object.
  ctu.testCompressedFormatsListed(gl, validFormats);
  ctu.testCorrectEnumValuesInExt(ext, validFormats);
  // Test that texture upload buffer size is validated correctly.
  ctu.testFormatRestrictionsOnBufferSize(gl, validFormats, expectedByteLength, getBlockDimensions);
  // Test TexSubImage validation on dimensions
  // CompressedTexSubImage* will result in an
  // INVALID_OPERATION error only if one of the following conditions occurs:
  // * <width> is not a multiple of four, and <width> plus <xo