Macro assert_ref_counts 

macro_rules! assert_ref_counts {
    ($edge:ident = $count:literal) => { ... };
    ($edge:ident, $($edges:ident),+ = $count:literal) => { ... };
    ($($edges:ident),+ = $count:literal; $($($edgess:ident),+ = $counts:literal);+) => { ... };
}

Assert that the reference counts of edges match

Example

let e1 = DummyEdge::new();
let e2 = DummyManager.clone_edge(&e1);
let e3 = DummyEdge::new();
assert_ref_counts!(e1, e2 = 2; e3 = 1);