why is test_bench included

Hi there,

i built a project with a part which is created with the sopc builder.

the sopc block contains a nios processor which has the name cpu_0.

when i compile my project and have a look at time quest i saw that there is a problem.

the quartus includes 2 entities which are called cpu_0_test_bench.vhd and cpu_0_oci_test_bench.vhd.

what are these files doing and why do quartus include testbench-files?

does anybody know an answer? that would be very nice!

cheers spitzinger