diff --git a/tests/test_utils.py b/tests/test_utils.py
new file mode 100644
index 00000000..85ed54ae
--- /dev/null
+++ b/tests/test_utils.py
@@ -0,0 +1,42 @@
+import pytest
+from llm.utils import simplify_usage_dict
+
+
+@pytest.mark.parametrize(
+    "input_data,expected_output",
+    [
+        (
+            {
+                "prompt_tokens_details": {"cached_tokens": 0, "audio_tokens": 0},
+                "completion_tokens_details": {
+                    "reasoning_tokens": 0,
+                    "audio_tokens": 1,
+                    "accepted_prediction_tokens": 0,
+                    "rejected_prediction_tokens": 0,
+                },
+            },
+            {"completion_tokens_details": {"audio_tokens": 1}},
+        ),
+        (
+            {
+                "details": {"tokens": 5, "audio_tokens": 2},
+                "more_details": {"accepted_tokens": 3},
+            },
+            {
+                "details": {"tokens": 5, "audio_tokens": 2},
+                "more_details": {"accepted_tokens": 3},
+            },
+        ),
+        ({"details": {"tokens": 0, "audio_tokens": 0}, "more_details": {}}, {}),
+        ({"level1": {"level2": {"value": 0, "another_value": {}}}}, {}),
+        (
+            {
+                "level1": {"level2": {"value": 0, "another_value": 1}},
+                "level3": {"empty_dict": {}, "valid_token": 10},
+            },
+            {"level1": {"level2": {"another_value": 1}}, "level3": {"valid_token": 10}},
+        ),
+    ],
+)
+def test_simplify_usage_dict(input_data, expected_output):
+    assert simplify_usage_dict(input_data) == expected_output