zcash_client_sqlite: Add test that exposes the no-change bug

zcash_client_sqlite/src/wallet/transact.rs

@@ -154,6 +154,7 @@ mod tests {
     use zcash_primitives::{
         block::BlockHash,
         consensus::BlockHeight,
+        legacy::TransparentAddress,
         note_encryption::try_sapling_output_recovery,
         prover::TxProver,
         transaction::{components::Amount, Transaction},
@@ -665,4 +666,54 @@ mod tests {
         // Neither transaction output is decryptable by the sender.
         assert!(send_and_recover_with_policy(&mut db_write, OvkPolicy::Discard).is_none());
     }
+
+    #[test]
+    fn create_to_address_succeeds_to_t_addr_zero_change() {
+        let cache_file = NamedTempFile::new().unwrap();
+        let db_cache = BlockDB(Connection::open(cache_file.path()).unwrap());
+        init_cache_database(&db_cache).unwrap();
+
+        let data_file = NamedTempFile::new().unwrap();
+        let db_data = WalletDB::for_path(data_file.path(), tests::network()).unwrap();
+        init_wallet_db(&db_data).unwrap();
+
+        // Add an account to the wallet
+        let extsk = ExtendedSpendingKey::master(&[]);
+        let extfvk = ExtendedFullViewingKey::from(&extsk);
+        init_accounts_table(&db_data, &[extfvk.clone()]).unwrap();
+
+        // Add funds to the wallet in a single note
+        let value = Amount::from_u64(51000).unwrap();
+        let (cb, _) = fake_compact_block(
+            sapling_activation_height(),
+            BlockHash([0; 32]),
+            extfvk.clone(),
+            value,
+        );
+        insert_into_cache(&db_cache, &cb);
+        let mut db_write = db_data.get_update_ops().unwrap();
+        scan_cached_blocks(&tests::network(), &db_cache, &mut db_write, None).unwrap();
+
+        // Verified balance matches total balance
+        let (_, anchor_height) = (&db_data).get_target_and_anchor_heights().unwrap().unwrap();
+        assert_eq!(get_balance(&db_data, AccountId(0)).unwrap(), value);
+        assert_eq!(
+            get_balance_at(&db_data, AccountId(0), anchor_height).unwrap(),
+            value
+        );
+
+        let to = TransparentAddress::PublicKey([7; 20]).into();
+        create_spend_to_address(
+            &mut db_write,
+            &tests::network(),
+            test_prover(),
+            AccountId(0),
+            &extsk,
+            &to,
+            Amount::from_u64(50000).unwrap(),
+            None,
+            OvkPolicy::Sender,
+        )
+        .unwrap();
+    }
 }