Hong and Ladner used context-based group testing to implement bit-plane coding for image compression. We extend this technique to video coding, by replacing the quantization and entropy-coding stages, of an H.263 standard video coder, with bit-plane coding. We experiment with ways to improve baseline coder, including different classification schemes and cross-frame adaptive coding. Our results indicate that our new coder, GTV (Group Testing for Video), significantly outperforms H.263 at medium to high bit-rates (300+ kbps) on most sequences, while allowing very precise rate scalability.