bitcoind-tests: Add basic test

Add infrastructure for testing and add a `basic` test that uses the PSBT
v2 to create a transaction ready to hand off to a signer.

bitcoind-tests/Cargo.toml

@@ -5,9 +5,12 @@ authors = ["Tobin C. Harding <[email protected]>"]
 license = "CC0-1.0"
 edition = "2021"
 
-# This crate is only used for testing, no features or dependencies.
-
-[dev-dependencies]
+[dependencies]
 anyhow = "1"
+bitcoin = { version = "0.31.0", features = ["rand-std"] }
 bitcoind = { version = "0.34.1", features = ["25_1"] }
-psbt-v2 = { path = "..", features = ["std"] }
+secp256k1 = { version = "0.28.2", features = ["global-context", "rand-std"] }
+psbt-v2 = { path = "..", features = ["std", "miniscript-std"] }
+
+[dev-dependencies]
+

bitcoind-tests/src/client.rs

@@ -0,0 +1,185 @@
+// SPDX-License-Identifier: CC0-1.0
+
+//! Implements a client that wraps the `bitcoind` client (which uses the `bitcoincore-rpc` client).
+//!
+//! Adds balance tracking that is specific to how Bitcoin Core works on regtest.
+
+// We depend upon and import directly from bitcoin because this module is not concerned with PSBT
+// i.e., it is lower down the stack than the psbt_v2 crate.
+use bitcoin::{consensus, Address, Amount, Network, Transaction, Txid};
+use bitcoind::bitcoincore_rpc::bitcoincore_rpc_json::{AddressType, GetBlockchainInfoResult};
+use bitcoind::bitcoincore_rpc::RpcApi;
+use bitcoind::BitcoinD;
+
+const NETWORK: Network = Network::Regtest;
+const FIFTY_BTC: Amount = Amount::from_int_btc(50);
+
+/// A custom bitcoind client.
+pub struct Client {
+    /// Handle for the regtest `bitcoind` instance.
+    bitcoind: BitcoinD,
+    /// This is public so we don't have to handle the complexity of know if send/receives are
+    /// to/from the Core controlled wallet or somewhere else. User is required to manage this.
+    pub balance: BalanceTracker,
+}
+
+impl Client {
+    /// Creates a new [`Client`].
+    pub fn new() -> anyhow::Result<Self> {
+        let bitcoind = BitcoinD::from_downloaded()?;
+        let balance = BalanceTracker::zero();
+
+        let client = Client { bitcoind, balance };
+
+        // Sanity check.
+        assert_eq!(0, client.get_blockchain_info().unwrap().blocks);
+
+        client.mine_blocks(100)?;
+        assert_eq!(100, client.get_blockchain_info().unwrap().blocks);
+
+        client.assert_balance_is_as_expected()?; // Sanity check.
+
+        Ok(client)
+    }
+
+    /// Mines a block to a new address controlled by the currently loaded Bitcoin Core wallet.
+    pub fn mine_a_block(&mut self) -> anyhow::Result<()> {
+        self.mine_blocks(1)?;
+        self.balance.mine_a_block();
+        Ok(())
+    }
+
+    /// Returns the amount in the balance tracker.
+    pub fn tracked_balance(&self) -> Amount { self.balance.balance }
+
+    #[track_caller]
+    pub fn assert_balance_is_as_expected(&self) -> anyhow::Result<()> {
+        let balance = self.balance()?;
+        self.balance.assert(balance);
+        Ok(())
+    }
+
+    /// Calls through to bitcoincore_rpc client.
+    pub fn get_blockchain_info(&self) -> anyhow::Result<GetBlockchainInfoResult> {
+        let client = &self.bitcoind.client;
+        Ok(client.get_blockchain_info()?)
+    }
+
+    /// Gets an address controlled by the currently loaded Bitcoin Core wallet (via `bitcoind`).
+    pub fn core_wallet_controlled_address(&self) -> anyhow::Result<Address> {
+        let client = &self.bitcoind.client;
+        let label = None;
+        let address_type = Some(AddressType::Bech32m);
+        let address = client.get_new_address(label, address_type)?.require_network(NETWORK)?;
+        Ok(address)
+    }
+
+    pub fn balance(&self) -> anyhow::Result<Amount> {
+        let client = &self.bitcoind.client;
+        let minconf = None; // What is this?
+        let include_watchonly = None;
+        Ok(client.get_balance(minconf, include_watchonly)?)
+    }
+
+    /// Mines `n` blocks to a new address controlled by the currently loaded Bitcoin Core wallet.
+    fn mine_blocks(&self, n: u64) -> anyhow::Result<()> {
+        let client = &self.bitcoind.client;
+        // Generate to an address controlled by the bitcoind wallet and wait for funds to mature.
+        let address = self.core_wallet_controlled_address()?;
+        let _ = client.generate_to_address(n, &address)?;
+
+        Ok(())
+    }
+
+    /// Send `amount` to `address` setting all other `bitcoincore_prc::send_to_address` args to `None`.
+    ///
+    /// Caller required to update balance (ie, call self.balance.send()).
+    pub fn send(&self, amount: Amount, address: &Address) -> anyhow::Result<Txid> {
+        let client = &self.bitcoind.client;
+
+        let comment = None;
+        let comment_to = None;
+        let subtract_fee = None;
+        let replacable = None;
+        let confirmation_target = None;
+        let estimate_mode = None;
+
+        let txid = client.send_to_address(
+            address,
+            amount,
+            comment,
+            comment_to,
+            subtract_fee,
+            replacable,
+            confirmation_target,
+            estimate_mode,
+        )?;
+
+        Ok(txid)
+    }
+
+    pub fn get_transaction(&self, txid: &Txid) -> anyhow::Result<Transaction> {
+        let client = &self.bitcoind.client;
+        let include_watchonly = None;
+        let res = client.get_transaction(txid, include_watchonly)?;
+        let tx: Transaction = consensus::encode::deserialize(&res.hex)?;
+        Ok(tx)
+    }
+
+    pub fn send_raw_transaction(&self, tx: &Transaction) -> anyhow::Result<Txid> {
+        let client = &self.bitcoind.client;
+        let hex = consensus::encode::serialize_hex(&tx);
+        let txid = client.send_raw_transaction(hex)?;
+        Ok(txid)
+    }
+}
+
+/// Tracks the amount we expect the Core controlled wallet to hold.
+///
+/// We are sending whole bitcoin amounts back and forth, as a rough check that the transactions have
+/// been mined we test against the integer floor of the amount, this allows us to not track fees.
+pub struct BalanceTracker {
+    balance: Amount,
+}
+
+impl BalanceTracker {
+    /// Creates a new `BalanceTracker`.
+    fn zero() -> Self { Self { balance: Amount::ZERO } }
+
+    /// Everytime we mine a block we release another coinbase reward.
+    fn mine_a_block(&mut self) { self.balance += FIFTY_BTC }
+
+    /// Mimic sending, deduct token fee amount.
+    pub fn send_to_self(&mut self) { self.send(Amount::ZERO) }
+
+    /// Update balance by sending `amount`.
+    pub fn send(&mut self, amount: Amount) {
+        // 1000 mimics some fee amount, the exact amount is not important
+        // because we ignore everything after the decimal place.
+        self.balance = self.balance - amount - Amount::from_sat(1000);
+    }
+
+    /// Update balance by receiving `amount`.
+    pub fn receive(&mut self, amount: Amount) {
+        // 1000 mimics some fee amount, the exact amount is not important
+        // because we ignore everything after the decimal place.
+        self.balance = self.balance + amount + FIFTY_BTC - Amount::from_sat(1000)
+    }
+
+    /// Asserts balance against `want` ignoring everything except
+    /// whole bitcoin, this allows us to ignore fees.
+    #[track_caller]
+    fn assert(&self, want: Amount) {
+        let got = floor(self.balance);
+        let floor_want = floor(want);
+        if got != floor_want {
+            panic!("We have {} but were expecting to have {} ({})", got, floor_want, want);
+        }
+    }
+}
+
+fn floor(x: Amount) -> Amount {
+    let one = 100_000_000;
+    let sats = x.to_sat();
+    Amount::from_sat(sats / one * one)
+}

bitcoind-tests/src/lib.rs

@@ -0,0 +1,7 @@
+//! Tools to help with testing against Bitcoin Core using [`bitcoind`] and [`bitcoincore-rpc`].
+//!
+//! [`bitcoind`]: <https://github.com/rust-bitcoin/bitcoind>
+//! [`bitcoincore-rpc`]: <https://github.com/rust-bitcoin/rust-bitcoincore-rpc/>
+
+/// A wrapper around the `bitcoind` client.
+pub mod client;

bitcoind-tests/tests/basic.rs

@@ -0,0 +1,108 @@
+//! A basic PSBT test, a single entity using PSBTv2 to create and sign a transaction.
+
+use core::str::FromStr;
+
+// Only depend on `psbt` (and `bitcoind_tests`) because we are explicitly testing the `psbt_v2` crate.
+use bitcoind_tests::client::Client;
+use psbt::bitcoin::{Address, Amount, Network, OutPoint, PublicKey, Script, Transaction, TxOut};
+use psbt::v2::{Constructor, InputBuilder, Modifiable, OutputBuilder};
+// The `psbt_v2` crate, as we expect downstream to use it
+// E.g., in manifest file `use psbt = { package = "psbt_v2" ... }`
+use psbt_v2 as psbt;
+
+const NETWORK: Network = Network::Regtest;
+const TWO_BTC: Amount = Amount::from_int_btc(2);
+const ONE_BTC: Amount = Amount::from_int_btc(1);
+const FEE: Amount = Amount::from_sat(1000); // Arbitrary fee.
+
+#[test]
+fn basic() -> anyhow::Result<()> {
+    // Create the RPC client and a wallet controlled by Bitcoin Core.
+    let mut client = Client::new()?;
+    // Fund the wallet with 50 BTC.
+    client.mine_a_block()?;
+
+    // Create an entity who wishes to use PSBTs to create a transaction.
+    let alice = Alice::new();
+    let alice_address = alice.address();
+
+    // Send coin from the Core controlled wallet to Alice.
+    let txid = client.send(TWO_BTC, &alice.address())?;
+    client.balance.send(TWO_BTC);
+    client.mine_a_block()?;
+    client.assert_balance_is_as_expected()?;
+
+    // Get the chain data for Alice's UTXO shew wishes to spend from.
+    let tx = client.get_transaction(&txid)?;
+    let utxos = tx.outputs_encumbered_by(&alice_address.script_pubkey());
+    assert_eq!(utxos.len(), 1);
+    let (out_point, fund) = utxos[0];
+
+    let receiver = client.core_wallet_controlled_address()?;
+    let spend_amount = ONE_BTC;
+    let change_amount = fund.value - spend_amount - FEE;
+
+    let constructor = Constructor::<Modifiable>::default();
+
+    let spend_output = TxOut { value: spend_amount, script_pubkey: receiver.script_pubkey() };
+    let change_output = TxOut {
+        value: change_amount,
+        // Since this is a basic example, just send back to same address.
+        script_pubkey: alice_address.script_pubkey(),
+    };
+
+    let input = InputBuilder::new(&out_point).segwit_fund(fund.clone()).build();
+    let spend = OutputBuilder::new(spend_output).build();
+    let change = OutputBuilder::new(change_output).build();
+
+    let psbt = constructor.input(input).output(spend).output(change).psbt()?;
+    psbt.determine_lock_time()?;
+
+    // Serialize and pass to hardware wallet to sign.
+    println!("PSBTv2 ready for signing\n{:#?}", psbt);
+
+    Ok(())
+}
+
+pub trait TransactionExt {
+    /// Returns a list of UTXOs in this transaction that are encumbered by `script_pubkey`.
+    fn outputs_encumbered_by(&self, script_pubkey: &Script) -> Vec<(OutPoint, &TxOut)>;
+}
+
+impl TransactionExt for Transaction {
+    fn outputs_encumbered_by(&self, script_pubkey: &Script) -> Vec<(OutPoint, &TxOut)> {
+        let mut utxos = vec![];
+        for (index, utxo) in self.output.iter().enumerate() {
+            if &utxo.script_pubkey == script_pubkey {
+                let out_point = OutPoint { txid: self.txid(), vout: index as u32 };
+
+                utxos.push((out_point, utxo));
+            }
+        }
+        utxos
+    }
+}
+
+/// A super basic entity with a single public key.
+pub struct Alice {
+    /// The single public key.
+    public_key: PublicKey,
+}
+
+impl Alice {
+    /// Creates a new Alice.
+    pub fn new() -> Self {
+        // An arbitrary public key, assume the secret key is held by another entity.
+        let public_key = PublicKey::from_str(
+            "032e58afe51f9ed8ad3cc7897f634d881fdbe49a81564629ded8156bebd2ffd1af",
+        )
+        .unwrap();
+
+        Alice { public_key }
+    }
+
+    /// Returns a bech32m address from a key Alice controls.
+    pub fn address(&self) -> Address {
+        Address::p2wpkh(&self.public_key, NETWORK).expect("uncompressed key")
+    }
+}