Kon-Boot has updated to support macOS Sierra systems, allowing you to login into the system without knowing the previous passwords/user names. By virtually modifying the EFI bios and then modifying parts of the kernel. The changes are only made in virtual memory and they disappear after reboot. Kon-Boot allows you to either login into selected account without knowing the password (bypass mode) or it will create new “root” account for you (new-account mode) from which you will be able to change other users passwords as needed.
You can purchase the license here: http://thelead82.com/products-mac.html
Or get the 2in1 version which allows you to bypass Windows XP through 10 passwords as well: http://thelead82.com/products-2in1.html
As a RepairTechnician or Penetration Tester this product is well worth the money for the time you save.