
+def test_setup_logging_adds_exactly_one_sink() -> None:
+    """After setup_logging(), logger has exactly one handler."""
+    setup_logging()
+    assert len(logger._core.handlers) == 1
+
+
+def test_setup_logging_idempotent() -> None:
+    """Calling setup_logging() twice still results in exactly 1 sink."""
+    setup_logging()
+    setup_logging()
+    assert len(logger._core.handlers) == 1
+
+
+def test_setup_logging_targets_stderr() -> None:
+    """After setup_logging(), the single sink targets sys.stderr."""
+    setup_logging()
+    handler = next(iter(logger._core.handlers.values()))
+    assert handler._sink._stream is sys.stderr
+
+
+def test_setup_logging_level_is_warning() -> None:
+    """After setup_logging(), the minimum log level is WARNING."""
+    setup_logging()
+    handler = next(iter(logger._core.handlers.values()))
+    assert handler.levelno == logger.level("WARNING").no
+
+
+# ---------------------------------------------------------------------------
+# _emoji_patcher
+# ---------------------------------------------------------------------------
+
+
+def test_emoji_patcher_known_levels() -> None:
+    """_emoji_patcher sets record['extra']['emoji'] for each known level."""
+    for level_name, expected_emoji in LEVEL_EMOJI.items():
+        record: dict[str, object] = {
+            "level": type("Level", (), {"name": level_name})(),
+            "extra": {},
+        }
+        _emoji_patcher(record)  # type: ignore[arg-type]
+        assert record["extra"]["emoji"] == expected_emoji  # type: ignore[index]
+
+
+def test_emoji_patcher_unknown_level_fallback() -> None:
+    """_emoji_patcher falls back to '  ' for an unknown level name."""
+    record: dict[str, object] = {
+        "level": type("Level", (), {"name": "NONEXISTENT"})(),
+        "extra": {},
+    }
+    _emoji_patcher(record)  # type: ignore[arg-type]
+    assert record["extra"]["emoji"] == "  "  # type: ignore[index]
+
+
+# ---------------------------------------------------------------------------
+# LEVEL_EMOJI
+# ---------------------------------------------------------------------------
+
+_STANDARD_LEVELS = frozenset(
+    {"TRACE", "DEBUG", "INFO", "SUCCESS", "WARNING", "ERROR", "CRITICAL"}
+)
+
+
+def test_level_emoji_covers_all_standard_levels() -> None:
+    """LEVEL_EMOJI contains entries for all seven standard loguru levels."""
+    assert _STANDARD_LEVELS.issubset(LEVEL_EMOJI.keys())