.DeleteRange([]byte("foo"), nil)   if n != 0 || rev != base+0 {    t.Errorf("#%d: n = %d, rev = %d, want (%d, %d)", i, n, rev, 0, base+0)   }    r, err = s.Range([]byte("foo"), nil, RangeOptions{Rev: base + 0})   if err != nil {    t.Fatal(err)   }   if r.KVs != nil {    t.Errorf("#%d: kvs = %+v, want %+v", i, r.KVs, nil)   }   if r.Rev != base+0 {    t.Errorf("#%d: range rev = %d, want %d", i, r.Rev, base+0)   }  