ffset> is not
  // equal to TEXTURE_WIDTH;
  // * <height> is not a multiple of four, and <height> plus <yoffset> is
  //           not equal to TEXTURE_HEIGHT; or
  // * <xoffset> or <yoffset> is not a multiple of four.
  ctu.testTexSubImageDimensions(gl, ext, validFormats, expectedByteLength, getBlockDimensions,
    16, 16, [
      { xoffset: 0, yoffset: 0, width: 4, height: 3,
        expectation: gl.INVALID_OPERATION, message: "height is not a multiple of 4" },
      { xoffset: 0, yoffset: 0, width: 3, 