Add visualization test

Author: zStupan

niaarm/tests/test_data/README.md

@@ -3,3 +3,5 @@
 - The Abalone dataset is downloaded from https://archive.ics.uci.edu/ml/index.php.
 
 - The wiki_test_case dataset is composed from the first Table found in: https://en.wikipedia.org/wiki/Lift_(data_mining)
+
+- SpotyDataGen - Iztok Fister Jr., Grega Vrbančič, Lucija Brezočnik, Vili Podgorelec, Iztok Fister. [SportyDataGen: an online generator of endurance sports activity collections](http://iztok-jr-fister.eu/static/publications/225.pdf). In: CECIIS: Central European Conference on Information and Intelligent Systems, pp. 171-178, 2018.