Add proptest for arbitrary target

prop/src/main.rs

@@ -8,6 +8,8 @@ use proptest::prelude::*;
 use bitcoin_coin_selection::select_coins_bnb;
 use bitcoin_coin_selection::WeightedUtxo;
 
+use std::str::FromStr;
+
 #[derive(Clone, Debug)]
 pub struct Utxo {
     output: TxOut,
@@ -43,6 +45,26 @@ fn build_pool(vec: &mut Vec<(u8, bool)>) -> Vec<Utxo> {
     .collect()
 }
 
+fn build_linear_pool() -> Vec<Utxo> {
+    (1..10)
+        .map(|i| format!("{} cBTC", i))
+        .map(|s| Amount::from_str(&s).unwrap())
+        .map(|a| {
+            let output = TxOut {
+                value: a,
+                script_pubkey: ScriptBuf::new()
+            };
+
+            let satisfaction_weight = Weight::ZERO;
+
+            Utxo {
+                output,
+                satisfaction_weight
+            }
+        })
+    .collect()
+}
+
 fn create_target_amt_from(pool: &Vec<(u8, bool)>) -> Amount {
     pool.iter().fold(Amount::ZERO, |acc, (u, b)|
         {
@@ -61,6 +83,7 @@ proptest! {
     // later, that it does not overflow.
     fn test_bnb_arbitrary_pool(ref mut vec in any::<Vec<(u8, bool)>>()) {
         vec.truncate(10);
+
         let pool: Vec<_> = build_pool(vec);
         let target = create_target_amt_from(&vec);
 
@@ -77,8 +100,28 @@ proptest! {
         let sum: Amount = selection.into_iter().sum();
         assert_eq!(target, sum);
     }
+
+    #[test]
+    fn test_bnb_arbitrary_target(t in any::<u64>()) {
+        let target_str = format!("{} cBTC", t % 10);
+        let target = Amount::from_str(&target_str).unwrap();
+        let pool = build_linear_pool();
+
+        let selection_sum: Amount =
+            select_coins_bnb(
+                target,
+                Amount::ZERO,
+                FeeRate::ZERO,
+                FeeRate::ZERO,
+                &pool)
+            .unwrap()
+            .map(|i| i.value()).sum();
+
+        assert_eq!(selection_sum, target);
+    }
 }
 
 fn main() {
     test_bnb_arbitrary_pool();
+    test_bnb_arbitrary_target();
 }