I am quite new with timeseries and in my understanding I perceive some contradictions in KPSS and ADF tests combined.
Using this timeseries when performing ADF and KPSS I could interpret
KPSS: The timeseries fails to reject the null hypothesis of stationarity (wtf? how can this timeseries be stationary if it clearly has a tendency upwards?)
ADF: Can't reject tau (at 1%) and therefore there is a unit root, reject phi2 and therefore there must be drift, trend or both. Can't reject phi3 and this time series would be a randomwalk with drift.
How can this timeseries be stationary and have a unit root?