message: this test is slow because it runs the same searches repeatedly
diff: @@ -468,6 +468,34 @@ fn resolving_with_constrained_sibling_backtrack_parent() {
  ("constrained", "1.0.0")])));
  }
  +#[test]
  +fn resolving_with_many_equivalent_backtracking() {
  + let mut reglist = vec![
  + pkg!(("level0", "1.0.0")),
  + ];
  +
  + const DEPTH: usize = 10;
  + const BRANCHING_FACTOR: usize = 5;
  +
  + for l in 0..DEPTH {
  + let name = format!("level{}", l);
  + let next = format!("level{}", l + 1);
  + for i in 1..BRANCHING_FACTOR {
  + let vsn = format!("1.0.{}", i);
  + reglist.push(pkg!((name.as_str(), vsn.as_str()) => [dep_req(next.as_str(), "*")]));
  + }
  + }
  +
  + let reg = registry(reglist);
  +
  + let res = resolve(&pkg_id("root"), vec![
  + dep_req("level0", "*"),
  + ], &reg).unwrap();
  +
  + assert_that(&res, contains(names(&[("root", "1.0.0"),
  + ("level0", "1.0.0")])));
  +}
  +
  #[test]
  fn resolving_with_constrained_sibling_backtrack_activation() {
  // It makes sense to resolve most-constrained deps first, but
  