If you are someone like me, who suddenly started using the Xilinx Vivado tool after using Xilinx ISE for a long time, then you might have noticed that Vivado currently doesn't support the Automatic testbench generation.
This is such a major disappointment for many of us. But luckily there are many online tools which does more or less the same. In this Video, I used the Doulos tool for creating testbenches for my VHDL designs. Once generated I tested the codes using the latest Vivado 2019.2 version.
Hope this is useful for you. Enjoy!