invalid_value('letter-spacing', value);
}

// Syntax checking
test_invalid_number('progress()');
test_invalid_number('progress( )');
test_invalid_number('progress(,)');
test_invalid_number('progress(1, )');
test_invalid_number('progress(1)');
test_invalid_number('progress(50%, 0)');
test_invalid_number('progress(0, 1,)');
test_invalid_number('progress(from,)');
test_invalid_number('progress(from 1, 0)');
test_invalid_number('progress(from 1, 0 1)');
test_invalid_number('progress(from 1 0)');
test_invalid_nu