Use APKPure App
Get OPO Charging Current old version APK for Android
Monitor the charging current of your OnePlus One
RealTime monitor of the charging current of your One Plus One
Just plug the charger, and chech the current in mA
Is your One Plus One charging or discharging ?
Open the application and if it is above 850 mA, means your charger is working correctly.
Open the Raw Info and you can check your battery info, like battery type, voltage etc
Enjoy
Note: This software has only been tested on OnePlus One