test: pin max2sat maxcut affine relation

Author: GiggleLiu

src/unit_tests/rules/maximum2satisfiability_maxcut.rs

@@ -52,6 +52,26 @@ fn test_maximum2satisfiability_to_maxcut_structure() {
     assert_eq!(target.evaluate(&target_solution), Max(Some(2)));
 }
 
+#[test]
+fn test_maximum2satisfiability_to_maxcut_issue_affine_relation_on_all_partitions() {
+    let source = make_issue_instance();
+    let reduction = ReduceTo::<MaxCut<SimpleGraph, i32>>::reduce_to(&source);
+    let target = reduction.target_problem();
+
+    // For this issue instance, every partition satisfies
+    // 2 * satisfied_clauses = 8 + cut_weight.
+    for mask in 0..(1usize << target.num_vertices()) {
+        let target_solution: Vec<usize> = (0..target.num_vertices())
+            .map(|bit| (mask >> bit) & 1)
+            .collect();
+        let source_solution = reduction.extract_solution(&target_solution);
+        let satisfied = source.evaluate(&source_solution).unwrap() as i32;
+        let cut_weight = target.evaluate(&target_solution).unwrap();
+
+        assert_eq!(2 * satisfied, 8 + cut_weight, "target config {target_solution:?}");
+    }
+}
+
 #[test]
 fn test_maximum2satisfiability_to_maxcut_extract_solution_uses_reference_vertex() {
     let source = make_issue_instance();