WHY YOU TAKE TEN INSTEAD OF 2,3,5?

Intent here is to remove the two tests that are on the combined
selection level that should just be BnB behavior tests, that fail when
SFFO causes BnB to be skipped

src/wallet/test/coinselection_tests.cpp

@@ -91,9 +91,9 @@ static COutput MakeCoin(const CAmount& amount, bool is_eff_value = true, int nIn
     return COutput{COutPoint(tx.GetHash(), nInput), tx.vout.at(nInput), /*depth=*/ 1, /*input_bytes=*/ custom_spending_vsize, /*spendable=*/ true, /*solvable=*/ true, /*safe=*/ true, /*time=*/ 0, /*from_me=*/ false, /*fees=*/ fees};
 }
 
-static void AddCoins(std::vector<COutput>& utxo_pool, std::vector<CAmount> coins) {
+static void AddCoins(std::vector<COutput>& utxo_pool, std::vector<CAmount> coins, CFeeRate feerate = default_cs_params.m_effective_feerate) {
     for (int c : coins) {
-        utxo_pool.push_back(MakeCoin(c));
+        utxo_pool.push_back(MakeCoin(c, true, 0, feerate));
     }
 }
 
@@ -103,13 +103,13 @@ std::optional<SelectionResult> SelectCoinsBnB(std::vector<COutput>& utxo_pool, c
     return res ? std::optional<SelectionResult>(*res) : std::nullopt;
 }
 
-static void TestBnBSuccess(std::string test_title, std::vector<COutput>& utxo_pool, const CAmount& selection_target, const std::vector<CAmount>& expected_input_amounts)
+static void TestBnBSuccess(std::string test_title, std::vector<COutput>& utxo_pool, const CAmount& selection_target, const std::vector<CAmount>& expected_input_amounts, const CFeeRate& feerate = default_cs_params.m_effective_feerate )
 {
     SelectionResult expected_result(CAmount(0), SelectionAlgorithm::BNB);
     CAmount expected_amount = 0;
     for (int input_amount : expected_input_amounts) {
         OutputGroup group;
-        COutput coin = MakeCoin(input_amount);
+        COutput coin = MakeCoin(input_amount, true, 0, feerate);
         expected_amount += coin.txout.nValue;
         group.Insert(std::make_shared<COutput>(coin), /*ancestors=*/ 0, /*descendants=*/ 0);
         expected_result.AddInput(group);
@@ -138,5 +138,18 @@ BOOST_AUTO_TEST_CASE(bnb_test)
     TestBnBSuccess("Select upper bound", utxo_pool, /*selection_target=*/ 9 * CENT - default_cs_params.m_cost_of_change, /*expected_input_amounts=*/ {1 * CENT, 3 * CENT, 5 * CENT});
 }
 
+BOOST_AUTO_TEST_CASE(bnb_feerate_sensitivity_test)
+{
+    // Create sets of UTXOs with the same effective amounts at different feerates (but different absolute amounts)
+    std::vector<COutput> low_feerate_pool; // 5 sat/vB
+    AddCoins(low_feerate_pool, {2 * CENT, 3 * CENT, 5 * CENT, 10 * CENT});
+    TestBnBSuccess("Select many inputs at low feerates", low_feerate_pool, /*selection_target=*/ 10 * CENT, /*expected_input_amounts=*/ {10 * CENT});
+// TestBnBSuccess("Select many inputs at low feerates", low_feerate_pool, /*selection_target=*/ 10 * CENT, /*expected_input_amounts=*/ {2 * CENT, 3 * CENT, 5 * CENT});
+
+    std::vector<COutput> high_feerate_pool; // 25 sat/vB
+    AddCoins(high_feerate_pool, {2 * CENT, 3 * CENT, 5 * CENT, 10 * CENT}, CFeeRate{25'000});
+    TestBnBSuccess("Select one input at high feerates", high_feerate_pool, /*selection_target=*/ 10 * CENT, /*expected_input_amounts=*/ {10 * CENT}, CFeeRate{25'000});
+}
+
 BOOST_AUTO_TEST_SUITE_END()
 } // namespace wallet