Have SelectCoinsMinConf and SelectCoins use BnB or Knapsack and use it

Allows SelectCoinsMinConf and SelectCoins be able to switch between
using BnB or Knapsack for choosing coins.

Has SelectCoinsMinConf do the preprocessing necessary to support either
BnB or Knapsack. This includes calculating the filtering the effective
values for each input.

Uses BnB in CreateTransaction to find an exact match for the output.
If BnB fails, it will fallback to the Knapsack solver.

1 files changed, 87 insertions, 37 deletions

diff --git a/src/wallet/test/coinselector_tests.cpp b/src/wallet/test/coinselector_tests.cpp
index aa1579c20f..d295398301 100644
--- a/src/wallet/test/coinselector_tests.cpp
+++ b/src/wallet/test/coinselector_tests.cpp
@@ -28,6 +28,7 @@ typedef std::set<CInputCoin> CoinSet;
 
 static std::vector<COutput> vCoins;
 static const CWallet testWallet("dummy", CWalletDBWrapper::CreateDummy());
+static CAmount balance = 0;
 
 static void add_coin(const CAmount& nValue, int nInput, std::vector<CInputCoin>& set)
 {
@@ -47,6 +48,7 @@ static void add_coin(const CAmount& nValue, int nInput, CoinSet& set)
 
 static void add_coin(const CAmount& nValue, int nAge = 6*24, bool fIsFromMe = false, int nInput=0)
 {
+    balance += nValue;
     static int nextLockTime = 0;
     CMutableTransaction tx;
     tx.nLockTime = nextLockTime++;        // so all transactions get different hashes
@@ -72,6 +74,7 @@ static void empty_wallet(void)
 {
     vCoins.clear();
     wtxn.clear();
+    balance = 0;
 }
 
 static bool equal_sets(CoinSet a, CoinSet b)
@@ -209,11 +212,13 @@ BOOST_AUTO_TEST_CASE(bnb_search_test)
 CoinEligibilityFilter filter_standard(1, 6, 0);
 CoinEligibilityFilter filter_confirmed(1, 1, 0);
 CoinEligibilityFilter filter_standard_extra(6, 6, 0);
+CoinSelectionParams coin_selection_params(false, 0, 0, CFeeRate(0), 0);
 
 BOOST_AUTO_TEST_CASE(knapsack_solver_test)
 {
     CoinSet setCoinsRet, setCoinsRet2;
     CAmount nValueRet;
+    bool bnb_used;
 
     LOCK(testWallet.cs_wallet);
 
@@ -223,24 +228,24 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
         empty_wallet();
 
         // with an empty wallet we can't even pay one cent
-        BOOST_CHECK(!testWallet.SelectCoinsMinConf( 1 * CENT, filter_standard, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK(!testWallet.SelectCoinsMinConf( 1 * CENT, filter_standard, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
 
         add_coin(1*CENT, 4);        // add a new 1 cent coin
 
         // with a new 1 cent coin, we still can't find a mature 1 cent
-        BOOST_CHECK(!testWallet.SelectCoinsMinConf( 1 * CENT, filter_standard, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK(!testWallet.SelectCoinsMinConf( 1 * CENT, filter_standard, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
 
         // but we can find a new 1 cent
-        BOOST_CHECK( testWallet.SelectCoinsMinConf( 1 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( testWallet.SelectCoinsMinConf( 1 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
         BOOST_CHECK_EQUAL(nValueRet, 1 * CENT);
 
         add_coin(2*CENT);           // add a mature 2 cent coin
 
         // we can't make 3 cents of mature coins
-        BOOST_CHECK(!testWallet.SelectCoinsMinConf( 3 * CENT, filter_standard, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK(!testWallet.SelectCoinsMinConf( 3 * CENT, filter_standard, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
 
         // we can make 3 cents of new coins
-        BOOST_CHECK( testWallet.SelectCoinsMinConf( 3 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( testWallet.SelectCoinsMinConf( 3 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
         BOOST_CHECK_EQUAL(nValueRet, 3 * CENT);
 
         add_coin(5*CENT);           // add a mature 5 cent coin,
@@ -250,33 +255,33 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
         // 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(!testWallet.SelectCoinsMinConf(38 * CENT, filter_standard, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK(!testWallet.SelectCoinsMinConf(38 * CENT, filter_standard, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
         // we can't even make 37 cents if we don't allow new coins even if they're from us
-        BOOST_CHECK(!testWallet.SelectCoinsMinConf(38 * CENT, filter_standard_extra, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK(!testWallet.SelectCoinsMinConf(38 * CENT, filter_standard_extra, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
         // but we can make 37 cents if we accept new coins from ourself
-        BOOST_CHECK( testWallet.SelectCoinsMinConf(37 * CENT, filter_standard, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( testWallet.SelectCoinsMinConf(37 * CENT, filter_standard, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
         BOOST_CHECK_EQUAL(nValueRet, 37 * CENT);
         // and we can make 38 cents if we accept all new coins
-        BOOST_CHECK( testWallet.SelectCoinsMinConf(38 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( testWallet.SelectCoinsMinConf(38 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
         BOOST_CHECK_EQUAL(nValueRet, 38 * CENT);
 
         // try making 34 cents from 1,2,5,10,20 - we can't do it exactly
-        BOOST_CHECK( testWallet.SelectCoinsMinConf(34 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( testWallet.SelectCoinsMinConf(34 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
         BOOST_CHECK_EQUAL(nValueRet, 35 * CENT);       // but 35 cents is closest
         BOOST_CHECK_EQUAL(setCoinsRet.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
-        BOOST_CHECK( testWallet.SelectCoinsMinConf( 7 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( testWallet.SelectCoinsMinConf( 7 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
         BOOST_CHECK_EQUAL(nValueRet, 7 * CENT);
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 2U);
 
         // when we try making 8 cents, the smaller coins (1,2,5) are exactly enough.
-        BOOST_CHECK( testWallet.SelectCoinsMinConf( 8 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( testWallet.SelectCoinsMinConf( 8 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
         BOOST_CHECK(nValueRet == 8 * CENT);
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 3U);
 
         // when we try making 9 cents, no subset of smaller coins is enough, and we get the next bigger coin (10)
-        BOOST_CHECK( testWallet.SelectCoinsMinConf( 9 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( testWallet.SelectCoinsMinConf( 9 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
         BOOST_CHECK_EQUAL(nValueRet, 10 * CENT);
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 1U);
 
@@ -290,30 +295,30 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
         add_coin(30*CENT); // now we have 6+7+8+20+30 = 71 cents total
 
         // check that we have 71 and not 72
-        BOOST_CHECK( testWallet.SelectCoinsMinConf(71 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet));
-        BOOST_CHECK(!testWallet.SelectCoinsMinConf(72 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( testWallet.SelectCoinsMinConf(71 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
+        BOOST_CHECK(!testWallet.SelectCoinsMinConf(72 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
 
         // 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
-        BOOST_CHECK( testWallet.SelectCoinsMinConf(16 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( testWallet.SelectCoinsMinConf(16 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
         BOOST_CHECK_EQUAL(nValueRet, 20 * CENT); // we should get 20 in one coin
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 1U);
 
         add_coin( 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
-        BOOST_CHECK( testWallet.SelectCoinsMinConf(16 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( testWallet.SelectCoinsMinConf(16 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
         BOOST_CHECK_EQUAL(nValueRet, 18 * CENT); // we should get 18 in 3 coins
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 3U);
 
         add_coin( 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
-        BOOST_CHECK( testWallet.SelectCoinsMinConf(16 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( testWallet.SelectCoinsMinConf(16 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
         BOOST_CHECK_EQUAL(nValueRet, 18 * CENT);  // we should get 18 in 1 coin
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 1U); // because in the event of a tie, the biggest coin wins
 
         // now try making 11 cents.  we should get 5+6
-        BOOST_CHECK( testWallet.SelectCoinsMinConf(11 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( testWallet.SelectCoinsMinConf(11 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
         BOOST_CHECK_EQUAL(nValueRet, 11 * CENT);
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 2U);
 
@@ -322,11 +327,11 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
         add_coin( 2*COIN);
         add_coin( 3*COIN);
         add_coin( 4*COIN); // now we have 5+6+7+8+18+20+30+100+200+300+400 = 1094 cents
-        BOOST_CHECK( testWallet.SelectCoinsMinConf(95 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( testWallet.SelectCoinsMinConf(95 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
         BOOST_CHECK_EQUAL(nValueRet, 1 * COIN);  // we should get 1 BTC in 1 coin
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 1U);
 
-        BOOST_CHECK( testWallet.SelectCoinsMinConf(195 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( testWallet.SelectCoinsMinConf(195 * CENT, filter_confirmed, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
         BOOST_CHECK_EQUAL(nValueRet, 2 * COIN);  // we should get 2 BTC in 1 coin
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 1U);
 
@@ -341,14 +346,14 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
 
         // try making 1 * MIN_CHANGE from the 1.5 * MIN_CHANGE
         // we'll get change smaller than MIN_CHANGE whatever happens, so can expect MIN_CHANGE exactly
-        BOOST_CHECK( testWallet.SelectCoinsMinConf(MIN_CHANGE, filter_confirmed, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( testWallet.SelectCoinsMinConf(MIN_CHANGE, filter_confirmed, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
         BOOST_CHECK_EQUAL(nValueRet, MIN_CHANGE);
 
         // but if we add a bigger coin, small change is avoided
         add_coin(1111*MIN_CHANGE);
 
         // try making 1 from 0.1 + 0.2 + 0.3 + 0.4 + 0.5 + 1111 = 1112.5
-        BOOST_CHECK( testWallet.SelectCoinsMinConf(1 * MIN_CHANGE, filter_confirmed, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( testWallet.SelectCoinsMinConf(1 * MIN_CHANGE, filter_confirmed, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
         BOOST_CHECK_EQUAL(nValueRet, 1 * MIN_CHANGE); // we should get the exact amount
 
         // if we add more small coins:
@@ -356,7 +361,7 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
         add_coin(MIN_CHANGE * 7 / 10);
 
         // and try again to make 1.0 * MIN_CHANGE
-        BOOST_CHECK( testWallet.SelectCoinsMinConf(1 * MIN_CHANGE, filter_confirmed, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( testWallet.SelectCoinsMinConf(1 * MIN_CHANGE, filter_confirmed, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
         BOOST_CHECK_EQUAL(nValueRet, 1 * MIN_CHANGE); // we should get the exact amount
 
         // run the 'mtgox' test (see http://blockexplorer.com/tx/29a3efd3ef04f9153d47a990bd7b048a4b2d213daaa5fb8ed670fb85f13bdbcf)
@@ -365,7 +370,7 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
         for (int j = 0; j < 20; j++)
             add_coin(50000 * COIN);
 
-        BOOST_CHECK( testWallet.SelectCoinsMinConf(500000 * COIN, filter_confirmed, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( testWallet.SelectCoinsMinConf(500000 * COIN, filter_confirmed, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
         BOOST_CHECK_EQUAL(nValueRet, 500000 * COIN); // we should get the exact amount
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 10U); // in ten coins
 
@@ -378,7 +383,7 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
         add_coin(MIN_CHANGE * 6 / 10);
         add_coin(MIN_CHANGE * 7 / 10);
         add_coin(1111 * MIN_CHANGE);
-        BOOST_CHECK( testWallet.SelectCoinsMinConf(1 * MIN_CHANGE, filter_confirmed, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( testWallet.SelectCoinsMinConf(1 * MIN_CHANGE, filter_confirmed, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
         BOOST_CHECK_EQUAL(nValueRet, 1111 * MIN_CHANGE); // we get the bigger coin
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 1U);
 
@@ -388,7 +393,7 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
         add_coin(MIN_CHANGE * 6 / 10);
         add_coin(MIN_CHANGE * 8 / 10);
         add_coin(1111 * MIN_CHANGE);
-        BOOST_CHECK( testWallet.SelectCoinsMinConf(MIN_CHANGE, filter_confirmed, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK( testWallet.SelectCoinsMinConf(MIN_CHANGE, filter_confirmed, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
         BOOST_CHECK_EQUAL(nValueRet, MIN_CHANGE);   // we should get the exact amount
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 2U); // in two coins 0.4+0.6
 
@@ -399,12 +404,12 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
         add_coin(MIN_CHANGE * 100);
 
         // trying to make 100.01 from these three coins
-        BOOST_CHECK(testWallet.SelectCoinsMinConf(MIN_CHANGE * 10001 / 100, filter_confirmed, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK(testWallet.SelectCoinsMinConf(MIN_CHANGE * 10001 / 100, filter_confirmed, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
         BOOST_CHECK_EQUAL(nValueRet, MIN_CHANGE * 10105 / 100); // we should get all coins
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 3U);
 
         // but if we try to make 99.9, we should take the bigger of the two small coins to avoid small change
-        BOOST_CHECK(testWallet.SelectCoinsMinConf(MIN_CHANGE * 9990 / 100, filter_confirmed, vCoins, setCoinsRet, nValueRet));
+        BOOST_CHECK(testWallet.SelectCoinsMinConf(MIN_CHANGE * 9990 / 100, filter_confirmed, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
         BOOST_CHECK_EQUAL(nValueRet, 101 * MIN_CHANGE);
         BOOST_CHECK_EQUAL(setCoinsRet.size(), 2U);
 
@@ -414,7 +419,7 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
              // Create 676 inputs (=  (old MAX_STANDARD_TX_SIZE == 100000)  / 148 bytes per input)
              for (uint16_t j = 0; j < 676; j++)
                  add_coin(amt);
-             BOOST_CHECK(testWallet.SelectCoinsMinConf(2000, filter_confirmed, vCoins, setCoinsRet, nValueRet));
+             BOOST_CHECK(testWallet.SelectCoinsMinConf(2000, filter_confirmed, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
              if (amt - 2000 < MIN_CHANGE) {
                  // needs more than one input:
                  uint16_t returnSize = std::ceil((2000.0 + MIN_CHANGE)/amt);
@@ -436,8 +441,8 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
 
             // picking 50 from 100 coins doesn't depend on the shuffle,
             // but does depend on randomness in the stochastic approximation code
-            BOOST_CHECK(testWallet.SelectCoinsMinConf(50 * COIN, filter_standard, vCoins, setCoinsRet , nValueRet));
-            BOOST_CHECK(testWallet.SelectCoinsMinConf(50 * COIN, filter_standard, vCoins, setCoinsRet2, nValueRet));
+            BOOST_CHECK(testWallet.SelectCoinsMinConf(50 * COIN, filter_standard, vCoins, setCoinsRet , nValueRet, coin_selection_params, bnb_used));
+            BOOST_CHECK(testWallet.SelectCoinsMinConf(50 * COIN, filter_standard, vCoins, setCoinsRet2, nValueRet, coin_selection_params, bnb_used));
             BOOST_CHECK(!equal_sets(setCoinsRet, setCoinsRet2));
 
             int fails = 0;
@@ -445,8 +450,8 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
             {
                 // selecting 1 from 100 identical coins depends on the shuffle; this test will fail 1% of the time
                 // run the test RANDOM_REPEATS times and only complain if all of them fail
-                BOOST_CHECK(testWallet.SelectCoinsMinConf(COIN, filter_standard, vCoins, setCoinsRet , nValueRet));
-                BOOST_CHECK(testWallet.SelectCoinsMinConf(COIN, filter_standard, vCoins, setCoinsRet2, nValueRet));
+                BOOST_CHECK(testWallet.SelectCoinsMinConf(COIN, filter_standard, vCoins, setCoinsRet , nValueRet, coin_selection_params, bnb_used));
+                BOOST_CHECK(testWallet.SelectCoinsMinConf(COIN, filter_standard, vCoins, setCoinsRet2, nValueRet, coin_selection_params, bnb_used));
                 if (equal_sets(setCoinsRet, setCoinsRet2))
                     fails++;
             }
@@ -466,8 +471,8 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
             {
                 // selecting 1 from 100 identical coins depends on the shuffle; this test will fail 1% of the time
                 // run the test RANDOM_REPEATS times and only complain if all of them fail
-                BOOST_CHECK(testWallet.SelectCoinsMinConf(90*CENT, filter_standard, vCoins, setCoinsRet , nValueRet));
-                BOOST_CHECK(testWallet.SelectCoinsMinConf(90*CENT, filter_standard, vCoins, setCoinsRet2, nValueRet));
+                BOOST_CHECK(testWallet.SelectCoinsMinConf(90*CENT, filter_standard, vCoins, setCoinsRet , nValueRet, coin_selection_params, bnb_used));
+                BOOST_CHECK(testWallet.SelectCoinsMinConf(90*CENT, filter_standard, vCoins, setCoinsRet2, nValueRet, coin_selection_params, bnb_used));
                 if (equal_sets(setCoinsRet, setCoinsRet2))
                     fails++;
             }
@@ -481,6 +486,7 @@ BOOST_AUTO_TEST_CASE(ApproximateBestSubset)
 {
     CoinSet setCoinsRet;
     CAmount nValueRet;
+    bool bnb_used;
 
     LOCK(testWallet.cs_wallet);
 
@@ -491,11 +497,55 @@ BOOST_AUTO_TEST_CASE(ApproximateBestSubset)
         add_coin(1000 * COIN);
     add_coin(3 * COIN);
 
-    BOOST_CHECK(testWallet.SelectCoinsMinConf(1003 * COIN, filter_standard, vCoins, setCoinsRet, nValueRet));
+    BOOST_CHECK(testWallet.SelectCoinsMinConf(1003 * COIN, filter_standard, vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used));
     BOOST_CHECK_EQUAL(nValueRet, 1003 * COIN);
     BOOST_CHECK_EQUAL(setCoinsRet.size(), 2U);
 
     empty_wallet();
 }
 
+// Tests that with the ideal conditions, the coin selector will always be able to find a solution that can pay the target value
+BOOST_AUTO_TEST_CASE(SelectCoins_test)
+{
+    // Random generator stuff
+    std::default_random_engine generator;
+    std::exponential_distribution<double> distribution (100);
+    FastRandomContext rand;
+
+    // Output stuff
+    CAmount out_value = 0;
+    CoinSet out_set;
+    CAmount target = 0;
+    bool bnb_used;
+
+    // Run this test 100 times
+    for (int i = 0; i < 100; ++i)
+    {
+        // Reset
+        out_value = 0;
+        target = 0;
+        out_set.clear();
+        empty_wallet();
+
+        // Make a wallet with 1000 exponentially distributed random inputs
+        for (int j = 0; j < 1000; ++j)
+        {
+            add_coin((CAmount)(distribution(generator)*10000000));
+        }
+
+        // Generate a random fee rate in the range of 100 - 400
+        CFeeRate rate(rand.randrange(300) + 100);
+
+        // Generate a random target value between 1000 and wallet balance
+        target = rand.randrange(balance - 1000) + 1000;
+
+        // Perform selection
+        CoinSelectionParams coin_selection_params_knapsack(false, 34, 148, CFeeRate(0), 0);
+        CoinSelectionParams coin_selection_params_bnb(true, 34, 148, CFeeRate(0), 0);
+        BOOST_CHECK(testWallet.SelectCoinsMinConf(target, filter_standard, vCoins, out_set, out_value, coin_selection_params_bnb, bnb_used) ||
+                    testWallet.SelectCoinsMinConf(target, filter_standard, vCoins, out_set, out_value, coin_selection_params_knapsack, bnb_used));
+        BOOST_CHECK_GE(out_value, target);
+    }
+}
+
 BOOST_AUTO_TEST_SUITE_END()