diff --git a/tests/test_cycling.py b/tests/test_cycling.py
index 13435d8..0ee7a89 100644
--- a/tests/test_cycling.py
+++ b/tests/test_cycling.py
@@ -6,6 +6,12 @@
 
 class TestParseCyclingTCX(TestCase):
     def setUp(self):
+        """
+        TCX file test2.tcx was taken from the following dataset:
+        S. Rauter, I. Jr. Fister, I. Fister. A collection of sport activity files
+        for data analysis and data mining.
+        Technical report 0201, University of Ljubljana and University of Maribor, 2015.
+        """
         tcx_file = "test2.tcx"
         path = os.path.join(os.path.dirname(__file__), "files", tcx_file)
         self.tcx = TCXParser(path)