func TestProcess(t *testing.T, s ...string) {
	h := &ExternalTokenHelper{BinaryPath: TestProcessPath(t, s...)}
	Test(t, h)
}
TestProcess is used to re-execute this test in order to use it as the
helper process. For this to work, the TestExternalTokenHelperProcess function must
exist.
package token
import (
	"fmt"
	"os"
	"strings"
	"testing"
	"github.com/mitchellh/cli"
)
func Test(t *testing.T, h TokenHelper) {
	if err := h.Store("foo"); err != nil {
		t.Fatalf("err: %s", err)
	}
	v, err := h.Get()
	if err != nil {
		t.Fatalf("err: %s", err)
	}
	if v != "foo" {
		t.Fatalf("bad: %#v", v)
	}
	if err := h.Erase(); err != nil {
		t.Fatalf("err: %s", err)
	}
	v, err = h.Get()
	if err != nil {
		t.Fatalf("err: %s", err)
	}
	if v != "" {
		t.Fatalf("bad: %#v", v)
	}
}