Hallie King is a girl born with a rare genetic disorder, TAR syndrome , but whose story is quite inspirational.
[youtube https://www.youtube.com/watch?v=v9DpxkhphWM&hl=en_US&fs=1&rel=0&w=400&h=300]
Testing Stationarity of a series is an activity which has to be carried out by any quant trader, irrespective of whatever the frequency of data that is being used to develop models. Hence the amount of literature on Unit Roots, is VERY HUGE.
Here is an interesting and simple way to test it. This note is refreshingly different from the usual stuff that one comes across in Unit Roots. It uses F test as a filter before going to the traditional tests.