env GO111MODULE=off

# go test -c -o NUL
# should work (see golang.org/issue/28035).
cd x
go test -o=$devnull -c
! exists x.test$GOEXE

-- x/x_test.go --
package x_test
import (
    "testing"
)
func TestNUL(t *testing.T) {
}
