How to constraint quickcheck test argument to be non-empty in Rust

Question

I am trying to write a test which depends on non-empty vector of tuples as an argument but unsure of how to add such a constraint using quickcheck.

#[quickcheck]
fn graph_contains_vertex(vs: Vec<(u64, i64)>) {
    // ...
    let rand_index = rand::thread_rng().gen_range(0..vs.len());
    let rand_vertex = vs.get(rand_index).unwrap().0;
    // ...
}

What I am trying to do here is pick up an index from the vector passed as an argument and use first tuple value.

I ran a couple of tests and ended up with a use case where argument passed is [].

Answer 1

Apparently, we can handle invalid arguments right inside our tests like so:

#[quickcheck]
fn graph_contains_vertex(vs: Vec<(u64, i64)>) -> TestResult {
      if vs.is_empty() {
          return TestResult::discard();
      }

     // ..

      let rand_index = rand::thread_rng().gen_range(0..vs.len());
      let rand_vertex = vs.get(rand_index).unwrap().0;

      // ...

      TestResult::from_bool(g.contains(rand_vertex))
}

In this particular example, since I was depending on a non-empty vector argument, I could choose to discard the test results when received an empty vector using TestResult::discard().