Merge bitcoin/bitcoin#24584: wallet: avoid mixing different `OutputTypes` during coin selection

71d1d13627ccd27319f347e2d8167c8fe8a433f4 test: add unit test for AvailableCoins (josibake)
da03cb41a4ce15ebceee7fa4a4fdd2d3602fe284 test: functional test for new coin selection logic (josibake)
438e04845bf3302b7f459a50e88a1b772527f1e6 wallet: run coin selection by `OutputType` (josibake)
77b07072061c59f50c69be29fbcddf0d433e1077 refactor: use CoinsResult struct in SelectCoins (josibake)
2e67291ca3ab2d8f498fa910738ca655fde11c5e refactor: store by OutputType in CoinsResult (josibake)

Pull request description:

  # Concept

  Following https://github.com/bitcoin/bitcoin/pull/23789, Bitcoin Core wallet will now generate a change address that matches the payment address type. This improves privacy by not revealing which of the outputs is the change at the time of the transaction in scenarios where the input address types differ from the payment address type. However, information about the change can be leaked in a later transaction. This proposal attempts to address that concern.

  ## Leaking information in a later transaction

  Consider the following scenario:

  ![mix input types(1)](https://user-images.githubusercontent.com/7444140/158597086-788339b0-c698-4b60-bd45-9ede4cd3a483.png)

  1. Alice has a wallet with bech32 type UTXOs and pays Bob, who gives her a P2SH address
  2. Alice's wallet generates a P2SH change output, preserving her privacy in `txid: a`
  3. Alice then pays Carol, who gives her a bech32 address
  4. Alice's wallet combines the P2SH UTXO with a bech32 UTXO and `txid: b` has two bech32 outputs

  From a chain analysis perspective, it is reasonable to infer that the P2SH input in `txid: b` was the change from `txid: a`. To avoid leaking information in this scenario, Alice's wallet should avoid picking the P2SH output and instead fund the transaction with only bech32 Outputs. If the payment to Carol can be funded with just the P2SH output, it should be preferred over the bech32 outputs as this will convert the P2SH UTXO to bech32 UTXOs via the payment and change outputs of the new transaction.

  **TLDR;** Avoid mixing output types, spend non-default `OutputTypes` when it is economical to do so.

  # Approach

  `AvailableCoins` now populates a struct, which makes it easier to access coins by `OutputType`. Coin selection tries to find a funding solution by each output type and chooses the most economical by waste metric. If a solution can't be found without mixing, coin selection runs over the entire wallet, allowing mixing, which is the same as the current behavior.

  I've also added a functional test (`test/functional/wallet_avoid_mixing_output_types.py`) and unit test (`src/wallet/test/availablecoins_tests.cpp`.

ACKs for top commit:
  achow101:
    re-ACK 71d1d13627ccd27319f347e2d8167c8fe8a433f4
  aureleoules:
    ACK 71d1d13627ccd27319f347e2d8167c8fe8a433f4.
  Xekyo:
    reACK 71d1d13627ccd27319f347e2d8167c8fe8a433f4 via `git range-diff master 6530d19 71d1d13`
  LarryRuane:
    ACK 71d1d13627ccd27319f347e2d8167c8fe8a433f4

Tree-SHA512: 2e0716efdae5adf5479446fabc731ae81d595131d3b8bade98b64ba323d0e0c6d964a67f8c14c89c428998bda47993fa924f3cfca1529e2bd49eaa4e31b7e426

3 files changed, 239 insertions, 134 deletions

diff --git a/src/wallet/test/availablecoins_tests.cpp b/src/wallet/test/availablecoins_tests.cpp
new file mode 100644
index 0000000000..01d24da981
--- /dev/null
+++ b/src/wallet/test/availablecoins_tests.cpp
@@ -0,0 +1,105 @@
+// Copyright (c) 2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or https://www.opensource.org/licenses/mit-license.php.
+
+#include <validation.h>
+#include <wallet/coincontrol.h>
+#include <wallet/spend.h>
+#include <wallet/test/util.h>
+#include <wallet/test/wallet_test_fixture.h>
+
+#include <boost/test/unit_test.hpp>
+
+namespace wallet {
+BOOST_FIXTURE_TEST_SUITE(availablecoins_tests, WalletTestingSetup)
+class AvailableCoinsTestingSetup : public TestChain100Setup
+{
+public:
+    AvailableCoinsTestingSetup()
+    {
+        CreateAndProcessBlock({}, {});
+        wallet = CreateSyncedWallet(*m_node.chain, m_node.chainman->ActiveChain(), m_args, coinbaseKey);
+    }
+
+    ~AvailableCoinsTestingSetup()
+    {
+        wallet.reset();
+    }
+    CWalletTx& AddTx(CRecipient recipient)
+    {
+        CTransactionRef tx;
+        CCoinControl dummy;
+        {
+            constexpr int RANDOM_CHANGE_POSITION = -1;
+            auto res = CreateTransaction(*wallet, {recipient}, RANDOM_CHANGE_POSITION, dummy);
+            BOOST_CHECK(res);
+            tx = res.GetObj().tx;
+        }
+        wallet->CommitTransaction(tx, {}, {});
+        CMutableTransaction blocktx;
+        {
+            LOCK(wallet->cs_wallet);
+            blocktx = CMutableTransaction(*wallet->mapWallet.at(tx->GetHash()).tx);
+        }
+        CreateAndProcessBlock({CMutableTransaction(blocktx)}, GetScriptForRawPubKey(coinbaseKey.GetPubKey()));
+
+        LOCK(wallet->cs_wallet);
+        wallet->SetLastBlockProcessed(wallet->GetLastBlockHeight() + 1, m_node.chainman->ActiveChain().Tip()->GetBlockHash());
+        auto it = wallet->mapWallet.find(tx->GetHash());
+        BOOST_CHECK(it != wallet->mapWallet.end());
+        it->second.m_state = TxStateConfirmed{m_node.chainman->ActiveChain().Tip()->GetBlockHash(), m_node.chainman->ActiveChain().Height(), /*index=*/1};
+        return it->second;
+    }
+
+    std::unique_ptr<CWallet> wallet;
+};
+
+BOOST_FIXTURE_TEST_CASE(BasicOutputTypesTest, AvailableCoinsTestingSetup)
+{
+    CoinsResult available_coins;
+    BResult<CTxDestination> dest;
+    LOCK(wallet->cs_wallet);
+
+    // Verify our wallet has one usable coinbase UTXO before starting
+    // This UTXO is a P2PK, so it should show up in the Other bucket
+    available_coins = AvailableCoins(*wallet);
+    BOOST_CHECK_EQUAL(available_coins.size(), 1U);
+    BOOST_CHECK_EQUAL(available_coins.other.size(), 1U);
+
+    // We will create a self transfer for each of the OutputTypes and
+    // verify it is put in the correct bucket after running GetAvailablecoins
+    //
+    // For each OutputType, We expect 2 UTXOs in our wallet following the self transfer:
+    //   1. One UTXO as the recipient
+    //   2. One UTXO from the change, due to payment address matching logic
+
+    // Bech32m
+    dest = wallet->GetNewDestination(OutputType::BECH32M, "");
+    BOOST_ASSERT(dest.HasRes());
+    AddTx(CRecipient{{GetScriptForDestination(dest.GetObj())}, 1 * COIN, /*fSubtractFeeFromAmount=*/true});
+    available_coins = AvailableCoins(*wallet);
+    BOOST_CHECK_EQUAL(available_coins.bech32m.size(), 2U);
+
+    // Bech32
+    dest = wallet->GetNewDestination(OutputType::BECH32, "");
+    BOOST_ASSERT(dest.HasRes());
+    AddTx(CRecipient{{GetScriptForDestination(dest.GetObj())}, 2 * COIN, /*fSubtractFeeFromAmount=*/true});
+    available_coins = AvailableCoins(*wallet);
+    BOOST_CHECK_EQUAL(available_coins.bech32.size(), 2U);
+
+    // P2SH-SEGWIT
+    dest = wallet->GetNewDestination(OutputType::P2SH_SEGWIT, "");
+    AddTx(CRecipient{{GetScriptForDestination(dest.GetObj())}, 3 * COIN, /*fSubtractFeeFromAmount=*/true});
+    available_coins = AvailableCoins(*wallet);
+    BOOST_CHECK_EQUAL(available_coins.P2SH_segwit.size(), 2U);
+
+    // Legacy (P2PKH)
+    dest = wallet->GetNewDestination(OutputType::LEGACY, "");
+    BOOST_ASSERT(dest.HasRes());
+    AddTx(CRecipient{{GetScriptForDestination(dest.GetObj())}, 4 * COIN, /*fSubtractFeeFromAmount=*/true});
+    available_coins = AvailableCoins(*wallet);
+    BOOST_CHECK_EQUAL(available_coins.legacy.size(), 2U);
+}
+
+BOOST_AUTO_TEST_SUITE_END()
+} // namespace wallet
diff --git a/src/wallet/test/coinselector_tests.cpp b/src/wallet/test/coinselector_tests.cpp
index a418105ee1..cd7fd3f4dd 100644
--- a/src/wallet/test/coinselector_tests.cpp
+++ b/src/wallet/test/coinselector_tests.cpp
@@ -67,7 +67,7 @@ static void add_coin(const CAmount& nValue, int nInput, CoinSet& set, CAmount fe
     set.insert(coin);
 }
 
-static void add_coin(std::vector<COutput>& coins, CWallet& wallet, const CAmount& nValue, CFeeRate feerate = CFeeRate(0), int nAge = 6*24, bool fIsFromMe = false, int nInput=0, bool spendable = false)
+static void add_coin(CoinsResult& available_coins, CWallet& wallet, const CAmount& nValue, CFeeRate feerate = CFeeRate(0), int nAge = 6*24, bool fIsFromMe = false, int nInput =0, bool spendable = false)
 {
     CMutableTransaction tx;
     tx.nLockTime = nextLockTime++;        // so all transactions get different hashes
@@ -85,7 +85,7 @@ static void add_coin(std::vector<COutput>& coins, CWallet& wallet, const CAmount
     assert(ret.second);
     CWalletTx& wtx = (*ret.first).second;
     const auto& txout = wtx.tx->vout.at(nInput);
-    coins.emplace_back(COutPoint(wtx.GetHash(), nInput), txout, nAge, CalculateMaximumSignedInputSize(txout, &wallet, /*coin_control=*/nullptr), /*spendable=*/ true, /*solvable=*/ true, /*safe=*/ true, wtx.GetTxTime(), fIsFromMe, feerate);
+    available_coins.bech32.emplace_back(COutPoint(wtx.GetHash(), nInput), txout, nAge, CalculateMaximumSignedInputSize(txout, &wallet, /*coin_control=*/nullptr), /*spendable=*/ true, /*solvable=*/ true, /*safe=*/ true, wtx.GetTxTime(), fIsFromMe, feerate);
 }
 
 /** Check if SelectionResult a is equivalent to SelectionResult b.
@@ -129,18 +129,18 @@ static CAmount make_hard_case(int utxos, std::vector<COutput>& utxo_pool)
     return target;
 }
 
-inline std::vector<OutputGroup>& GroupCoins(const std::vector<COutput>& coins)
+inline std::vector<OutputGroup>& GroupCoins(const std::vector<COutput>& available_coins)
 {
     static std::vector<OutputGroup> static_groups;
     static_groups.clear();
-    for (auto& coin : coins) {
+    for (auto& coin : available_coins) {
         static_groups.emplace_back();
         static_groups.back().Insert(coin, /*ancestors=*/ 0, /*descendants=*/ 0, /*positive_only=*/ false);
     }
     return static_groups;
 }
 
-inline std::vector<OutputGroup>& KnapsackGroupOutputs(const std::vector<COutput>& coins, CWallet& wallet, const CoinEligibilityFilter& filter)
+inline std::vector<OutputGroup>& KnapsackGroupOutputs(const std::vector<COutput>& available_coins, CWallet& wallet, const CoinEligibilityFilter& filter)
 {
     FastRandomContext rand{};
     CoinSelectionParams coin_selection_params{
@@ -155,7 +155,7 @@ inline std::vector<OutputGroup>& KnapsackGroupOutputs(const std::vector<COutput>
         /*avoid_partial=*/ false,
     };
     static std::vector<OutputGroup> static_groups;
-    static_groups = GroupOutputs(wallet, coins, coin_selection_params, filter, /*positive_only=*/false);
+    static_groups = GroupOutputs(wallet, available_coins, coin_selection_params, filter, /*positive_only=*/false);
     return static_groups;
 }
 
@@ -307,18 +307,18 @@ BOOST_AUTO_TEST_CASE(bnb_search_test)
         wallet->SetWalletFlag(WALLET_FLAG_DESCRIPTORS);
         wallet->SetupDescriptorScriptPubKeyMans();
 
-        std::vector<COutput> coins;
+        CoinsResult available_coins;
 
-        add_coin(coins, *wallet, 1, coin_selection_params_bnb.m_effective_feerate);
-        coins.at(0).input_bytes = 40; // Make sure that it has a negative effective value. The next check should assert if this somehow got through. Otherwise it will fail
-        BOOST_CHECK(!SelectCoinsBnB(GroupCoins(coins), 1 * CENT, coin_selection_params_bnb.m_cost_of_change));
+        add_coin(available_coins, *wallet, 1, coin_selection_params_bnb.m_effective_feerate);
+        available_coins.all().at(0).input_bytes = 40; // Make sure that it has a negative effective value. The next check should assert if this somehow got through. Otherwise it will fail
+        BOOST_CHECK(!SelectCoinsBnB(GroupCoins(available_coins.all()), 1 * CENT, coin_selection_params_bnb.m_cost_of_change));
 
         // Test fees subtracted from output:
-        coins.clear();
-        add_coin(coins, *wallet, 1 * CENT, coin_selection_params_bnb.m_effective_feerate);
-        coins.at(0).input_bytes = 40;
+        available_coins.clear();
+        add_coin(available_coins, *wallet, 1 * CENT, coin_selection_params_bnb.m_effective_feerate);
+        available_coins.all().at(0).input_bytes = 40;
         coin_selection_params_bnb.m_subtract_fee_outputs = true;
-        const auto result9 = SelectCoinsBnB(GroupCoins(coins), 1 * CENT, coin_selection_params_bnb.m_cost_of_change);
+        const auto result9 = SelectCoinsBnB(GroupCoins(available_coins.all()), 1 * CENT, coin_selection_params_bnb.m_cost_of_change);
         BOOST_CHECK(result9);
         BOOST_CHECK_EQUAL(result9->GetSelectedValue(), 1 * CENT);
     }
@@ -330,16 +330,16 @@ BOOST_AUTO_TEST_CASE(bnb_search_test)
         wallet->SetWalletFlag(WALLET_FLAG_DESCRIPTORS);
         wallet->SetupDescriptorScriptPubKeyMans();
 
-        std::vector<COutput> coins;
+        CoinsResult available_coins;
 
-        add_coin(coins, *wallet, 5 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
-        add_coin(coins, *wallet, 3 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
-        add_coin(coins, *wallet, 2 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
+        add_coin(available_coins, *wallet, 5 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
+        add_coin(available_coins, *wallet, 3 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
+        add_coin(available_coins, *wallet, 2 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
         CCoinControl coin_control;
         coin_control.m_allow_other_inputs = true;
-        coin_control.Select(coins.at(0).outpoint);
+        coin_control.Select(available_coins.all().at(0).outpoint);
         coin_selection_params_bnb.m_effective_feerate = CFeeRate(0);
-        const auto result10 = SelectCoins(*wallet, coins, 10 * CENT, coin_control, coin_selection_params_bnb);
+        const auto result10 = SelectCoins(*wallet, available_coins, 10 * CENT, coin_control, coin_selection_params_bnb);
         BOOST_CHECK(result10);
     }
     {
@@ -349,52 +349,52 @@ BOOST_AUTO_TEST_CASE(bnb_search_test)
         wallet->SetWalletFlag(WALLET_FLAG_DESCRIPTORS);
         wallet->SetupDescriptorScriptPubKeyMans();
 
-        std::vector<COutput> coins;
+        CoinsResult available_coins;
 
         // single coin should be selected when effective fee > long term fee
         coin_selection_params_bnb.m_effective_feerate = CFeeRate(5000);
         coin_selection_params_bnb.m_long_term_feerate = CFeeRate(3000);
 
-        add_coin(coins, *wallet, 10 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
-        add_coin(coins, *wallet, 9 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
-        add_coin(coins, *wallet, 1 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
+        add_coin(available_coins, *wallet, 10 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
+        add_coin(available_coins, *wallet, 9 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
+        add_coin(available_coins, *wallet, 1 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
 
         expected_result.Clear();
         add_coin(10 * CENT, 2, expected_result);
         CCoinControl coin_control;
-        const auto result11 = SelectCoins(*wallet, coins, 10 * CENT, coin_control, coin_selection_params_bnb);
+        const auto result11 = SelectCoins(*wallet, available_coins, 10 * CENT, coin_control, coin_selection_params_bnb);
         BOOST_CHECK(EquivalentResult(expected_result, *result11));
-        coins.clear();
+        available_coins.clear();
 
         // more coins should be selected when effective fee < long term fee
         coin_selection_params_bnb.m_effective_feerate = CFeeRate(3000);
         coin_selection_params_bnb.m_long_term_feerate = CFeeRate(5000);
 
-        add_coin(coins, *wallet, 10 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
-        add_coin(coins, *wallet, 9 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
-        add_coin(coins, *wallet, 1 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
+        add_coin(available_coins, *wallet, 10 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
+        add_coin(available_coins, *wallet, 9 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
+        add_coin(available_coins, *wallet, 1 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
 
         expected_result.Clear();
         add_coin(9 * CENT, 2, expected_result);
         add_coin(1 * CENT, 2, expected_result);
-        const auto result12 = SelectCoins(*wallet, coins, 10 * CENT, coin_control, coin_selection_params_bnb);
+        const auto result12 = SelectCoins(*wallet, available_coins, 10 * CENT, coin_control, coin_selection_params_bnb);
         BOOST_CHECK(EquivalentResult(expected_result, *result12));
-        coins.clear();
+        available_coins.clear();
 
         // pre selected coin should be selected even if disadvantageous
         coin_selection_params_bnb.m_effective_feerate = CFeeRate(5000);
         coin_selection_params_bnb.m_long_term_feerate = CFeeRate(3000);
 
-        add_coin(coins, *wallet, 10 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
-        add_coin(coins, *wallet, 9 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
-        add_coin(coins, *wallet, 1 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
+        add_coin(available_coins, *wallet, 10 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
+        add_coin(available_coins, *wallet, 9 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
+        add_coin(available_coins, *wallet, 1 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
 
         expected_result.Clear();
         add_coin(9 * CENT, 2, expected_result);
         add_coin(1 * CENT, 2, expected_result);
         coin_control.m_allow_other_inputs = true;
-        coin_control.Select(coins.at(1).outpoint); // pre select 9 coin
-        const auto result13 = SelectCoins(*wallet, coins, 10 * CENT, coin_control, coin_selection_params_bnb);
+        coin_control.Select(available_coins.all().at(1).outpoint); // pre select 9 coin
+        const auto result13 = SelectCoins(*wallet, available_coins, 10 * CENT, coin_control, coin_selection_params_bnb);
         BOOST_CHECK(EquivalentResult(expected_result, *result13));
     }
 }
@@ -410,175 +410,175 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
     wallet->SetWalletFlag(WALLET_FLAG_DESCRIPTORS);
     wallet->SetupDescriptorScriptPubKeyMans();
 
-    std::vector<COutput> coins;
+    CoinsResult available_coins;
 
     // test multiple times to allow for differences in the shuffle order
     for (int i = 0; i < RUN_TESTS; i++)
     {
-        coins.clear();
+        available_coins.clear();
 
         // with an empty wallet we can't even pay one cent
-        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_standard), 1 * CENT, CENT));
+        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_standard), 1 * CENT, CENT));
 
-        add_coin(coins, *wallet, 1*CENT, CFeeRate(0), 4);        // add a new 1 cent coin
+        add_coin(available_coins, *wallet, 1*CENT, CFeeRate(0), 4);        // add a new 1 cent coin
 
         // with a new 1 cent coin, we still can't find a mature 1 cent
-        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_standard), 1 * CENT, CENT));
+        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_standard), 1 * CENT, CENT));
 
         // but we can find a new 1 cent
-        const auto result1 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 1 * CENT, CENT);
+        const auto result1 = KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_confirmed), 1 * CENT, CENT);
         BOOST_CHECK(result1);
         BOOST_CHECK_EQUAL(result1->GetSelectedValue(), 1 * CENT);
 
-        add_coin(coins, *wallet, 2*CENT);           // add a mature 2 cent coin
+        add_coin(available_coins, *wallet, 2*CENT);           // add a mature 2 cent coin
 
         // we can't make 3 cents of mature coins
-        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_standard), 3 * CENT, CENT));
+        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_standard), 3 * CENT, CENT));
 
         // we can make 3 cents of new coins
-        const auto result2 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 3 * CENT, CENT);
+        const auto result2 = KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_confirmed), 3 * CENT, CENT);
         BOOST_CHECK(result2);
         BOOST_CHECK_EQUAL(result2->GetSelectedValue(), 3 * CENT);
 
-        add_coin(coins, *wallet, 5*CENT);           // add a mature 5 cent coin,
-        add_coin(coins, *wallet, 10*CENT, CFeeRate(0), 3, true); // a new 10 cent coin sent from one of our own addresses
-        add_coin(coins, *wallet, 20*CENT);          // and a mature 20 cent coin
+        add_coin(available_coins, *wallet, 5*CENT);           // add a mature 5 cent coin,
+        add_coin(available_coins, *wallet, 10*CENT, CFeeRate(0), 3, true); // a new 10 cent coin sent from one of our own addresses
+        add_coin(available_coins, *wallet, 20*CENT);          // and a mature 20 cent coin
 
         // now we have new: 1+10=11 (of which 10 was self-sent), and mature: 2+5+20=27.  total = 38
 
         // we can't make 38 cents only if we disallow new coins:
-        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_standard), 38 * CENT, CENT));
+        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_standard), 38 * CENT, CENT));
         // we can't even make 37 cents if we don't allow new coins even if they're from us
-        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_standard_extra), 38 * CENT, CENT));
+        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_standard_extra), 38 * CENT, CENT));
         // but we can make 37 cents if we accept new coins from ourself
-        const auto result3 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_standard), 37 * CENT, CENT);
+        const auto result3 = KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_standard), 37 * CENT, CENT);
         BOOST_CHECK(result3);
         BOOST_CHECK_EQUAL(result3->GetSelectedValue(), 37 * CENT);
         // and we can make 38 cents if we accept all new coins
-        const auto result4 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 38 * CENT, CENT);
+        const auto result4 = KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_confirmed), 38 * CENT, CENT);
         BOOST_CHECK(result4);
         BOOST_CHECK_EQUAL(result4->GetSelectedValue(), 38 * CENT);
 
         // try making 34 cents from 1,2,5,10,20 - we can't do it exactly
-        const auto result5 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 34 * CENT, CENT);
+        const auto result5 = KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_confirmed), 34 * CENT, CENT);
         BOOST_CHECK(result5);
         BOOST_CHECK_EQUAL(result5->GetSelectedValue(), 35 * CENT);       // but 35 cents is closest
         BOOST_CHECK_EQUAL(result5->GetInputSet().size(), 3U);     // the best should be 20+10+5.  it's incredibly unlikely the 1 or 2 got included (but possible)
 
         // when we try making 7 cents, the smaller coins (1,2,5) are enough.  We should see just 2+5
-        const auto result6 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 7 * CENT, CENT);
+        const auto result6 = KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_confirmed), 7 * CENT, CENT);
         BOOST_CHECK(result6);
         BOOST_CHECK_EQUAL(result6->GetSelectedValue(), 7 * CENT);
         BOOST_CHECK_EQUAL(result6->GetInputSet().size(), 2U);
 
         // when we try making 8 cents, the smaller coins (1,2,5) are exactly enough.
-        const auto result7 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 8 * CENT, CENT);
+        const auto result7 = KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_confirmed), 8 * CENT, CENT);
         BOOST_CHECK(result7);
         BOOST_CHECK(result7->GetSelectedValue() == 8 * CENT);
         BOOST_CHECK_EQUAL(result7->GetInputSet().size(), 3U);
 
         // when we try making 9 cents, no subset of smaller coins is enough, and we get the next bigger coin (10)
-        const auto result8 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 9 * CENT, CENT);
+        const auto result8 = KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_confirmed), 9 * CENT, CENT);
         BOOST_CHECK(result8);
         BOOST_CHECK_EQUAL(result8->GetSelectedValue(), 10 * CENT);
         BOOST_CHECK_EQUAL(result8->GetInputSet().size(), 1U);
 
         // now clear out the wallet and start again to test choosing between subsets of smaller coins and the next biggest coin
-        coins.clear();
+        available_coins.clear();
 
-        add_coin(coins, *wallet,  6*CENT);
-        add_coin(coins, *wallet,  7*CENT);
-        add_coin(coins, *wallet,  8*CENT);
-        add_coin(coins, *wallet, 20*CENT);
-        add_coin(coins, *wallet, 30*CENT); // now we have 6+7+8+20+30 = 71 cents total
+        add_coin(available_coins, *wallet,  6*CENT);
+        add_coin(available_coins, *wallet,  7*CENT);
+        add_coin(available_coins, *wallet,  8*CENT);
+        add_coin(available_coins, *wallet, 20*CENT);
+        add_coin(available_coins, *wallet, 30*CENT); // now we have 6+7+8+20+30 = 71 cents total
 
         // check that we have 71 and not 72
-        const auto result9 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 71 * CENT, CENT);
+        const auto result9 = KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_confirmed), 71 * CENT, CENT);
         BOOST_CHECK(result9);
-        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 72 * CENT, CENT));
+        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_confirmed), 72 * CENT, CENT));
 
         // now try making 16 cents.  the best smaller coins can do is 6+7+8 = 21; not as good at the next biggest coin, 20
-        const auto result10 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 16 * CENT, CENT);
+        const auto result10 = KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_confirmed), 16 * CENT, CENT);
         BOOST_CHECK(result10);
         BOOST_CHECK_EQUAL(result10->GetSelectedValue(), 20 * CENT); // we should get 20 in one coin
         BOOST_CHECK_EQUAL(result10->GetInputSet().size(), 1U);
 
-        add_coin(coins, *wallet,  5*CENT); // now we have 5+6+7+8+20+30 = 75 cents total
+        add_coin(available_coins, *wallet,  5*CENT); // now we have 5+6+7+8+20+30 = 75 cents total
 
         // now if we try making 16 cents again, the smaller coins can make 5+6+7 = 18 cents, better than the next biggest coin, 20
-        const auto result11 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 16 * CENT, CENT);
+        const auto result11 = KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_confirmed), 16 * CENT, CENT);
         BOOST_CHECK(result11);
         BOOST_CHECK_EQUAL(result11->GetSelectedValue(), 18 * CENT); // we should get 18 in 3 coins
         BOOST_CHECK_EQUAL(result11->GetInputSet().size(), 3U);
 
-        add_coin(coins, *wallet,  18*CENT); // now we have 5+6+7+8+18+20+30
+        add_coin(available_coins, *wallet,  18*CENT); // now we have 5+6+7+8+18+20+30
 
         // and now if we try making 16 cents again, the smaller coins can make 5+6+7 = 18 cents, the same as the next biggest coin, 18
-        const auto result12 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 16 * CENT, CENT);
+        const auto result12 = KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_confirmed), 16 * CENT, CENT);
         BOOST_CHECK(result12);
         BOOST_CHECK_EQUAL(result12->GetSelectedValue(), 18 * CENT);  // we should get 18 in 1 coin
         BOOST_CHECK_EQUAL(result12->GetInputSet().size(), 1U); // because in the event of a tie, the biggest coin wins
 
         // now try making 11 cents.  we should get 5+6
-        const auto result13 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 11 * CENT, CENT);
+        const auto result13 = KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_confirmed), 11 * CENT, CENT);
         BOOST_CHECK(result13);
         BOOST_CHECK_EQUAL(result13->GetSelectedValue(), 11 * CENT);
         BOOST_CHECK_EQUAL(result13->GetInputSet().size(), 2U);
 
         // check that the smallest bigger coin is used
-        add_coin(coins, *wallet,  1*COIN);
-        add_coin(coins, *wallet,  2*COIN);
-        add_coin(coins, *wallet,  3*COIN);
-        add_coin(coins, *wallet,  4*COIN); // now we have 5+6+7+8+18+20+30+100+200+300+400 = 1094 cents
-        const auto result14 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 95 * CENT, CENT);
+        add_coin(available_coins, *wallet,  1*COIN);
+        add_coin(available_coins, *wallet,  2*COIN);
+        add_coin(available_coins, *wallet,  3*COIN);
+        add_coin(available_coins, *wallet,  4*COIN); // now we have 5+6+7+8+18+20+30+100+200+300+400 = 1094 cents
+        const auto result14 = KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_confirmed), 95 * CENT, CENT);
         BOOST_CHECK(result14);
         BOOST_CHECK_EQUAL(result14->GetSelectedValue(), 1 * COIN);  // we should get 1 BTC in 1 coin
         BOOST_CHECK_EQUAL(result14->GetInputSet().size(), 1U);
 
-        const auto result15 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 195 * CENT, CENT);
+        const auto result15 = KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_confirmed), 195 * CENT, CENT);
         BOOST_CHECK(result15);
         BOOST_CHECK_EQUAL(result15->GetSelectedValue(), 2 * COIN);  // we should get 2 BTC in 1 coin
         BOOST_CHECK_EQUAL(result15->GetInputSet().size(), 1U);
 
         // empty the wallet and start again, now with fractions of a cent, to test small change avoidance
 
-        coins.clear();
-        add_coin(coins, *wallet, CENT * 1 / 10);
-        add_coin(coins, *wallet, CENT * 2 / 10);
-        add_coin(coins, *wallet, CENT * 3 / 10);
-        add_coin(coins, *wallet, CENT * 4 / 10);
-        add_coin(coins, *wallet, CENT * 5 / 10);
+        available_coins.clear();
+        add_coin(available_coins, *wallet, CENT * 1 / 10);
+        add_coin(available_coins, *wallet, CENT * 2 / 10);
+        add_coin(available_coins, *wallet, CENT * 3 / 10);
+        add_coin(available_coins, *wallet, CENT * 4 / 10);
+        add_coin(available_coins, *wallet, CENT * 5 / 10);
 
         // try making 1 * CENT from the 1.5 * CENT
         // we'll get change smaller than CENT whatever happens, so can expect CENT exactly
-        const auto result16 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), CENT, CENT);
+        const auto result16 = KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_confirmed), CENT, CENT);
         BOOST_CHECK(result16);
         BOOST_CHECK_EQUAL(result16->GetSelectedValue(), CENT);
 
         // but if we add a bigger coin, small change is avoided
-        add_coin(coins, *wallet, 1111*CENT);
+        add_coin(available_coins, *wallet, 1111*CENT);
 
         // try making 1 from 0.1 + 0.2 + 0.3 + 0.4 + 0.5 + 1111 = 1112.5
-        const auto result17 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 1 * CENT, CENT);
+        const auto result17 = KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_confirmed), 1 * CENT, CENT);
         BOOST_CHECK(result17);
         BOOST_CHECK_EQUAL(result17->GetSelectedValue(), 1 * CENT); // we should get the exact amount
 
         // if we add more small coins:
-        add_coin(coins, *wallet, CENT * 6 / 10);
-        add_coin(coins, *wallet, CENT * 7 / 10);
+        add_coin(available_coins, *wallet, CENT * 6 / 10);
+        add_coin(available_coins, *wallet, CENT * 7 / 10);
 
         // and try again to make 1.0 * CENT
-        const auto result18 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 1 * CENT, CENT);
+        const auto result18 = KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_confirmed), 1 * CENT, CENT);
         BOOST_CHECK(result18);
         BOOST_CHECK_EQUAL(result18->GetSelectedValue(), 1 * CENT); // we should get the exact amount
 
         // run the 'mtgox' test (see https://blockexplorer.com/tx/29a3efd3ef04f9153d47a990bd7b048a4b2d213daaa5fb8ed670fb85f13bdbcf)
         // they tried to consolidate 10 50k coins into one 500k coin, and ended up with 50k in change
-        coins.clear();
+        available_coins.clear();
         for (int j = 0; j < 20; j++)
-            add_coin(coins, *wallet, 50000 * COIN);
+            add_coin(available_coins, *wallet, 50000 * COIN);
 
-        const auto result19 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 500000 * COIN, CENT);
+        const auto result19 = KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_confirmed), 500000 * COIN, CENT);
         BOOST_CHECK(result19);
         BOOST_CHECK_EQUAL(result19->GetSelectedValue(), 500000 * COIN); // we should get the exact amount
         BOOST_CHECK_EQUAL(result19->GetInputSet().size(), 10U); // in ten coins
@@ -587,41 +587,41 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
         // we need to try finding an exact subset anyway
 
         // sometimes it will fail, and so we use the next biggest coin:
-        coins.clear();
-        add_coin(coins, *wallet, CENT * 5 / 10);
-        add_coin(coins, *wallet, CENT * 6 / 10);
-        add_coin(coins, *wallet, CENT * 7 / 10);
-        add_coin(coins, *wallet, 1111 * CENT);
-        const auto result20 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 1 * CENT, CENT);
+        available_coins.clear();
+        add_coin(available_coins, *wallet, CENT * 5 / 10);
+        add_coin(available_coins, *wallet, CENT * 6 / 10);
+        add_coin(available_coins, *wallet, CENT * 7 / 10);
+        add_coin(available_coins, *wallet, 1111 * CENT);
+        const auto result20 = KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_confirmed), 1 * CENT, CENT);
         BOOST_CHECK(result20);
         BOOST_CHECK_EQUAL(result20->GetSelectedValue(), 1111 * CENT); // we get the bigger coin
         BOOST_CHECK_EQUAL(result20->GetInputSet().size(), 1U);
 
         // but sometimes it's possible, and we use an exact subset (0.4 + 0.6 = 1.0)
-        coins.clear();
-        add_coin(coins, *wallet, CENT * 4 / 10);
-        add_coin(coins, *wallet, CENT * 6 / 10);
-        add_coin(coins, *wallet, CENT * 8 / 10);
-        add_coin(coins, *wallet, 1111 * CENT);
-        const auto result21 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), CENT, CENT);
+        available_coins.clear();
+        add_coin(available_coins, *wallet, CENT * 4 / 10);
+        add_coin(available_coins, *wallet, CENT * 6 / 10);
+        add_coin(available_coins, *wallet, CENT * 8 / 10);
+        add_coin(available_coins, *wallet, 1111 * CENT);
+        const auto result21 = KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_confirmed), CENT, CENT);
         BOOST_CHECK(result21);
         BOOST_CHECK_EQUAL(result21->GetSelectedValue(), CENT);   // we should get the exact amount
         BOOST_CHECK_EQUAL(result21->GetInputSet().size(), 2U); // in two coins 0.4+0.6
 
         // test avoiding small change
-        coins.clear();
-        add_coin(coins, *wallet, CENT * 5 / 100);
-        add_coin(coins, *wallet, CENT * 1);
-        add_coin(coins, *wallet, CENT * 100);
+        available_coins.clear();
+        add_coin(available_coins, *wallet, CENT * 5 / 100);
+        add_coin(available_coins, *wallet, CENT * 1);
+        add_coin(available_coins, *wallet, CENT * 100);
 
         // trying to make 100.01 from these three coins
-        const auto result22 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), CENT * 10001 / 100, CENT);
+        const auto result22 = KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_confirmed), CENT * 10001 / 100, CENT);
         BOOST_CHECK(result22);
         BOOST_CHECK_EQUAL(result22->GetSelectedValue(), CENT * 10105 / 100); // we should get all coins
         BOOST_CHECK_EQUAL(result22->GetInputSet().size(), 3U);
 
         // but if we try to make 99.9, we should take the bigger of the two small coins to avoid small change
-        const auto result23 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), CENT * 9990 / 100, CENT);
+        const auto result23 = KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_confirmed), CENT * 9990 / 100, CENT);
         BOOST_CHECK(result23);
         BOOST_CHECK_EQUAL(result23->GetSelectedValue(), 101 * CENT);
         BOOST_CHECK_EQUAL(result23->GetInputSet().size(), 2U);
@@ -629,14 +629,14 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
 
     // test with many inputs
     for (CAmount amt=1500; amt < COIN; amt*=10) {
-        coins.clear();
+        available_coins.clear();
         // Create 676 inputs (=  (old MAX_STANDARD_TX_SIZE == 100000)  / 148 bytes per input)
         for (uint16_t j = 0; j < 676; j++)
-            add_coin(coins, *wallet, amt);
+            add_coin(available_coins, *wallet, amt);
 
         // We only create the wallet once to save time, but we still run the coin selection RUN_TESTS times.
         for (int i = 0; i < RUN_TESTS; i++) {
-            const auto result24 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 2000, CENT);
+            const auto result24 = KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_confirmed), 2000, CENT);
             BOOST_CHECK(result24);
 
             if (amt - 2000 < CENT) {
@@ -655,17 +655,17 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
 
     // test randomness
     {
-        coins.clear();
+        available_coins.clear();
         for (int i2 = 0; i2 < 100; i2++)
-            add_coin(coins, *wallet, COIN);
+            add_coin(available_coins, *wallet, COIN);
 
         // Again, we only create the wallet once to save time, but we still run the coin selection RUN_TESTS times.
         for (int i = 0; i < RUN_TESTS; i++) {
             // picking 50 from 100 coins doesn't depend on the shuffle,
             // but does depend on randomness in the stochastic approximation code
-            const auto result25 = KnapsackSolver(GroupCoins(coins), 50 * COIN, CENT);
+            const auto result25 = KnapsackSolver(GroupCoins(available_coins.all()), 50 * COIN, CENT);
             BOOST_CHECK(result25);
-            const auto result26 = KnapsackSolver(GroupCoins(coins), 50 * COIN, CENT);
+            const auto result26 = KnapsackSolver(GroupCoins(available_coins.all()), 50 * COIN, CENT);
             BOOST_CHECK(result26);
             BOOST_CHECK(!EqualResult(*result25, *result26));
 
@@ -676,9 +676,9 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
                 // When choosing 1 from 100 identical coins, 1% of the time, this test will choose the same coin twice
                 // which will cause it to fail.
                 // To avoid that issue, run the test RANDOM_REPEATS times and only complain if all of them fail
-                const auto result27 = KnapsackSolver(GroupCoins(coins), COIN, CENT);
+                const auto result27 = KnapsackSolver(GroupCoins(available_coins.all()), COIN, CENT);
                 BOOST_CHECK(result27);
-                const auto result28 = KnapsackSolver(GroupCoins(coins), COIN, CENT);
+                const auto result28 = KnapsackSolver(GroupCoins(available_coins.all()), COIN, CENT);
                 BOOST_CHECK(result28);
                 if (EqualResult(*result27, *result28))
                     fails++;
@@ -689,19 +689,19 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
         // add 75 cents in small change.  not enough to make 90 cents,
         // then try making 90 cents.  there are multiple competing "smallest bigger" coins,
         // one of which should be picked at random
-        add_coin(coins, *wallet, 5 * CENT);
-        add_coin(coins, *wallet, 10 * CENT);
-        add_coin(coins, *wallet, 15 * CENT);
-        add_coin(coins, *wallet, 20 * CENT);
-        add_coin(coins, *wallet, 25 * CENT);
+        add_coin(available_coins, *wallet, 5 * CENT);
+        add_coin(available_coins, *wallet, 10 * CENT);
+        add_coin(available_coins, *wallet, 15 * CENT);
+        add_coin(available_coins, *wallet, 20 * CENT);
+        add_coin(available_coins, *wallet, 25 * CENT);
 
         for (int i = 0; i < RUN_TESTS; i++) {
             int fails = 0;
             for (int j = 0; j < RANDOM_REPEATS; j++)
             {
-                const auto result29 = KnapsackSolver(GroupCoins(coins), 90 * CENT, CENT);
+                const auto result29 = KnapsackSolver(GroupCoins(available_coins.all()), 90 * CENT, CENT);
                 BOOST_CHECK(result29);
-                const auto result30 = KnapsackSolver(GroupCoins(coins), 90 * CENT, CENT);
+                const auto result30 = KnapsackSolver(GroupCoins(available_coins.all()), 90 * CENT, CENT);
                 BOOST_CHECK(result30);
                 if (EqualResult(*result29, *result30))
                     fails++;
@@ -720,14 +720,14 @@ BOOST_AUTO_TEST_CASE(ApproximateBestSubset)
     wallet->SetWalletFlag(WALLET_FLAG_DESCRIPTORS);
     wallet->SetupDescriptorScriptPubKeyMans();
 
-    std::vector<COutput> coins;
+    CoinsResult available_coins;
 
     // Test vValue sort order
     for (int i = 0; i < 1000; i++)
-        add_coin(coins, *wallet, 1000 * COIN);
-    add_coin(coins, *wallet, 3 * COIN);
+        add_coin(available_coins, *wallet, 1000 * COIN);
+    add_coin(available_coins, *wallet, 3 * COIN);
 
-    const auto result = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_standard), 1003 * COIN, CENT, rand);
+    const auto result = KnapsackSolver(KnapsackGroupOutputs(available_coins.all(), *wallet, filter_standard), 1003 * COIN, CENT, rand);
     BOOST_CHECK(result);
     BOOST_CHECK_EQUAL(result->GetSelectedValue(), 1003 * COIN);
     BOOST_CHECK_EQUAL(result->GetInputSet().size(), 2U);
@@ -750,14 +750,14 @@ BOOST_AUTO_TEST_CASE(SelectCoins_test)
     // Run this test 100 times
     for (int i = 0; i < 100; ++i)
     {
-        std::vector<COutput> coins;
+        CoinsResult available_coins;
         CAmount balance{0};
 
         // Make a wallet with 1000 exponentially distributed random inputs
         for (int j = 0; j < 1000; ++j)
         {
             CAmount val = distribution(generator)*10000000;
-            add_coin(coins, *wallet, val);
+            add_coin(available_coins, *wallet, val);
             balance += val;
         }
 
@@ -780,7 +780,7 @@ BOOST_AUTO_TEST_CASE(SelectCoins_test)
             /*avoid_partial=*/ false,
         };
         CCoinControl cc;
-        const auto result = SelectCoins(*wallet, coins, target, cc, cs_params);
+        const auto result = SelectCoins(*wallet, available_coins, target, cc, cs_params);
         BOOST_CHECK(result);
         BOOST_CHECK_GE(result->GetSelectedValue(), target);
     }
diff --git a/src/wallet/test/wallet_tests.cpp b/src/wallet/test/wallet_tests.cpp
index 7377a36f5e..81183aa738 100644
--- a/src/wallet/test/wallet_tests.cpp
+++ b/src/wallet/test/wallet_tests.cpp
@@ -591,7 +591,7 @@ BOOST_FIXTURE_TEST_CASE(ListCoinsTest, ListCoinsTestingSetup)
     // Lock both coins. Confirm number of available coins drops to 0.
     {
         LOCK(wallet->cs_wallet);
-        BOOST_CHECK_EQUAL(AvailableCoinsListUnspent(*wallet).coins.size(), 2U);
+        BOOST_CHECK_EQUAL(AvailableCoinsListUnspent(*wallet).size(), 2U);
     }
     for (const auto& group : list) {
         for (const auto& coin : group.second) {
@@ -601,7 +601,7 @@ BOOST_FIXTURE_TEST_CASE(ListCoinsTest, ListCoinsTestingSetup)
     }
     {
         LOCK(wallet->cs_wallet);
-        BOOST_CHECK_EQUAL(AvailableCoinsListUnspent(*wallet).coins.size(), 0U);
+        BOOST_CHECK_EQUAL(AvailableCoinsListUnspent(*wallet).size(), 0U);
     }
     // Confirm ListCoins still returns same result as before, despite coins
     // being locked.