Would Planet Nine pass the planet test?
Although Planet Nine has not been detected, many people have asked whether it would qualify as a planet. Using the theoretical estimates of the orbit and mass of the putative planet (Batygin and Brown 2016), it is possible to show that it satisfies a quantitative criterion for orbit-clearing (Margot 2015). According to this criterion, Planet Nine will qualify as a planet, if and when it is detected.
For further reading