As discussed in golang/go#26109, vet typecheck is enabled
in go1.11 and the command_test.go can't be compiled any
more with go1.11 due to the unread variables in the
command_test.go.
Instead of removing the unused variables, this CL reads the
variables and compares the values against the current
behavior so when the related issue is fixed, this test can
be updated accordingly.
