I think that the Testbench generator tools may not meet the requirement of designer. Because the spec.'s understanding for a software is very difficult.
the code coverage of verification may not meet the requirement.
If all conditions are met in the testbench, that is very time-consuming.
This reply is for those who will be reading this thread ...
You can find/download free VHDL, Verilog testbench
generators from **broken link removed**
Other free utilities available in this site are,
Verilog netlist parser, RTL uniquifier. All these utilities
are platform independent ( Windows, Linux, Solaris ) as
these are implemented in Java.