How to fuzz rustybuzz?

[qarmin]

For now I'm using this code

fn check_file(path: &str) {
    let data = std::fs::read(path).unwrap();
    let _ = process_face(&data);
}
fn process_face(data: &[u8]) -> Option<()> {
    let face =  rustybuzz::Face::from_slice(data, 0)?;
    let buffer = rustybuzz::UnicodeBuffer::new();
    rustybuzz::shape(&face, &[], buffer);
    let mut buffer = rustybuzz::UnicodeBuffer::new();
    buffer.push_str("fi");
    rustybuzz::shape(&face, &[], buffer);
    let mut buffer = rustybuzz::UnicodeBuffer::new();
    buffer.push_str("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFfASFAMFIQAWNFWOIQBFOBFOABFOBAWOFBQWOFBOABFOASBOFBASOFBOASBFOIAWBOFBQWOFBOAWBFOIAWBFOAWBFOAWBODBAWODNQWOFBQOWBFOABFOAWBODBAOWWAOFBNOQWTGPOQWNGFPOWQNBFDOQWNFONQWDFNASODNBAWOBDFWQOFBNQWODOQWFNBOQWBNFOWAF");
    rustybuzz::shape(&face, &[], buffer);
    let mut buffer = rustybuzz::UnicodeBuffer::new();
    buffer.push_str("ĄĆŹŻĆŒĆŁΩŒ™ΩŒ™ΩŒ® ̵ŁŁ®Ω¡¿®¡˝¿∧¡×¿£∧ס¿¼¡—®ÞŁ¡¿¡¿™GŒÐΩŒÐÞΩŒÆŊ ̵ΩŒŊ°ÞΩ¡Ff");
    rustybuzz::shape(&face, &[], buffer);
    Some(())
}

[LaurenzV]

I'm not sure what kind of answer you are expecting... How to fuzz depends on what exactly you want to fuzz, there are many different approaches. Maybe you could elaborate a bit or specify what problem you are facing?

[qarmin]

This code tests only converting fonts from file and rendering characters.
Is there any other component that could be tested in this way(as input I have only valid/unvalid font file)?

[LaurenzV]

I guess that's the main thing to test then. But you could try things like enabling certain features, variation coordinates for variables fonts, changing the test direction, etc.