struct S;

impl S {
    fn process(&mut self, v: usize) { }

    fn test1(&mut self) -> Result<usize, ()> {
        unimplemented!()
    }

    fn test2(&mut self) -> Result<usize, ()> {
        unimplemented!()
    }

    fn test3(&mut self) -> Result<usize, ()> {
        unimplemented!()
    }

    // ...

    fn multi(&mut self) -> Result<usize, ()> {
        let tests = [
            Self::test1,
            Self::test2,
            Self::test3,
            // ...
        ];

        for &test in &tests {
            if let Ok(v) = test(self) {
                self.process(v);
                return Ok(v);
            }
        }

        Err(())
    }
}