diff --git a/trace_export_script/tests/test_core.py b/trace_export_script/tests/test_core.py
new file mode 100644
index 0000000..63ff95f
--- /dev/null
+++ b/trace_export_script/tests/test_core.py
@@ -0,0 +1,74 @@
+import json
+import csv
+import os
+import tempfile
+import pytest
+
+from trace_export_script import core
+
+
+def _create_sample_trace_file(tmp_path):
+    data = [
+        {"timestamp": 1.0, "value": 42.5, "source": "sensor_a"},
+        {"timestamp": 2.0, "value": 43.0, "source": "sensor_b"}
+    ]
+    file_path = tmp_path / "trace_input.json"
+    with open(file_path, "w", encoding="utf-8") as f:
+        json.dump(data, f)
+    return file_path, data
+
+
+def _read_csv(file_path):
+    with open(file_path, newline="", encoding="utf-8") as csvfile:
+        reader = csv.DictReader(csvfile)
+        return list(reader)
+
+
+def test_export_to_csv(tmp_path):
+    input_file, expected_data = _create_sample_trace_file(tmp_path)
+    output_path = tmp_path / "exported_trace.csv"
+
+    # Call the function under test
+    core.export_trace_data(str(input_file), "csv")
+
+    # The function should export the CSV file in the default output directory or same dir
+    possible_files = [output_path, tmp_path / "output" / "exported_trace.csv", tmp_path / f"exported_trace.csv"]
+    exported_file = None
+    for candidate in possible_files:
+        if candidate.exists():
+            exported_file = candidate
+            break
+
+    assert exported_file is not None, "Exported CSV file not found."
+
+    rows = _read_csv(exported_file)
+    assert len(rows) == len(expected_data)
+
+    for row, expected in zip(rows, expected_data):
+        assert float(row["timestamp"]) == pytest.approx(expected["timestamp"])
+        assert float(row["value"]) == pytest.approx(expected["value"])
+        assert row["source"] == expected["source"]
+
+
+def test_export_to_json(tmp_path):
+    input_file, expected_data = _create_sample_trace_file(tmp_path)
+
+    core.export_trace_data(str(input_file), "json")
+
+    output_path = tmp_path / "output" / "exported_trace.json"
+    if not output_path.exists():
+        # Fallback: maybe in current dir
+        output_path = tmp_path / "exported_trace.json"
+
+    assert output_path.exists(), "JSON export file not found."
+
+    with open(output_path, "r", encoding="utf-8") as f:
+        data = json.load(f)
+
+    assert data == expected_data
+
+
+def test_invalid_format_raises(tmp_path):
+    input_file, _ = _create_sample_trace_file(tmp_path)
+    with pytest.raises(ValueError):
+        core.export_trace_data(str(input_file), "xml")
\ No newline at end of file