We also need to know how to save the generated test cases, of type Vec<Operation<T>>, to the file system.

The easiest way to do that is to use serde and its derive macros Serialize and Deserialize.

use serde::{Serialize, Deserialize};

#[derive(Clone, DefaultMutator, Serialize, Deserialize)]
enum Operation<T: Ord> {

Then, we will provide a fuzzcheck::SerdeSerializer to our fuzz test so that each interesting Vec<Operation<T>> is saved as a JSON file.

There are other ways to serialize test cases. For example, for values of type Vec<u8>, you can use a fuzzcheck::ByteSerializer, which will simply copy the content of the vector to the file system. For values of type String, one can use a fuzzcheck::StringSerializer.