From 86cf918f8c6ef566053e5bcba66ab2ec833263bc Mon Sep 17 00:00:00 2001
From: Vittorio Distefano <info@vdistefano.studio>
Date: Thu, 5 Nov 2026 01:45:54 +0100
Subject: [PATCH] test(cvrp): score route distance so the time-window k-opt
 test can fail

The `list_cvrp_k_opt_time_window` domain had an empty constraint set, so
every route scored the same and the solve returned the initial route
whatever list k-opt construction did; the test asserting that a
time-window-breaking reversal is rejected passed with the feasibility check
removed. The domain now penalizes each route's travelled distance with the
same directed distance its problem data uses, so an applied reversal
changes the returned solution and bypassing the check fails the test.

Closes #188.
---
 .../domain/plan.rs                            | 44 +++++++++++++------
 1 file changed, 31 insertions(+), 13 deletions(-)

diff --git a/crates/solverforge/tests/list_cvrp_k_opt_time_window/domain/plan.rs b/crates/solverforge/tests/list_cvrp_k_opt_time_window/domain/plan.rs
index 4ce99c91..d794f45a 100644
--- a/crates/solverforge/tests/list_cvrp_k_opt_time_window/domain/plan.rs
+++ b/crates/solverforge/tests/list_cvrp_k_opt_time_window/domain/plan.rs
@@ -2,6 +2,7 @@ use std::sync::Arc;
 
 use solverforge::cvrp::ProblemData;
 use solverforge::prelude::*;
+use solverforge::stream::ConstraintFactory;
 
 use super::Route;
 
@@ -40,23 +41,40 @@ impl solverforge::cvrp::VrpSolution for Plan {
     }
 }
 
-fn constraints() -> impl ConstraintSet<Plan, HardSoftScore> {}
+/// Directed distance between two nodes, the depot being node 0: 1 along
+/// `0 → 1 → 2 → 3 → 4 → 0` and for `3 → 2`, 50 for `1 → 3` and `2 → 4`, 100
+/// otherwise.
+fn distance(from: usize, to: usize) -> i64 {
+    match (from, to) {
+        _ if from == to => 0,
+        (0, 1) | (1, 2) | (2, 3) | (3, 4) | (4, 0) | (3, 2) => 1,
+        (1, 3) | (2, 4) => 50,
+        _ => 100,
+    }
+}
 
-pub fn build_plan() -> Plan {
-    let mut distance_matrix = vec![vec![100_i64; 5]; 5];
-    for (idx, row) in distance_matrix.iter_mut().enumerate() {
-        row[idx] = 0;
+/// Each route's travelled distance, depot to depot.
+fn route_distance(route: &Route) -> i64 {
+    let mut previous = 0;
+    let mut total = 0;
+    for &visit in route.visits.iter().chain(std::iter::once(&0)) {
+        total += distance(previous, visit);
+        previous = visit;
     }
+    total
+}
 
-    distance_matrix[0][1] = 1;
-    distance_matrix[1][3] = 50;
-    distance_matrix[3][2] = 1;
-    distance_matrix[2][4] = 50;
-    distance_matrix[4][0] = 1;
+fn constraints() -> impl ConstraintSet<Plan, HardSoftScore> {
+    (ConstraintFactory::<Plan, HardSoftScore>::new()
+        .for_each(Plan::routes())
+        .penalize(|route: &Route| HardSoftScore::of(0, route_distance(route)))
+        .named("route distance"),)
+}
 
-    distance_matrix[1][2] = 1;
-    distance_matrix[2][3] = 1;
-    distance_matrix[3][4] = 1;
+pub fn build_plan() -> Plan {
+    let distance_matrix = (0..5)
+        .map(|from| (0..5).map(|to| distance(from, to)).collect())
+        .collect();
 
     let mut travel_times = vec![vec![0_i64; 5]; 5];
     travel_times[1][2] = 10;