void TextProcessorTester::testExtensionSubtable()
{
    Builder builder;

    /* Test with an unmatching glyph. */
    testSubstitution(builder.createExtension(LookupType::sSingle, builder.createSingleSubst({ 1 }, 100)),
                     { 0 }, { 0 });
    /* Test with a matching glyph.*/
    testSubstitution(builder.createExtension(LookupType::sSingle, builder.createSingleSubst({ 1 }, 100)),
                     { 1 }, { 101 });
}