DEBUG unit test availablecoins_tests fails intermittently

this is a debugging commit the previously introduced
availablecoins_tests in the merge of bitcoin/bitcoin#24584

about 30% of the time the test fails with "invalid schnorr signature"
when trying to verify the signature of the transaction it has just
created

this only occurs when both bech32 and bech32m tests are run in the test.
removing either one does not show the issue. even stranger, the issue
only occurs when bech32m is run before bech32 as it is in the upstream
PR. swapping these around so that bech32 is run before bech32m works
around the issue - BUT WHY

src/script/interpreter.cpp

@@ -445,6 +445,14 @@ static bool EvalChecksigPreTapscript(const valtype& vchSig, const valtype& vchPu
     return true;
 }
 
+static void print_hex(const unsigned char* data, size_t size) {
+    size_t i;
+    for (i = 0; i < size; i++) {
+        printf("%02x", data[i]);
+    }
+    printf("\n");
+}
+
 static bool EvalTapScriptCheckSigFromStack(const valtype& sig, const valtype& vchPubKey, ScriptExecutionData& execdata, unsigned int flags, const valtype& msg, SigVersion sigversion, ScriptError* serror, bool& success)
 {
     // This code follows the behaviour of EvalCheckSigTapscript
@@ -2836,7 +2844,19 @@ bool GenericTransactionSignatureChecker<T>::VerifyECDSASignature(const std::vect
 template <class T>
 bool GenericTransactionSignatureChecker<T>::VerifySchnorrSignature(Span<const unsigned char> sig, const XOnlyPubKey& pubkey, const uint256& sighash) const
 {
-    return pubkey.VerifySchnorr(sighash, sig);
+    std::cout << "sig: ";
+    print_hex(sig.data(), sig.size());
+    std::cout << "pubkey: ";
+    print_hex(pubkey.data(), pubkey.size());
+    std::cout << "sighash: " << sighash.GetHex() << std::endl;;
+
+    auto r = pubkey.VerifySchnorr(sighash, sig);
+    if (r) {
+        std::cout << "verify passed\n";
+    } else {
+        std::cout << "verify failed\n";
+    }
+    return r;
 }
 
 template <class T>

src/wallet/spend.cpp

@@ -1812,7 +1812,10 @@ static BResult<CreatedTransactionResult> CreateTransactionInternal(
 
 
     if (sign) {
-        if (!wallet.SignTransaction(txNew)) {
+        auto s = wallet.SignTransaction(txNew);
+                std::cout << "signed: " << s << std::endl;
+        if (!s) {
+                std::cout << "internal return: " << __LINE__ << std::endl;
             return _("Signing transaction failed");
         }
     }
@@ -1889,7 +1892,10 @@ BResult<CreatedTransactionResult> CreateTransaction(
     auto res = CreateTransactionInternal(wallet, vecSend, change_pos, coin_control, sign, blind_details, issuance_details);
     TRACE4(coin_selection, normal_create_tx_internal, wallet.GetName().c_str(), res.HasRes(),
            res ? res.GetObj().fee : 0, res ? res.GetObj().change_pos : 0);
-    if (!res) return res;
+    if (!res) {
+        std::cout << "returning\n";
+        return res;
+    }
     const auto& txr_ungrouped = res.GetObj();
     // try with avoidpartialspends unless it's enabled already
     if (txr_ungrouped.fee > 0 /* 0 means non-functional fee rate estimation */ && wallet.m_max_aps_fee > -1 && !coin_control.m_avoid_partial_spends) {

src/wallet/test/availablecoins_tests.cpp

@@ -32,8 +32,14 @@ class AvailableCoinsTestingSetup : public TestChain100Setup
         {
             constexpr int RANDOM_CHANGE_POSITION = -1;
             auto res = CreateTransaction(*wallet, {recipient}, RANDOM_CHANGE_POSITION, dummy);
-            BOOST_CHECK(res);
-            tx = res.GetObj().tx;
+            // BOOST_CHECK(res);
+            if (res) {
+                tx = res.GetObj().tx;
+                std::cout << "pass\n";
+            } else {
+                std::cout << "fail\n";
+                BOOST_CHECK(res);
+            }
         }
         wallet->CommitTransaction(tx, {}, {});
         CMutableTransaction blocktx;
@@ -76,29 +82,33 @@ BOOST_FIXTURE_TEST_CASE(BasicOutputTypesTest, AvailableCoinsTestingSetup)
     // Bech32m
     dest = wallet->GetNewDestination(OutputType::BECH32M, "");
     BOOST_ASSERT(dest.HasRes());
-    AddTx(CRecipient{{GetScriptForDestination(dest.GetObj())}, 1 * COIN, CAsset(), CPubKey(), /*fSubtractFeeFromAmount=*/true});
+    std::cout << "bech32m\n";
+    AddTx(CRecipient{{GetScriptForDestination(dest.GetObj())}, 1 * COIN, ::policyAsset, CPubKey(), /*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, CAsset(), CPubKey(), /*fSubtractFeeFromAmount=*/true});
+    // std::cout << "bech32\n";
+    AddTx(CRecipient{{GetScriptForDestination(dest.GetObj())}, 2 * COIN, ::policyAsset, CPubKey(), /*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, CAsset(), CPubKey(), /*fSubtractFeeFromAmount=*/true});
-    available_coins = AvailableCoins(*wallet);
-    BOOST_CHECK_EQUAL(available_coins.P2SH_segwit.size(), 2U);
+    //  //P2SH-SEGWIT
+    // dest = wallet->GetNewDestination(OutputType::P2SH_SEGWIT, "");
+    // std::cout << "p2sh\n";
+    // AddTx(CRecipient{{GetScriptForDestination(dest.GetObj())}, 3 * COIN, ::policyAsset, CPubKey(), /*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, CAsset(), CPubKey(), /*fSubtractFeeFromAmount=*/true});
-    available_coins = AvailableCoins(*wallet);
-    BOOST_CHECK_EQUAL(available_coins.legacy.size(), 2U);
+    // dest = wallet->GetNewDestination(OutputType::LEGACY, "");
+    // std::cout << "legacy\n";
+    // BOOST_ASSERT(dest.HasRes());
+    // AddTx(CRecipient{{GetScriptForDestination(dest.GetObj())}, 4 * COIN, ::policyAsset, CPubKey(), /*fSubtractFeeFromAmount=*/true});
+    // available_coins = AvailableCoins(*wallet);
+    // BOOST_CHECK_EQUAL(available_coins.legacy.size(), 2U);
 }
 
 BOOST_AUTO_TEST_SUITE_END()

src/wallet/test/util.cpp

@@ -32,6 +32,7 @@ std::unique_ptr<CWallet> CreateSyncedWallet(interfaces::Chain& chain, CChain& cc
         FlatSigningProvider provider;
         std::string error;
         std::unique_ptr<Descriptor> desc = Parse("combo(" + EncodeSecret(key) + ")", provider, error, /* require_checksum=*/ false);
+        std::cout << "desc: " << desc->ToString() << std::endl;
         assert(desc);
         WalletDescriptor w_desc(std::move(desc), 0, 0, 1, 1);
         if (!wallet->AddWalletDescriptor(w_desc, provider, "", false)) assert(false);

test.sh

@@ -0,0 +1,5 @@
+#!/usr/bin/env bash
+
+# set -euxo pipefail
+
+for N in $(seq 1 100); do src/test/test_bitcoin --run_test=availablecoins_tests; done