Install Icarus Verilog from Homebrew.
cd into the downloaded folder, then cd mips, then run:
iverilog -o testbench multi.v alu.v clock.v controlunit.v enregister.v memory.v register.v registerfile.v shiftleft2.v shiftleft2preserve.v signextend.v
Then run vvp testbench.
It will start outputting memory at each clock edge, then crash.