test_autotb - generate simple test benches

yosys> help test_autotb
test_autotb [options] [filename]
Automatically create primitive Verilog test benches for all modules in the
design. The generated testbenches toggle the input pins of the module in
a semi-random manner and dumps the resulting output signals.

This can be used to check the synthesis results for simple circuits by
comparing the testbench output for the input files and the synthesis results.

The backend automatically detects clock signals. Additionally a signal can
be forced to be interpreted as clock signal by setting the attribute
'gentb_clock' on the signal.

The attribute 'gentb_constant' can be used to force a signal to a constant
value after initialization. This can e.g. be used to force a reset signal
low in order to explore more inner states in a state machine.

The attribute 'gentb_skip' can be attached to modules to suppress testbench
-n <int>
number of iterations the test bench should run (default = 1000)
-seed <int>
seed used for pseudo-random number generation (default = 0).
a value of 0 will cause an arbitrary seed to be chosen, based on
the current system time.