Positive coverage: all_even / all_even

2 tests exercised this rule:

Source location: crates/formality-core/src/judgment/test_for_all.rs:37

#[test]
fn test_for_all_success() {
    let nums = vec![Num(2), Num(4), Num(6)];
    all_even(nums).assert_ok(expect_test::expect!["{()}"]);
}

Source location: crates/formality-core/src/judgment/test_for_all.rs:51

#[test]
fn test_for_all_empty() {
    let nums: Vec<Num> = vec![];
    all_even(nums).assert_ok(expect_test::expect!["{()}"]);
}