zakura-client-backend 0.1.0-rc2

//! Utilities for testing wallets based upon the [`crate::data_api`] traits.

use std::{
    collections::{BTreeMap, HashMap, HashSet},
    convert::Infallible,
    fmt,
    hash::Hash,
    num::{NonZeroU8, NonZeroU32, NonZeroU64},
};

#[cfg(feature = "pczt")]
use super::wallet::{create_pczt_from_proposal, extract_and_store_transaction_from_pczt};
use assert_matches::assert_matches;
use group::ff::Field;
use incrementalmerkletree::{Marking, Retention};
use nonempty::NonEmpty;
use rand_08::{CryptoRng as CryptoRng08, Rng as Rng08, RngCore as RngCore08, SeedableRng};
use rand_chacha::ChaChaRng;
use secrecy::{ExposeSecret, Secret, SecretVec};
use shardtree::{
    ShardTree,
    error::ShardTreeError,
    store::{ShardStore as _, memory::MemoryShardStore},
};
use subtle::ConditionallySelectable;
#[cfg(feature = "transparent-inputs")]
use {
    super::{
        CoinbaseFilter, TransactionsInvolvingAddress, TransparentBalances,
        wallet::{
            input_selection::ShieldingSelector, propose_shielding, propose_shielding_coinbase,
            shield_transparent_funds,
        },
    },
    crate::wallet::TransparentAddressMetadata,
    ::transparent::address::TransparentAddress,
    zcash_keys::keys::transparent::gap_limits::GapLimits,
};

use ::sapling::{
    note_encryption::{SaplingDomain, sapling_note_encryption},
    prover::mock::{MockOutputProver, MockSpendProver},
    util::generate_random_rseed,
    zip32::DiversifiableFullViewingKey,
};
use zcash_address::ZcashAddress;
use zcash_keys::{
    address::{Address, UnifiedAddress},
    keys::{UnifiedAddressRequest, UnifiedFullViewingKey, UnifiedSpendingKey},
};
use zcash_note_encryption::Domain;
use zcash_primitives::{
    block::BlockHash,
    transaction::{Transaction, TxId, components::sapling::zip212_enforcement, fees::FeeRule},
};
#[cfg(feature = "pczt")]
use zcash_proofs::prover::LocalTxProver;
use zcash_protocol::{
    ShieldedPool,
    consensus::{self, BlockHeight, Network, NetworkUpgrade, Parameters as _},
    local_consensus::LocalNetwork,
    memo::{Memo, MemoBytes},
    value::{ZatBalance, Zatoshis},
};
#[cfg(feature = "transparent-key-import")]
use zcash_script::script;
use zip32::DiversifierIndex;
use zip321::Payment;
#[cfg(feature = "orchard")]
use {
    super::ORCHARD_SHARD_HEIGHT,
    crate::proto::compact_formats::CompactOrchardAction,
    ::orchard::{
        note::{ExtractedNoteCommitment, Note as OrchardNote, NoteVersion, RandomSeed, Rho},
        note_encryption::{IronwoodDomain, IronwoodNoteEncryption},
        tree::MerkleHashOrchard,
    },
    group::ff::PrimeField,
    pasta_curves::pallas,
    zcash_note_encryption::ShieldedOutput,
};

use super::{
    Account, AccountBalance, AccountBirthday, AccountMeta, AccountPurpose, AccountSource,
    AddressInfo, BlockMetadata, DecryptedTransaction, InputSource, NoteFilter, NullifierQuery,
    ReceivedNotes, ReceivedTransactionOutput, SAPLING_SHARD_HEIGHT, ScannedBlock, SeedRelevance,
    SentTransaction, TransactionDataRequest, TransactionStatus, WalletCommitmentTrees, WalletRead,
    WalletSummary, WalletTest, WalletWrite, Zip32Derivation,
    anchor_retention::AnchorRetentionInterval,
    chain::{BlockSource, ChainState, CommitmentTreeRoot, ScanSummary, scan_cached_blocks},
    error::Error,
    scanning::{ScanPriority, ScanRange},
    wallet::{
        ConfirmationsPolicy, SpendingKeys, create_proposed_transactions,
        input_selection::{
            GreedyInputSelector, InputSelector, LockFilter, LockedInputPolicy, SpendPolicy,
        },
        propose_send_max_transfer, propose_standard_transfer_to_address, propose_transfer,
    },
};

/// A deterministic test RNG compatible with both the legacy Rand 0.8 test
/// utilities and the Rand 0.10 traits used by the Zakura RC3 crypto crates.
#[derive(Clone, Debug)]
pub struct TestRng(ChaChaRng);

impl TestRng {
    pub fn seed_from_u64(seed: u64) -> Self {
        Self(ChaChaRng::seed_from_u64(seed))
    }
}

impl RngCore08 for TestRng {
    fn next_u32(&mut self) -> u32 {
        self.0.next_u32()
    }

    fn next_u64(&mut self) -> u64 {
        self.0.next_u64()
    }

    fn fill_bytes(&mut self, dest: &mut [u8]) {
        self.0.fill_bytes(dest);
    }

    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), rand_08::Error> {
        self.0.try_fill_bytes(dest)
    }
}

impl CryptoRng08 for TestRng {}

impl rand::rand_core::TryRng for TestRng {
    type Error = Infallible;

    fn try_next_u32(&mut self) -> Result<u32, Self::Error> {
        Ok(self.0.next_u32())
    }

    fn try_next_u64(&mut self) -> Result<u64, Self::Error> {
        Ok(self.0.next_u64())
    }

    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Self::Error> {
        self.0.fill_bytes(dest);
        Ok(())
    }
}

impl rand::rand_core::TryCryptoRng for TestRng {}

/// The RNG capabilities required by test helpers that cross the Rand 0.8/0.10
/// boundary.
pub trait TestRngCore: RngCore08 + CryptoRng08 + rand::Rng + rand::rand_core::CryptoRng {}

impl<R> TestRngCore for R where R: RngCore08 + CryptoRng08 + rand::Rng + rand::rand_core::CryptoRng {}

/// Generates a random frontier and its prior subtree roots using an explicit
/// node generator.
///
/// This preserves the behavior of
/// `Frontier::random_with_prior_subtree_roots` without requiring the node's
/// random distribution to use the Rand 0.8 version fixed by
/// `incrementalmerkletree`.
pub fn random_frontier_with_prior_subtree_roots<H, R, const DEPTH: u8>(
    rng: &mut R,
    tree_size: u64,
    subtree_depth: NonZeroU8,
    mut random_node: impl FnMut(&mut R) -> H,
) -> (Vec<H>, incrementalmerkletree::frontier::Frontier<H, DEPTH>)
where
    H: incrementalmerkletree::Hashable + Clone,
{
    use incrementalmerkletree::{Level, Position, frontier::Frontier};

    assert!(tree_size <= 2u64.checked_pow(DEPTH.into()).unwrap());
    let Some(tree_size) = NonZeroU64::new(tree_size) else {
        return (vec![], Frontier::empty());
    };

    let prior_subtree_count: u64 = u64::from(tree_size) >> u8::from(subtree_depth);
    let prior_roots: Vec<H> = core::iter::repeat_with(|| random_node(rng))
        .take(prior_subtree_count as usize)
        .collect();

    let position = Position::from(u64::from(tree_size) - 1);
    let leaf = random_node(rng);
    let mut ommers: Vec<H> = core::iter::repeat_with(|| random_node(rng))
        .take(position.past_ommer_count().into())
        .collect();

    if !prior_roots.is_empty() {
        let subtree_root_level = Level::from(u8::from(subtree_depth));
        let mut replacement_ommers: Vec<(Level, H)> = vec![];
        let mut roots_iter = prior_roots.iter();

        loop {
            if let Some(top) = replacement_ommers.pop() {
                if let Some(prev) = replacement_ommers.pop() {
                    if top.0 == prev.0 {
                        replacement_ommers.push((top.0 + 1, H::combine(top.0, &prev.1, &top.1)));
                        continue;
                    } else {
                        replacement_ommers.push(prev);
                    }
                }

                if let Some(root) = roots_iter.next() {
                    if top.0 == subtree_root_level {
                        replacement_ommers.push((
                            subtree_root_level + 1,
                            H::combine(subtree_root_level, &top.1, root),
                        ));
                    } else {
                        replacement_ommers.push(top);
                        replacement_ommers.push((subtree_root_level, root.clone()));
                    }
                } else {
                    replacement_ommers.push(top);
                    break;
                }
            } else if let Some(root) = roots_iter.next() {
                replacement_ommers.push((subtree_root_level, root.clone()));
            } else {
                break;
            }
        }

        let ommer_count = ommers.len();
        for (idx, (_, ommer)) in replacement_ommers.into_iter().enumerate() {
            ommers[ommer_count - (idx + 1)] = ommer;
        }
    }

    (
        prior_roots,
        Frontier::from_parts(position, leaf, ommers).expect("generated frontier is valid"),
    )
}

#[cfg(feature = "pczt")]
fn real_test_prover() -> &'static LocalTxProver {
    use std::sync::OnceLock;

    static PROVER: OnceLock<LocalTxProver> = OnceLock::new();
    PROVER.get_or_init(LocalTxProver::bundled)
}
use crate::{
    data_api::{
        MaxSpendMode, OutputLockStore, TargetValue,
        error::{LockError, RewindError},
        wallet::TargetHeight,
    },
    fees::{
        ChangeStrategy, DustOutputPolicy, StandardFeeRule,
        standard::{self, SingleOutputChangeStrategy},
    },
    proposal::Proposal,
    proto::compact_formats::{
        self, CompactBlock, CompactSaplingOutput, CompactSaplingSpend, CompactTx,
    },
    wallet::{
        LockOwner, Note, NoteId, OutputRef, OvkPolicy, ReceivedNote, WalletTransparentOutput,
    },
};

pub mod pool;
pub mod sapling;

#[cfg(feature = "orchard")]
pub mod orchard;
#[cfg(feature = "transparent-inputs")]
pub mod transparent;

/// Information about a transaction that the wallet is interested in.
#[derive(Debug)]
pub struct TransactionSummary<AccountId> {
    account_id: AccountId,
    txid: TxId,
    expiry_height: Option<BlockHeight>,
    mined_height: Option<BlockHeight>,
    account_value_delta: ZatBalance,
    total_spent: Zatoshis,
    total_received: Zatoshis,
    fee_paid: Option<Zatoshis>,
    spent_note_count: usize,
    has_change: bool,
    sent_note_count: usize,
    received_note_count: usize,
    memo_count: usize,
    expired_unmined: bool,
    is_shielding: bool,
    pool_crossing_value: Option<Zatoshis>,
}

impl<AccountId> TransactionSummary<AccountId> {
    /// Constructs a `TransactionSummary` from its parts.
    ///
    /// See the documentation for each getter method below to determine how each method
    /// argument should be prepared.
    #[allow(clippy::too_many_arguments)]
    pub fn from_parts(
        account_id: AccountId,
        txid: TxId,
        expiry_height: Option<BlockHeight>,
        mined_height: Option<BlockHeight>,
        account_value_delta: ZatBalance,
        total_spent: Zatoshis,
        total_received: Zatoshis,
        fee_paid: Option<Zatoshis>,
        spent_note_count: usize,
        has_change: bool,
        sent_note_count: usize,
        received_note_count: usize,
        memo_count: usize,
        expired_unmined: bool,
        is_shielding: bool,
        pool_crossing_value: Option<Zatoshis>,
    ) -> Self {
        Self {
            account_id,
            txid,
            expiry_height,
            mined_height,
            account_value_delta,
            total_spent,
            total_received,
            fee_paid,
            spent_note_count,
            has_change,
            sent_note_count,
            received_note_count,
            memo_count,
            expired_unmined,
            is_shielding,
            pool_crossing_value,
        }
    }

    /// Returns the wallet-internal ID for the account that this transaction was received
    /// by or sent from.
    pub fn account_id(&self) -> &AccountId {
        &self.account_id
    }

    /// Returns the transaction's ID.
    pub fn txid(&self) -> TxId {
        self.txid
    }

    /// Returns the expiry height of the transaction, if known.
    ///
    /// - `None` means that the expiry height is unknown.
    /// - `Some(0)` means that the transaction does not expire.
    pub fn expiry_height(&self) -> Option<BlockHeight> {
        self.expiry_height
    }

    /// Returns the height of the mined block containing this transaction, or `None` if
    /// the wallet has not yet observed the transaction to be mined.
    pub fn mined_height(&self) -> Option<BlockHeight> {
        self.mined_height
    }

    /// Returns the net change in balance that this transaction caused to the account.
    ///
    /// For example, an account-internal transaction (such as a shielding operation) would
    /// show `-fee_paid` as the account value delta.
    pub fn account_value_delta(&self) -> ZatBalance {
        self.account_value_delta
    }

    /// Returns the total value of notes spent by the account in this transaction.
    pub fn total_spent(&self) -> Zatoshis {
        self.total_spent
    }

    /// Returns the total value of notes received by the account in this transaction.
    pub fn total_received(&self) -> Zatoshis {
        self.total_received
    }

    /// Returns the fee paid by this transaction, if known.
    pub fn fee_paid(&self) -> Option<Zatoshis> {
        self.fee_paid
    }

    /// Returns the number of notes spent by the account in this transaction.
    pub fn spent_note_count(&self) -> usize {
        self.spent_note_count
    }

    /// Returns `true` if the account received a change note as part of this transaction.
    ///
    /// This implies that the transaction was (at least in part) sent from the account.
    pub fn has_change(&self) -> bool {
        self.has_change
    }

    /// Returns the number of notes created in this transaction that were sent to a
    /// wallet-external address.
    pub fn sent_note_count(&self) -> usize {
        self.sent_note_count
    }

    /// Returns the number of notes created in this transaction that were received by the
    /// account.
    pub fn received_note_count(&self) -> usize {
        self.received_note_count
    }

    /// Returns `true` if, from the wallet's current view of the chain, this transaction
    /// expired before it was mined.
    pub fn expired_unmined(&self) -> bool {
        self.expired_unmined
    }

    /// Returns the number of non-empty memos viewable by the account in this transaction.
    pub fn memo_count(&self) -> usize {
        self.memo_count
    }

    /// Returns `true` if this is detectably a shielding transaction.
    ///
    /// Specifically, `true` means that at a minimum:
    /// - All of the wallet-spent and wallet-received notes are consistent with a
    ///   shielding transaction.
    /// - The transaction contains at least one wallet-spent output.
    /// - The transaction contains at least one wallet-received note.
    /// - We do not know about any external outputs of the transaction.
    ///
    /// There may be some shielding transactions for which this method returns `false`,
    /// due to them not being detectable by the wallet as shielding transactions under the
    /// above metrics.
    pub fn is_shielding(&self) -> bool {
        self.is_shielding
    }

    /// Returns `true` if this is detectably a wallet-internal transfer that moves the
    /// account's own funds between shielded pools (for example, a ZIP 318
    /// Orchard -> Ironwood migration transfer).
    ///
    /// Specifically, `true` means that at a minimum:
    /// - Every wallet-spent note and wallet-received output is shielded.
    /// - The transaction spends at least one of the account's notes.
    /// - At least one output was received in a pool the account spent nothing from.
    /// - We do not know about any external outputs of the transaction.
    ///
    /// A payment that returns value to one of the wallet's own addresses is classified
    /// once the wallet has observed the returned output (which the scanner marks as
    /// change); while such a transaction is unmined it is treated as an ordinary payment.
    ///
    /// This is exactly the condition that [`Self::pool_crossing_value`] is `Some`; the
    /// crossed amount is what identifies the transaction, so it is the only thing stored.
    pub fn is_pool_crossing(&self) -> bool {
        self.pool_crossing_value.is_some()
    }

    /// Returns the total value received in pools the account did not spend from, which
    /// is the amount that crossed pools, when this is a pool-crossing transaction as described
    /// by [`Self::is_pool_crossing`], or `None` otherwise.
    pub fn pool_crossing_value(&self) -> Option<Zatoshis> {
        self.pool_crossing_value
    }
}

/// Metadata about a block generated by [`TestState`].
#[derive(Clone, Debug)]
pub struct CachedBlock {
    chain_state: ChainState,
    sapling_end_size: u32,
    orchard_end_size: u32,
    ironwood_end_size: u32,
}

impl CachedBlock {
    /// Produces metadata for a block "before shielded time", when the Sapling, Orchard, and
    /// Ironwood trees were (by definition) empty.
    ///
    /// `block_height` must be a height before Sapling activation (and therefore also
    /// before NU5 activation).
    pub fn none(block_height: BlockHeight) -> Self {
        Self {
            chain_state: ChainState::empty(block_height, BlockHash([0; 32])),
            sapling_end_size: 0,
            orchard_end_size: 0,
            ironwood_end_size: 0,
        }
    }

    /// Produces metadata for a block as of the given chain state.
    pub fn at(
        chain_state: ChainState,
        sapling_end_size: u32,
        orchard_end_size: u32,
        ironwood_end_size: u32,
    ) -> Self {
        assert_eq!(
            chain_state.final_sapling_tree().tree_size() as u32,
            sapling_end_size
        );
        #[cfg(feature = "orchard")]
        assert_eq!(
            chain_state.final_orchard_tree().tree_size() as u32,
            orchard_end_size
        );
        #[cfg(feature = "orchard")]
        assert_eq!(
            chain_state.final_ironwood_tree().tree_size() as u32,
            ironwood_end_size
        );

        Self {
            chain_state,
            sapling_end_size,
            orchard_end_size,
            ironwood_end_size,
        }
    }

    fn roll_forward(&self, cb: &CompactBlock) -> Self {
        assert_eq!(self.chain_state.block_height() + 1, cb.height());

        let sapling_final_tree = cb.vtx.iter().flat_map(|tx| tx.outputs.iter()).fold(
            self.chain_state.final_sapling_tree().clone(),
            |mut acc, c_out| {
                acc.append(::sapling::Node::from_cmu(&c_out.cmu().unwrap()));
                acc
            },
        );
        let sapling_end_size = sapling_final_tree.tree_size() as u32;

        #[cfg(feature = "orchard")]
        let orchard_final_tree = cb.vtx.iter().flat_map(|tx| tx.actions.iter()).fold(
            self.chain_state.final_orchard_tree().clone(),
            |mut acc, c_act| {
                acc.append(MerkleHashOrchard::from_cmx(&c_act.cmx().unwrap()));
                acc
            },
        );
        #[cfg(feature = "orchard")]
        let orchard_end_size = orchard_final_tree.tree_size() as u32;
        #[cfg(not(feature = "orchard"))]
        let orchard_end_size = cb.vtx.iter().fold(self.orchard_end_size, |sz, tx| {
            sz + (tx.actions.len() as u32)
        });

        #[cfg(feature = "orchard")]
        let ironwood_final_tree = cb
            .vtx
            .iter()
            .flat_map(|tx| tx.ironwood_actions.iter())
            .fold(
                self.chain_state.final_ironwood_tree().clone(),
                |mut acc, c_act| {
                    acc.append(MerkleHashOrchard::from_cmx(&c_act.cmx().unwrap()));
                    acc
                },
            );
        #[cfg(feature = "orchard")]
        let ironwood_end_size = ironwood_final_tree.tree_size() as u32;
        #[cfg(not(feature = "orchard"))]
        let ironwood_end_size = cb.vtx.iter().fold(self.ironwood_end_size, |sz, tx| {
            sz + (tx.ironwood_actions.len() as u32)
        });

        Self {
            chain_state: ChainState::new(
                cb.height(),
                cb.hash(),
                sapling_final_tree,
                #[cfg(feature = "orchard")]
                orchard_final_tree,
                #[cfg(feature = "orchard")]
                ironwood_final_tree,
            ),
            sapling_end_size,
            orchard_end_size,
            ironwood_end_size,
        }
    }

    /// Returns the chain state as of the end of this block.
    pub fn chain_state(&self) -> &ChainState {
        &self.chain_state
    }

    /// Returns the height of this block.
    pub fn height(&self) -> BlockHeight {
        self.chain_state.block_height()
    }

    /// Returns the size of the Sapling note commitment tree as of the end of this block.
    pub fn sapling_end_size(&self) -> u32 {
        self.sapling_end_size
    }

    /// Returns the size of the Orchard note commitment tree as of the end of this block.
    pub fn orchard_end_size(&self) -> u32 {
        self.orchard_end_size
    }

    /// Returns the size of the Ironwood note commitment tree as of the end of this block.
    pub fn ironwood_end_size(&self) -> u32 {
        self.ironwood_end_size
    }
}

/// The test account configured for a [`TestState`].
///
/// Create this by calling either [`TestBuilder::with_account_from_sapling_activation`] or
/// [`TestBuilder::with_account_having_current_birthday`] while setting up a test, and
/// then access it with [`TestState::test_account`].
#[derive(Clone)]
pub struct TestAccount<A> {
    account: A,
    usk: UnifiedSpendingKey,
    birthday: AccountBirthday,
}

impl<A> TestAccount<A> {
    /// Returns the underlying wallet account.
    pub fn account(&self) -> &A {
        &self.account
    }

    /// Returns the account's unified spending key.
    pub fn usk(&self) -> &UnifiedSpendingKey {
        &self.usk
    }

    /// Returns the birthday that was configured for the account.
    pub fn birthday(&self) -> &AccountBirthday {
        &self.birthday
    }
}

impl<A: Account> Account for TestAccount<A> {
    type AccountId = A::AccountId;

    fn id(&self) -> Self::AccountId {
        self.account.id()
    }

    fn name(&self) -> Option<&str> {
        self.account.name()
    }

    fn birthday_height(&self) -> BlockHeight {
        self.account.birthday_height()
    }

    fn source(&self) -> &AccountSource {
        self.account.source()
    }

    fn ufvk(&self) -> Option<&zcash_keys::keys::UnifiedFullViewingKey> {
        self.account.ufvk()
    }

    fn uivk(&self) -> zcash_keys::keys::UnifiedIncomingViewingKey {
        self.account.uivk()
    }
}

/// Trait method exposing the ability to reset the wallet within a test.
// TODO: Does this need to exist separately from DataStoreFactory?
pub trait Reset: WalletTest + Sized {
    /// A handle that confers ownership of a specific wallet instance.
    type Handle;

    /// Replaces the wallet in `st` (via [`TestState::wallet_mut`]) with a new wallet
    /// database.
    ///
    /// This does not recreate accounts. The resulting wallet in `st` has no test account.
    ///
    /// Returns the old wallet.
    fn reset<C>(st: &mut TestState<C, Self, LocalNetwork>) -> Self::Handle;
}

/// The state for a `zcash_client_backend` test.
pub struct TestState<Cache, DataStore: WalletTest, Network> {
    cache: Cache,
    cached_blocks: BTreeMap<BlockHeight, CachedBlock>,
    latest_block_height: Option<BlockHeight>,
    wallet_data: DataStore,
    network: Network,
    test_account: Option<(SecretVec<u8>, TestAccount<DataStore::Account>)>,
    rng: TestRng,
}

impl<Cache, DataStore: WalletTest, Network> TestState<Cache, DataStore, Network> {
    /// Exposes an immutable reference to the test's `DataStore`.
    pub fn wallet(&self) -> &DataStore {
        &self.wallet_data
    }

    /// Exposes a mutable reference to the test's `DataStore`.
    pub fn wallet_mut(&mut self) -> &mut DataStore {
        &mut self.wallet_data
    }

    /// Exposes the test framework's source of randomness.
    pub fn rng_mut(&mut self) -> &mut TestRng {
        &mut self.rng
    }

    /// Exposes the network in use.
    pub fn network(&self) -> &Network {
        &self.network
    }
}

impl<Cache, DataStore: WalletTest, Network> Drop for TestState<Cache, DataStore, Network> {
    fn drop(&mut self) {
        self.wallet_data.finally();
    }
}

impl<Cache, DataStore: WalletTest, Network: consensus::Parameters>
    TestState<Cache, DataStore, Network>
{
    /// Convenience method for obtaining the Sapling activation height for the network under test.
    pub fn sapling_activation_height(&self) -> BlockHeight {
        self.network
            .activation_height(NetworkUpgrade::Sapling)
            .expect("Sapling activation height must be known.")
    }

    /// Convenience method for obtaining the NU5 activation height for the network under test.
    #[allow(dead_code)]
    pub fn nu5_activation_height(&self) -> BlockHeight {
        self.network
            .activation_height(NetworkUpgrade::Nu5)
            .expect("NU5 activation height must be known.")
    }

    /// Exposes the seed for the test wallet.
    pub fn test_seed(&self) -> Option<&SecretVec<u8>> {
        self.test_account.as_ref().map(|(seed, _)| seed)
    }

    /// Returns a reference to the test account, if one was configured.
    pub fn test_account(&self) -> Option<&TestAccount<<DataStore as WalletRead>::Account>> {
        self.test_account.as_ref().map(|(_, acct)| acct)
    }

    /// Returns the test account's Sapling DFVK, if one was configured.
    pub fn test_account_sapling(&self) -> Option<&DiversifiableFullViewingKey> {
        let (_, acct) = self.test_account.as_ref()?;
        let ufvk = acct.ufvk()?;
        ufvk.sapling()
    }

    /// Returns the test account's Orchard FVK, if one was configured.
    #[cfg(feature = "orchard")]
    pub fn test_account_orchard(&self) -> Option<&::orchard::keys::FullViewingKey> {
        let (_, acct) = self.test_account.as_ref()?;
        let ufvk = acct.ufvk()?;
        ufvk.orchard()
    }
}

impl<Cache, DataStore, Network> TestState<Cache, DataStore, Network>
where
    DataStore: WalletTest + WalletWrite,
    Network: consensus::Parameters,
{
    /// Creates a FURTHER account under the test seed, at the test account's birthday, and returns
    /// its id and spending key.
    ///
    /// The wallet assigns the next unused ZIP 32 account index, so this is a sibling of the
    /// account [`TestBuilder`] configured — the shape a test needs to check that some answer is
    /// scoped to the account it was asked of, rather than to the wallet.
    ///
    /// Create every account a test needs BEFORE scanning anything: account creation adjusts the
    /// scan queue, which clears the wallet's fully-scanned height.
    pub fn create_account_from_test_seed(
        &mut self,
        account_name: &str,
    ) -> (<DataStore as WalletRead>::AccountId, UnifiedSpendingKey) {
        let seed = SecretVec::new(
            self.test_seed()
                .expect("the test state was built with a seed")
                .expose_secret()
                .clone(),
        );
        let birthday = self
            .test_account()
            .expect("the test state was built with an account")
            .birthday()
            .clone();
        self.wallet_mut()
            .create_account(account_name, &seed, &birthday, None)
            .expect("creates a further account under the test seed")
    }
}

impl<Cache: TestCache, DataStore, Network> TestState<Cache, DataStore, Network>
where
    Network: consensus::Parameters,
    DataStore: WalletTest + WalletWrite,
    <Cache::BlockSource as BlockSource>::Error: fmt::Debug,
{
    /// Exposes an immutable reference to the test's [`BlockSource`].
    #[cfg(feature = "unstable")]
    pub fn cache(&self) -> &Cache::BlockSource {
        self.cache.block_source()
    }

    /// Returns the cached chain state corresponding to the latest block generated by this
    /// `TestState`.
    pub fn latest_cached_block(&self) -> Option<&CachedBlock> {
        self.latest_block_height
            .as_ref()
            .and_then(|h| self.cached_blocks.get(h))
    }

    fn latest_cached_block_below_height(&self, height: BlockHeight) -> Option<&CachedBlock> {
        self.cached_blocks.range(..height).last().map(|(_, b)| b)
    }

    fn cache_block(
        &mut self,
        prev_block: &CachedBlock,
        compact_block: CompactBlock,
    ) -> Cache::InsertResult {
        self.cached_blocks.insert(
            compact_block.height(),
            prev_block.roll_forward(&compact_block),
        );
        self.cache.insert(&compact_block)
    }

    /// Creates a fake block at the expected next height containing a single output of the
    /// given value, and inserts it into the cache.
    ///
    /// This is a proxy for `generate_next_block_multi`.
    pub fn generate_next_block<Fvk: TestFvk>(
        &mut self,
        recipient_fvk: &Fvk,
        recipient_address_type: AddressType,
        value: Zatoshis,
    ) -> (BlockHeight, Cache::InsertResult, Fvk::Nullifier) {
        let (height, res, nfs) = self.generate_next_block_multi(&[FakeCompactOutput::new(
            recipient_fvk,
            recipient_address_type,
            value,
        )]);

        (height, res, nfs[0])
    }

    /// Creates a fake block at the expected next height containing multiple outputs
    /// and inserts it into the cache.
    pub fn generate_next_block_multi<Fvk: TestFvk>(
        &mut self,
        outputs: &[FakeCompactOutput<Fvk>],
    ) -> (BlockHeight, Cache::InsertResult, Vec<Fvk::Nullifier>) {
        let pre_activation_block = CachedBlock::none(self.sapling_activation_height() - 1);
        let prior_cached_block = self.latest_cached_block().unwrap_or(&pre_activation_block);
        let height = prior_cached_block.height() + 1;

        let (res, nfs) = self.generate_block_at(
            height,
            prior_cached_block.chain_state.block_hash(),
            outputs,
            prior_cached_block.sapling_end_size,
            prior_cached_block.orchard_end_size,
            prior_cached_block.ironwood_end_size,
            false,
        );

        (height, res, nfs)
    }

    /// Adds an empty block to the cache, advancing the simulated chain height.
    pub fn generate_empty_block(&mut self) -> (BlockHeight, Cache::InsertResult) {
        let new_hash = {
            let mut hash = vec![0; 32];
            self.rng.fill_bytes(&mut hash);
            hash
        };

        let pre_activation_block = CachedBlock::none(self.sapling_activation_height() - 1);
        let prior_cached_block = self
            .latest_cached_block()
            .unwrap_or(&pre_activation_block)
            .clone();
        let new_height = prior_cached_block.height() + 1;

        let mut cb = CompactBlock {
            hash: new_hash,
            height: new_height.into(),
            ..Default::default()
        };
        cb.prev_hash
            .extend_from_slice(&prior_cached_block.chain_state.block_hash().0);

        cb.chain_metadata = Some(compact_formats::ChainMetadata {
            sapling_commitment_tree_size: prior_cached_block.sapling_end_size,
            orchard_commitment_tree_size: prior_cached_block.orchard_end_size,
            ironwood_commitment_tree_size: prior_cached_block.ironwood_end_size,
        });

        let res = self.cache_block(&prior_cached_block, cb);
        self.latest_block_height = Some(new_height);

        (new_height, res)
    }

    /// Creates a fake block with the given height and hash containing the requested outputs, and
    /// inserts it into the cache.
    ///
    /// This generated block will be treated as the latest block, and subsequent calls to
    /// [`Self::generate_next_block`] will build on it.
    #[allow(clippy::too_many_arguments)]
    pub fn generate_block_at<Fvk: TestFvk>(
        &mut self,
        height: BlockHeight,
        prev_hash: BlockHash,
        outputs: &[FakeCompactOutput<Fvk>],
        initial_sapling_tree_size: u32,
        initial_orchard_tree_size: u32,
        initial_ironwood_tree_size: u32,
        allow_broken_hash_chain: bool,
    ) -> (Cache::InsertResult, Vec<Fvk::Nullifier>) {
        let mut prior_cached_block = self
            .latest_cached_block_below_height(height)
            .cloned()
            .unwrap_or_else(|| CachedBlock::none(self.sapling_activation_height() - 1));
        assert!(prior_cached_block.chain_state.block_height() < height);
        assert!(prior_cached_block.sapling_end_size <= initial_sapling_tree_size);
        assert!(prior_cached_block.orchard_end_size <= initial_orchard_tree_size);
        assert!(prior_cached_block.ironwood_end_size <= initial_ironwood_tree_size);

        // If the block height has increased or the Sapling and/or Orchard tree sizes have changed,
        // we need to generate a new prior cached block that the block to be generated can
        // successfully chain from, with the provided tree sizes.
        if prior_cached_block.chain_state.block_height() == height - 1 {
            if !allow_broken_hash_chain {
                assert_eq!(prev_hash, prior_cached_block.chain_state.block_hash());
            }
        } else {
            let final_sapling_tree =
                (prior_cached_block.sapling_end_size..initial_sapling_tree_size).fold(
                    prior_cached_block.chain_state.final_sapling_tree().clone(),
                    |mut acc, _| {
                        acc.append(::sapling::Node::from_scalar(bls12_381::Scalar::random(
                            &mut self.rng,
                        )));
                        acc
                    },
                );

            #[cfg(feature = "orchard")]
            let final_orchard_tree =
                (prior_cached_block.orchard_end_size..initial_orchard_tree_size).fold(
                    prior_cached_block.chain_state.final_orchard_tree().clone(),
                    |mut acc, _| {
                        acc.append(MerkleHashOrchard::random(&mut self.rng));
                        acc
                    },
                );

            #[cfg(feature = "orchard")]
            let final_ironwood_tree =
                (prior_cached_block.ironwood_end_size..initial_ironwood_tree_size).fold(
                    prior_cached_block.chain_state.final_ironwood_tree().clone(),
                    |mut acc, _| {
                        acc.append(MerkleHashOrchard::random(&mut self.rng));
                        acc
                    },
                );

            prior_cached_block = CachedBlock::at(
                ChainState::new(
                    height - 1,
                    prev_hash,
                    final_sapling_tree,
                    #[cfg(feature = "orchard")]
                    final_orchard_tree,
                    #[cfg(feature = "orchard")]
                    final_ironwood_tree,
                ),
                initial_sapling_tree_size,
                initial_orchard_tree_size,
                initial_ironwood_tree_size,
            );

            self.cached_blocks
                .insert(height - 1, prior_cached_block.clone());
        }

        let (cb, nfs) = fake_compact_block(
            &self.network,
            height,
            prev_hash,
            None,
            outputs,
            initial_sapling_tree_size,
            initial_orchard_tree_size,
            initial_ironwood_tree_size,
            &mut self.rng,
        );
        assert_eq!(cb.height(), height);

        let res = self.cache_block(&prior_cached_block, cb);
        self.latest_block_height = Some(height);

        (res, nfs)
    }

    /// Creates a fake block at the expected next height spending the given note, and
    /// inserts it into the cache.
    pub fn generate_next_block_spending<Fvk: TestFvk>(
        &mut self,
        sender_fvk: &Fvk,
        note: (Fvk::Nullifier, Zatoshis),
        to: impl Into<Address>,
        value: Zatoshis,
    ) -> (BlockHeight, Cache::InsertResult) {
        let prior_cached_block = self
            .latest_cached_block()
            .cloned()
            .unwrap_or_else(|| CachedBlock::none(self.sapling_activation_height() - 1));
        let height = prior_cached_block.height() + 1;

        let cb = fake_compact_block_spending(
            &self.network,
            height,
            prior_cached_block.chain_state.block_hash(),
            note,
            sender_fvk,
            to.into(),
            value,
            prior_cached_block.sapling_end_size,
            prior_cached_block.orchard_end_size,
            prior_cached_block.ironwood_end_size,
            &mut self.rng,
        );
        assert_eq!(cb.height(), height);

        let res = self.cache_block(&prior_cached_block, cb);
        self.latest_block_height = Some(height);

        (height, res)
    }

    /// Creates a fake block at the expected next height containing only the wallet
    /// transaction with the given txid, and inserts it into the cache.
    ///
    /// This generated block will be treated as the latest block, and subsequent calls to
    /// [`Self::generate_next_block`] (or similar) will build on it.
    pub fn generate_next_block_including(
        &mut self,
        txid: TxId,
    ) -> (BlockHeight, Cache::InsertResult) {
        let tx = self
            .wallet()
            .get_transaction(txid)
            .unwrap()
            .expect("TxId should exist in the wallet");

        // Index 0 is by definition a coinbase transaction, and the wallet doesn't
        // construct coinbase transactions. So we pretend here that the block has a
        // coinbase transaction that does not have shielded coinbase outputs.
        self.generate_next_block_from_tx(1, &tx)
    }

    /// Creates a fake block at the expected next height containing only the given
    /// transaction, and inserts it into the cache.
    ///
    /// This generated block will be treated as the latest block, and subsequent calls to
    /// [`Self::generate_next_block`] will build on it.
    pub fn generate_next_block_from_tx(
        &mut self,
        tx_index: usize,
        tx: &Transaction,
    ) -> (BlockHeight, Cache::InsertResult) {
        let prior_cached_block = self
            .latest_cached_block()
            .cloned()
            .unwrap_or_else(|| CachedBlock::none(self.sapling_activation_height() - 1));
        let height = prior_cached_block.height() + 1;

        let cb = fake_compact_block_from_tx(
            height,
            prior_cached_block.chain_state.block_hash(),
            tx_index,
            tx,
            prior_cached_block.sapling_end_size,
            prior_cached_block.orchard_end_size,
            prior_cached_block.ironwood_end_size,
            &mut self.rng,
        );
        assert_eq!(cb.height(), height);

        let res = self.cache_block(&prior_cached_block, cb);
        self.latest_block_height = Some(height);

        (height, res)
    }

    /// Truncates the test wallet and block cache to the specified height, discarding all data from
    /// blocks at heights greater than the specified height, excluding transaction data that may
    /// not be recoverable from the chain.
    pub fn truncate_to_height(&mut self, height: BlockHeight) {
        self.wallet_mut().truncate_to_height(height).unwrap();
        self.cache.truncate_to_height(height);
        self.cached_blocks.split_off(&(height + 1));
        self.latest_block_height = Some(height);
    }

    /// Truncates the test wallet to the specified height, and resets the cache's latest block
    /// height but does not truncate the block cache. This is useful for circumstances when you
    /// want to re-scan a set of cached blocks.
    pub fn truncate_to_height_retaining_cache(&mut self, height: BlockHeight) {
        self.wallet_mut().truncate_to_height(height).unwrap();
        self.latest_block_height = Some(height);
    }
}

impl<Cache, DbT, ParamsT> TestState<Cache, DbT, ParamsT>
where
    Cache: TestCache,
    <Cache::BlockSource as BlockSource>::Error: fmt::Debug,
    ParamsT: consensus::Parameters + Send + 'static,
    DbT: InputSource + WalletTest + WalletWrite + WalletCommitmentTrees,
    <DbT as WalletRead>::AccountId:
        std::fmt::Debug + ConditionallySelectable + Default + Send + Sync + 'static,
{
    /// Invokes [`scan_cached_blocks`] with the given arguments, expecting success.
    pub fn scan_cached_blocks(&mut self, from_height: BlockHeight, limit: usize) -> ScanSummary {
        let result = self.try_scan_cached_blocks(from_height, limit);
        assert_matches!(result, Ok(_));
        result.unwrap()
    }

    /// Invokes [`scan_cached_blocks`] with the given arguments.
    pub fn try_scan_cached_blocks(
        &mut self,
        from_height: BlockHeight,
        limit: usize,
    ) -> Result<
        ScanSummary,
        super::chain::error::Error<
            <DbT as WalletRead>::Error,
            <Cache::BlockSource as BlockSource>::Error,
        >,
    > {
        let prior_cached_block = self
            .latest_cached_block_below_height(from_height)
            .cloned()
            .unwrap_or_else(|| CachedBlock::none(from_height - 1));

        scan_cached_blocks(
            &self.network,
            self.cache.block_source(),
            &mut self.wallet_data,
            from_height,
            &prior_cached_block.chain_state,
            limit,
        )
    }

    /// Invokes [`scan_cached_blocks`] with a caller-supplied `from_state` instead of deriving it
    /// from the block cache.
    ///
    /// This is primarily useful for tests that need to drive [`WalletWrite::put_blocks`] with a
    /// `from_state` that is deliberately inconsistent with the wallet's stored note commitment
    /// tree state, in order to exercise the resulting error paths.
    pub fn try_scan_cached_blocks_with_state(
        &mut self,
        from_height: BlockHeight,
        from_state: &ChainState,
        limit: usize,
    ) -> Result<
        ScanSummary,
        super::chain::error::Error<
            <DbT as WalletRead>::Error,
            <Cache::BlockSource as BlockSource>::Error,
        >,
    > {
        scan_cached_blocks(
            &self.network,
            self.cache.block_source(),
            &mut self.wallet_data,
            from_height,
            from_state,
            limit,
        )
    }

    /// Insert shard roots for both trees.
    pub fn put_subtree_roots(
        &mut self,
        sapling_start_index: u64,
        sapling_roots: &[CommitmentTreeRoot<::sapling::Node>],
        #[cfg(feature = "orchard")] orchard_start_index: u64,
        #[cfg(feature = "orchard")] orchard_roots: &[CommitmentTreeRoot<MerkleHashOrchard>],
    ) -> Result<(), ShardTreeError<<DbT as WalletCommitmentTrees>::Error>> {
        self.wallet_mut()
            .put_sapling_subtree_roots(sapling_start_index, sapling_roots)?;

        #[cfg(feature = "orchard")]
        self.wallet_mut()
            .put_orchard_subtree_roots(orchard_start_index, orchard_roots)?;

        Ok(())
    }

    /// Generates `n` empty blocks, scans each, and returns the wallet's resulting fully-scanned
    /// height.
    ///
    /// This is the "let the chain advance" step of a test that needs the scanned region to reach a
    /// chosen depth above some earlier height — an anchor boundary a fixed number of blocks below
    /// the tip, say — with none of the intervening blocks carrying wallet-relevant data.
    pub fn generate_and_scan_empty_blocks(&mut self, n: usize) -> BlockHeight {
        for _ in 0..n {
            let (height, _) = self.generate_empty_block();
            self.scan_cached_blocks(height, 1);
        }
        self.wallet()
            .block_fully_scanned()
            .expect("the wallet reports its fully-scanned block")
            .expect("the wallet is fully scanned")
            .block_height()
    }

    /// The root of the wallet's own Orchard note commitment tree at the checkpoint `height`, as an
    /// anchor: the value a transaction proved against that height would have installed.
    ///
    /// `None` when the tree holds no checkpoint there; the tree's own error when it holds one but
    /// cannot complete a root over the shard data it retains.
    #[cfg(feature = "orchard")]
    pub fn orchard_anchor_at(
        &mut self,
        height: BlockHeight,
    ) -> Result<Option<::orchard::Anchor>, ShardTreeError<<DbT as WalletCommitmentTrees>::Error>>
    {
        self.wallet_mut()
            .with_orchard_tree_mut(|tree| tree.root_at_checkpoint_id(&height))
            .map(|root| root.map(::orchard::Anchor::from))
    }
}

impl<Cache, DbT, ParamsT, AccountIdT, ErrT> TestState<Cache, DbT, ParamsT>
where
    ParamsT: consensus::Parameters + Send + 'static,
    AccountIdT: std::fmt::Debug + std::cmp::Eq + std::hash::Hash,
    ErrT: std::fmt::Debug,
    DbT: InputSource<AccountId = AccountIdT, Error = ErrT>
        + WalletTest
        + WalletRead<AccountId = AccountIdT, Error = ErrT>
        + WalletWrite
        + WalletCommitmentTrees,
    <DbT as WalletRead>::AccountId: ConditionallySelectable + Default + Send + 'static,
{
    // Creates a transaction that sends the specified value from the given account to
    // the provided recipient address, using a greedy input selector and the default
    // mutli-output change strategy.
    pub fn create_standard_transaction(
        &mut self,
        from_account: &TestAccount<DbT::Account>,
        to: ZcashAddress,
        value: Zatoshis,
    ) -> Result<
        NonEmpty<TxId>,
        super::wallet::TransferErrT<
            DbT,
            GreedyInputSelector<DbT>,
            standard::MultiOutputChangeStrategy<DbT>,
        >,
    > {
        let input_selector = GreedyInputSelector::new();

        #[cfg(not(feature = "orchard"))]
        let fallback_change_pool = ShieldedPool::Sapling;
        #[cfg(feature = "orchard")]
        let fallback_change_pool = ShieldedPool::Orchard;

        let change_strategy =
            single_output_change_strategy(StandardFeeRule::Zip317, None, fallback_change_pool);

        let request =
            zip321::TransactionRequest::new(vec![Payment::without_memo(to, value)]).unwrap();

        self.spend(
            &input_selector,
            &change_strategy,
            from_account.usk(),
            request,
            OvkPolicy::Sender,
            ConfirmationsPolicy::MIN,
        )
    }

    /// Prepares and executes the given [`zip321::TransactionRequest`] in a single step.
    #[allow(clippy::type_complexity)]
    pub fn spend<InputsT, ChangeT>(
        &mut self,
        input_selector: &InputsT,
        change_strategy: &ChangeT,
        usk: &UnifiedSpendingKey,
        request: zip321::TransactionRequest,
        ovk_policy: OvkPolicy,
        confirmations_policy: ConfirmationsPolicy,
    ) -> Result<NonEmpty<TxId>, super::wallet::TransferErrT<DbT, InputsT, ChangeT>>
    where
        InputsT: InputSelector<InputSource = DbT>,
        ChangeT: ChangeStrategy<MetaSource = DbT>,
    {
        let network = self.network().clone();

        let account = self
            .wallet()
            .get_account_for_ufvk(&usk.to_unified_full_viewing_key())
            .map_err(Error::DataSource)?
            .ok_or(Error::KeyNotRecognized)?;

        let proposal = propose_transfer(
            self.wallet_mut(),
            &network,
            account.id(),
            input_selector,
            change_strategy,
            request,
            confirmations_policy,
            &SpendPolicy::default(),
            None,
            None,
        )?;

        create_proposed_transactions(
            self.wallet_mut(),
            &network,
            &MockSpendProver,
            &MockOutputProver,
            &SpendingKeys::from_unified_spending_key(usk.clone()),
            ovk_policy,
            &proposal,
            None,
        )
    }

    /// Invokes [`propose_transfer`] with the given arguments.
    #[allow(clippy::type_complexity)]
    pub fn propose_transfer<InputsT, ChangeT>(
        &mut self,
        spend_from_account: <DbT as InputSource>::AccountId,
        input_selector: &InputsT,
        change_strategy: &ChangeT,
        request: zip321::TransactionRequest,
        confirmations_policy: ConfirmationsPolicy,
    ) -> Result<
        Proposal<ChangeT::FeeRule, <DbT as InputSource>::NoteRef>,
        super::wallet::ProposeTransferErrT<DbT, Infallible, InputsT, ChangeT>,
    >
    where
        InputsT: InputSelector<InputSource = DbT>,
        ChangeT: ChangeStrategy<MetaSource = DbT>,
    {
        let network = self.network().clone();
        propose_transfer::<_, _, _, _, Infallible>(
            self.wallet_mut(),
            &network,
            spend_from_account,
            input_selector,
            change_strategy,
            request,
            confirmations_policy,
            &SpendPolicy::default(),
            None,
            None,
        )
    }

    /// Invokes [`propose_transfer`] with the given arguments and an explicit
    /// [`SpendPolicy`].
    ///
    /// Unlike [`Self::propose_transfer`], which always uses the default spend
    /// policy (every shielded pool, no transparent), this allows tests to opt in
    /// to spending the account's transparent UTXOs or to restrict the shielded
    /// pools notes may be drawn from.
    #[allow(clippy::type_complexity)]
    pub fn propose_transfer_with_policy<InputsT, ChangeT>(
        &mut self,
        spend_from_account: <DbT as InputSource>::AccountId,
        input_selector: &InputsT,
        change_strategy: &ChangeT,
        request: zip321::TransactionRequest,
        confirmations_policy: ConfirmationsPolicy,
        spend_policy: &SpendPolicy,
    ) -> Result<
        Proposal<ChangeT::FeeRule, <DbT as InputSource>::NoteRef>,
        super::wallet::ProposeTransferErrT<DbT, Infallible, InputsT, ChangeT>,
    >
    where
        InputsT: InputSelector<InputSource = DbT>,
        ChangeT: ChangeStrategy<MetaSource = DbT>,
    {
        let network = self.network().clone();
        propose_transfer::<_, _, _, _, Infallible>(
            self.wallet_mut(),
            &network,
            spend_from_account,
            input_selector,
            change_strategy,
            request,
            confirmations_policy,
            spend_policy,
            None,
            None,
        )
    }

    /// Invokes [`propose_transfer`] with the given arguments.
    #[allow(clippy::type_complexity)]
    pub fn propose_send_max_transfer<FeeRuleT>(
        &mut self,
        spend_from_account: <DbT as InputSource>::AccountId,
        fee_rule: &FeeRuleT,
        to: ZcashAddress,
        memo: Option<MemoBytes>,
        mode: MaxSpendMode,
        confirmations_policy: ConfirmationsPolicy,
    ) -> Result<
        Proposal<FeeRuleT, <DbT as InputSource>::NoteRef>,
        super::wallet::ProposeSendMaxErrT<DbT, Infallible, FeeRuleT>,
    >
    where
        FeeRuleT: FeeRule + Clone,
    {
        let network = self.network().clone();
        propose_send_max_transfer::<_, _, _, Infallible>(
            self.wallet_mut(),
            &network,
            spend_from_account,
            &[ShieldedPool::Sapling, ShieldedPool::Orchard],
            fee_rule,
            to,
            memo,
            mode,
            confirmations_policy,
            &LockedInputPolicy::Exclude,
            None,
        )
    }

    /// Invokes [`propose_standard_transfer_to_address`] with the given arguments.
    #[allow(clippy::type_complexity)]
    #[allow(clippy::too_many_arguments)]
    pub fn propose_standard_transfer<CommitmentTreeErrT>(
        &mut self,
        spend_from_account: <DbT as InputSource>::AccountId,
        fee_rule: StandardFeeRule,
        confirmations_policy: ConfirmationsPolicy,
        to: &Address,
        amount: Zatoshis,
        memo: Option<MemoBytes>,
        change_memo: Option<MemoBytes>,
        fallback_change_pool: ShieldedPool,
    ) -> Result<
        Proposal<StandardFeeRule, <DbT as InputSource>::NoteRef>,
        super::wallet::ProposeTransferErrT<
            DbT,
            CommitmentTreeErrT,
            GreedyInputSelector<DbT>,
            SingleOutputChangeStrategy<DbT>,
        >,
    > {
        let network = self.network().clone();
        let result = propose_standard_transfer_to_address::<_, _, CommitmentTreeErrT>(
            self.wallet_mut(),
            &network,
            fee_rule,
            spend_from_account,
            confirmations_policy,
            to,
            amount,
            memo,
            change_memo,
            fallback_change_pool,
            None,
            None,
        );

        if let Ok(proposal) = &result {
            check_proposal_serialization_roundtrip(&network, self.wallet(), proposal);
        }

        result
    }

    /// Invokes [`propose_shielding`] with the given arguments.
    ///
    /// [`propose_shielding`]: crate::data_api::wallet::propose_shielding
    #[cfg(feature = "transparent-inputs")]
    #[allow(clippy::type_complexity)]
    #[allow(clippy::too_many_arguments)]
    #[allow(dead_code)]
    pub fn propose_shielding<InputsT, ChangeT>(
        &mut self,
        input_selector: &InputsT,
        change_strategy: &ChangeT,
        shielding_threshold: Zatoshis,
        from_addrs: &[TransparentAddress],
        to_account: <InputsT::InputSource as InputSource>::AccountId,
        confirmations_policy: ConfirmationsPolicy,
        output_filter: CoinbaseFilter,
    ) -> Result<
        Proposal<ChangeT::FeeRule, Infallible>,
        super::wallet::ProposeShieldingErrT<DbT, Infallible, InputsT, ChangeT>,
    >
    where
        InputsT: ShieldingSelector<InputSource = DbT>,
        ChangeT: ChangeStrategy<MetaSource = DbT>,
    {
        let network = self.network().clone();
        propose_shielding::<_, _, _, _, Infallible>(
            self.wallet_mut(),
            &network,
            input_selector,
            change_strategy,
            shielding_threshold,
            from_addrs,
            to_account,
            confirmations_policy,
            output_filter,
            None,
        )
    }

    /// Invokes [`propose_shielding_coinbase`] with the given arguments.
    ///
    /// [`propose_shielding_coinbase`]: crate::data_api::wallet::propose_shielding_coinbase
    #[cfg(feature = "transparent-inputs")]
    #[allow(clippy::type_complexity)]
    #[allow(clippy::too_many_arguments)]
    #[allow(dead_code)]
    pub fn propose_shielding_coinbase<InputsT, FeeRuleT>(
        &mut self,
        input_selector: &InputsT,
        fee_rule: &FeeRuleT,
        shielding_threshold: Zatoshis,
        from_addrs: &[TransparentAddress],
        to_address: zcash_address::ZcashAddress,
        memo: Option<zcash_protocol::memo::MemoBytes>,
        limit: Option<usize>,
    ) -> Result<
        Proposal<FeeRuleT, Infallible>,
        super::wallet::ProposeShieldingCoinbaseErrT<DbT, Infallible, InputsT, FeeRuleT>,
    >
    where
        InputsT: ShieldingSelector<InputSource = DbT>,
        FeeRuleT: zcash_primitives::transaction::fees::FeeRule + Clone,
    {
        let network = self.network().clone();
        propose_shielding_coinbase::<_, _, _, _, Infallible>(
            self.wallet_mut(),
            &network,
            input_selector,
            fee_rule,
            shielding_threshold,
            from_addrs,
            to_address,
            memo,
            limit,
            None,
        )
    }

    /// Invokes [`create_proposed_transactions`] with the given arguments.
    #[allow(clippy::type_complexity)]
    pub fn create_proposed_transactions<InputsErrT, FeeRuleT, ChangeErrT, N>(
        &mut self,
        usk: &UnifiedSpendingKey,
        ovk_policy: OvkPolicy,
        proposal: &Proposal<FeeRuleT, N>,
    ) -> Result<NonEmpty<TxId>, super::wallet::CreateErrT<DbT, InputsErrT, FeeRuleT, ChangeErrT, N>>
    where
        FeeRuleT: FeeRule,
    {
        let network = self.network().clone();
        create_proposed_transactions(
            self.wallet_mut(),
            &network,
            &MockSpendProver,
            &MockOutputProver,
            &SpendingKeys::from_unified_spending_key(usk.clone()),
            ovk_policy,
            proposal,
            None,
        )
    }

    /// Invokes [`create_pczt_from_proposal`] with the given arguments.
    ///
    /// [`create_pczt_from_proposal`]: super::wallet::create_pczt_from_proposal
    #[cfg(feature = "pczt")]
    #[allow(clippy::type_complexity)]
    pub fn create_pczt_from_proposal<InputsErrT, FeeRuleT, ChangeErrT>(
        &mut self,
        spend_from_account: <DbT as InputSource>::AccountId,
        ovk_policy: OvkPolicy,
        proposal: &Proposal<FeeRuleT, <DbT as InputSource>::NoteRef>,
        expiry_height: Option<BlockHeight>,
    ) -> Result<
        pczt::Pczt,
        super::wallet::CreateErrT<DbT, InputsErrT, FeeRuleT, ChangeErrT, DbT::NoteRef>,
    >
    where
        <DbT as WalletRead>::AccountId: serde::Serialize,
        FeeRuleT: FeeRule,
    {
        let network = self.network().clone();

        create_pczt_from_proposal(
            self.wallet_mut(),
            &network,
            spend_from_account,
            ovk_policy,
            proposal,
            expiry_height,
            ::zcash_primitives::transaction::builder::BundlePadding::DEFAULT,
        )
    }

    /// Invokes [`extract_and_store_transaction_from_pczt`] with the given arguments.
    ///
    /// [`extract_and_store_transaction_from_pczt`]: super::wallet::extract_and_store_transaction_from_pczt
    #[cfg(feature = "pczt")]
    #[allow(clippy::type_complexity)]
    pub fn extract_and_store_transaction_from_pczt(
        &mut self,
        pczt: pczt::Pczt,
    ) -> Result<TxId, super::wallet::ExtractErrT<DbT, DbT::NoteRef>>
    where
        <DbT as WalletRead>::AccountId: serde::de::DeserializeOwned,
    {
        let prover = real_test_prover();
        let (spend_vk, output_vk) = prover.verifying_keys();

        extract_and_store_transaction_from_pczt(
            self.wallet_mut(),
            pczt,
            Some((&spend_vk, &output_vk)),
            None,
        )
    }

    /// Invokes [`shield_transparent_funds`] with the given arguments.
    ///
    /// [`shield_transparent_funds`]: crate::data_api::wallet::shield_transparent_funds
    #[cfg(feature = "transparent-inputs")]
    #[allow(clippy::type_complexity)]
    #[allow(clippy::too_many_arguments)]
    pub fn shield_transparent_funds<InputsT, ChangeT>(
        &mut self,
        input_selector: &InputsT,
        change_strategy: &ChangeT,
        shielding_threshold: Zatoshis,
        usk: &UnifiedSpendingKey,
        from_addrs: &[TransparentAddress],
        to_account: <DbT as InputSource>::AccountId,
        confirmations_policy: ConfirmationsPolicy,
    ) -> Result<NonEmpty<TxId>, super::wallet::ShieldErrT<DbT, InputsT, ChangeT>>
    where
        InputsT: ShieldingSelector<InputSource = DbT>,
        ChangeT: ChangeStrategy<MetaSource = DbT>,
    {
        let network = self.network().clone();
        shield_transparent_funds(
            self.wallet_mut(),
            &network,
            &MockSpendProver,
            &MockOutputProver,
            input_selector,
            change_strategy,
            shielding_threshold,
            &SpendingKeys::from_unified_spending_key(usk.clone()),
            from_addrs,
            to_account,
            confirmations_policy,
        )
    }

    fn with_account_balance<T, F: FnOnce(&AccountBalance) -> T>(
        &self,
        account: AccountIdT,
        confirmations_policy: ConfirmationsPolicy,
        f: F,
    ) -> T {
        let binding = self
            .wallet()
            .get_wallet_summary(confirmations_policy)
            .unwrap()
            .unwrap();
        f(binding.account_balances().get(&account).unwrap())
    }

    /// Returns the total balance in the given account at this point in the test.
    pub fn get_total_balance(&self, account: AccountIdT) -> Zatoshis {
        self.with_account_balance(account, ConfirmationsPolicy::MIN, |balance| balance.total())
    }

    /// Returns the locked balance in the given account at this point in the test.
    pub fn get_locked_balance(&self, account: AccountIdT) -> Zatoshis {
        self.with_account_balance(account, ConfirmationsPolicy::MIN, |balance| {
            balance.locked_value()
        })
    }

    /// Returns the balance in the given account that is spendable with the given number
    /// of confirmations at this point in the test.
    pub fn get_spendable_balance(
        &self,
        account: AccountIdT,
        confirmations_policy: ConfirmationsPolicy,
    ) -> Zatoshis {
        self.with_account_balance(account, confirmations_policy, |balance| {
            balance.spendable_value()
        })
    }

    /// Returns the balance in the given account that is detected but not yet spendable
    /// with the given number of confirmations at this point in the test.
    pub fn get_pending_shielded_balance(
        &self,
        account: AccountIdT,
        confirmations_policy: ConfirmationsPolicy,
    ) -> Zatoshis {
        self.with_account_balance(account, confirmations_policy, |balance| {
            balance.value_pending_spendability() + balance.change_pending_confirmation()
        })
        .unwrap()
    }

    /// Returns the amount of change in the given account that is not yet spendable with
    /// the given number of confirmations at this point in the test.
    #[allow(dead_code)]
    pub fn get_pending_change(
        &self,
        account: AccountIdT,
        confirmations_policy: ConfirmationsPolicy,
    ) -> Zatoshis {
        self.with_account_balance(account, confirmations_policy, |balance| {
            balance.change_pending_confirmation()
        })
    }

    /// Returns a summary of the wallet at this point in the test.
    pub fn get_wallet_summary(
        &self,
        confirmations_policy: ConfirmationsPolicy,
    ) -> Option<WalletSummary<AccountIdT>> {
        self.wallet()
            .get_wallet_summary(confirmations_policy)
            .unwrap()
    }
}

impl<Cache, DbT, ParamsT, AccountIdT, ErrT> TestState<Cache, DbT, ParamsT>
where
    ParamsT: consensus::Parameters + Send + 'static,
    AccountIdT: std::cmp::Eq + std::hash::Hash,
    ErrT: std::fmt::Debug,
    DbT: InputSource<AccountId = AccountIdT, Error = ErrT>
        + WalletTest
        + WalletRead<AccountId = AccountIdT, Error = ErrT>
        + WalletWrite
        + WalletCommitmentTrees,
    <DbT as WalletRead>::AccountId: ConditionallySelectable + Default + Send + 'static,
{
    /// Returns a transaction from the history.
    #[allow(dead_code)]
    pub fn get_tx_from_history(
        &self,
        txid: TxId,
    ) -> Result<Option<TransactionSummary<AccountIdT>>, ErrT> {
        let history = self.wallet().get_tx_history()?;
        Ok(history.into_iter().find(|tx| tx.txid() == txid))
    }
}

impl<Cache, DbT: WalletRead + Reset> TestState<Cache, DbT, LocalNetwork> {
    /// Resets the wallet using a new wallet database but with the same cache of blocks,
    /// and returns the old wallet database file.
    ///
    /// This does not recreate accounts, nor does it rescan the cached blocks.
    /// The resulting wallet has no test account.
    /// Before using any `generate_*` method on the reset state, call `reset_latest_cached_block()`.
    pub fn reset(&mut self) -> DbT::Handle {
        self.latest_block_height = None;
        self.test_account = None;
        DbT::reset(self)
    }

    //    /// Reset the latest cached block to the most recent one in the cache database.
    //    #[allow(dead_code)]
    //    pub fn reset_latest_cached_block(&mut self) {
    //        self.cache
    //            .block_source()
    //            .with_blocks::<_, Infallible>(None, None, |block: CompactBlock| {
    //                let chain_metadata = block.chain_metadata.unwrap();
    //                self.latest_cached_block = Some(CachedBlock::at(
    //                    BlockHash::from_slice(block.hash.as_slice()),
    //                    BlockHeight::from_u32(block.height.try_into().unwrap()),
    //                    chain_metadata.sapling_commitment_tree_size,
    //                    chain_metadata.orchard_commitment_tree_size,
    //                ));
    //                Ok(())
    //            })
    //            .unwrap();
    //    }
}

pub fn single_output_change_strategy<DbT: InputSource>(
    fee_rule: StandardFeeRule,
    change_memo: Option<&str>,
    fallback_change_pool: ShieldedPool,
) -> standard::SingleOutputChangeStrategy<DbT> {
    let change_memo = change_memo.map(|m| MemoBytes::from(m.parse::<Memo>().unwrap()));
    standard::SingleOutputChangeStrategy::new(
        fee_rule,
        change_memo,
        fallback_change_pool,
        DustOutputPolicy::default(),
    )
}

// Checks that a protobuf proposal serialized from the provided proposal value correctly parses to
// the same proposal value.
fn check_proposal_serialization_roundtrip<ParamsT: consensus::Parameters, DbT: InputSource>(
    params: &ParamsT,
    wallet_data: &DbT,
    proposal: &Proposal<StandardFeeRule, DbT::NoteRef>,
) {
    let proposal_proto = crate::proto::proposal::Proposal::from_standard_proposal(proposal);
    let deserialized_proposal = proposal_proto.try_into_standard_proposal(params, wallet_data);
    assert_matches!(deserialized_proposal, Ok(r) if &r == proposal);
}

/// The initial chain state for a test.
///
/// This is returned from the closure passed to [`TestBuilder::with_initial_chain_state`]
/// to configure the test state with a starting chain position, to which subsequent test
/// activity is applied.
pub struct InitialChainState {
    /// Information about the chain's state as of the chain tip.
    pub chain_state: ChainState,
    /// Roots of the completed Sapling subtrees as of this chain state.
    pub prior_sapling_roots: Vec<CommitmentTreeRoot<::sapling::Node>>,
    /// Roots of the completed Orchard subtrees as of this chain state.
    #[cfg(feature = "orchard")]
    pub prior_orchard_roots: Vec<CommitmentTreeRoot<MerkleHashOrchard>>,
}

/// Trait representing the ability to construct a new data store for use in a test.
pub trait DataStoreFactory {
    type Error: core::fmt::Debug;
    type AccountId: std::fmt::Debug
        + ConditionallySelectable
        + Default
        + Hash
        + Eq
        + Send
        + Sync
        + 'static;
    type Account: Account<AccountId = Self::AccountId> + Clone;
    type DsError: core::fmt::Debug;
    type DataStore: InputSource<AccountId = Self::AccountId, Error = Self::DsError>
        + WalletRead<AccountId = Self::AccountId, Account = Self::Account, Error = Self::DsError>
        + WalletTest
        + WalletWrite
        + WalletCommitmentTrees;

    /// Constructs a new data store.
    fn new_data_store(
        &self,
        network: LocalNetwork,
        anchor_retention_interval: Option<AnchorRetentionInterval>,
        #[cfg(feature = "transparent-inputs")] gap_limits: Option<GapLimits>,
    ) -> Result<Self::DataStore, Self::Error>;
}

/// A [`TestState`] builder, that configures the environment for a test.
pub struct TestBuilder<Cache, DataStoreFactory> {
    rng: TestRng,
    network: LocalNetwork,
    cache: Cache,
    ds_factory: DataStoreFactory,
    initial_chain_state: Option<InitialChainState>,
    account_birthday: Option<AccountBirthday>,
    account_index: Option<zip32::AccountId>,
    anchor_retention_interval: Option<AnchorRetentionInterval>,
    #[cfg(feature = "transparent-inputs")]
    gap_limits: Option<GapLimits>,
}

impl TestBuilder<(), ()> {
    /// The default network used by [`TestBuilder::new`].
    ///
    /// This is a fake network where Sapling through NU5 activate at the same height. We
    /// pick height 100,000 to be large enough to handle any hard-coded test offsets.
    pub const DEFAULT_NETWORK: LocalNetwork = LocalNetwork {
        overwinter: Some(BlockHeight::from_u32(1)),
        sapling: Some(BlockHeight::from_u32(100_000)),
        blossom: Some(BlockHeight::from_u32(100_000)),
        heartwood: Some(BlockHeight::from_u32(100_000)),
        canopy: Some(BlockHeight::from_u32(100_000)),
        nu5: Some(BlockHeight::from_u32(100_000)),
        nu6: None,
        nu6_1: None,
        nu6_2: None,
        nu6_3: None,
        #[cfg(zcash_unstable = "nu7")]
        nu7: None,
    };

    /// Constructs a new test environment builder.
    pub fn new() -> Self {
        TestBuilder {
            rng: TestRng::seed_from_u64(0),
            network: Self::DEFAULT_NETWORK,
            cache: (),
            ds_factory: (),
            initial_chain_state: None,
            account_birthday: None,
            account_index: None,
            anchor_retention_interval: None,
            #[cfg(feature = "transparent-inputs")]
            gap_limits: None,
        }
    }
}

impl Default for TestBuilder<(), ()> {
    fn default() -> Self {
        Self::new()
    }
}

impl<A> TestBuilder<(), A> {
    /// Adds a block cache to the test environment.
    pub fn with_block_cache<C>(self, cache: C) -> TestBuilder<C, A> {
        TestBuilder {
            rng: self.rng,
            network: self.network,
            cache,
            ds_factory: self.ds_factory,
            initial_chain_state: self.initial_chain_state,
            account_birthday: self.account_birthday,
            account_index: self.account_index,
            anchor_retention_interval: self.anchor_retention_interval,
            #[cfg(feature = "transparent-inputs")]
            gap_limits: self.gap_limits,
        }
    }
}

impl<A> TestBuilder<A, ()> {
    /// Adds a wallet data store to the test environment.
    pub fn with_data_store_factory<DsFactory>(
        self,
        ds_factory: DsFactory,
    ) -> TestBuilder<A, DsFactory> {
        TestBuilder {
            rng: self.rng,
            network: self.network,
            cache: self.cache,
            ds_factory,
            initial_chain_state: self.initial_chain_state,
            account_birthday: self.account_birthday,
            account_index: self.account_index,
            anchor_retention_interval: self.anchor_retention_interval,
            #[cfg(feature = "transparent-inputs")]
            gap_limits: self.gap_limits,
        }
    }
}

impl<A, B> TestBuilder<A, B> {
    /// Overrides the network parameters used by the test (the default is
    /// [`TestBuilder::DEFAULT_NETWORK`]). This must be called before the account birthday is
    /// established (i.e. before `with_account_from_sapling_activation` /
    /// `with_account_having_current_birthday`), because the birthday is derived from the network's
    /// activation heights.
    pub fn with_network(mut self, network: LocalNetwork) -> Self {
        self.network = network;
        self
    }

    /// Overrides the interval on which the wallet retains durable anchor checkpoints (the default
    /// is [`AnchorRetentionInterval::ZIP_318`]).
    ///
    /// A test that must scan past a retained anchor otherwise has to generate 144 blocks per
    /// boundary; a short interval makes the same coverage cheap.
    pub fn with_anchor_retention_interval(mut self, interval: AnchorRetentionInterval) -> Self {
        self.anchor_retention_interval = Some(interval);
        self
    }

    #[cfg(feature = "transparent-inputs")]
    pub fn with_gap_limits(self, gap_limits: GapLimits) -> TestBuilder<A, B> {
        TestBuilder {
            rng: self.rng,
            network: self.network,
            cache: self.cache,
            ds_factory: self.ds_factory,
            initial_chain_state: self.initial_chain_state,
            account_birthday: self.account_birthday,
            account_index: self.account_index,
            anchor_retention_interval: self.anchor_retention_interval,
            gap_limits: Some(gap_limits),
        }
    }
}

impl<Cache, DsFactory> TestBuilder<Cache, DsFactory> {
    /// Configures the test to start with the given initial chain state.
    ///
    /// # Panics
    ///
    /// - Must not be called twice.
    /// - Must be called before [`Self::with_account_from_sapling_activation`] or
    ///   [`Self::with_account_having_current_birthday`].
    ///
    /// # Examples
    ///
    /// ```
    /// use std::num::NonZeroU8;
    ///
    /// use incrementalmerkletree::frontier::Frontier;
    /// use zcash_primitives::block::BlockHash;
    /// use zcash_protocol::consensus::{NetworkUpgrade, Parameters};
    /// use zcash_client_backend::data_api::{
    ///     chain::{ChainState, CommitmentTreeRoot},
    ///     testing::{
    ///         InitialChainState, TestBuilder, random_frontier_with_prior_subtree_roots,
    ///     },
    /// };
    ///
    /// // For this test, we'll start inserting leaf notes 5 notes after the end of the
    /// // third subtree, with a gap of 10 blocks. After `scan_cached_blocks`, the scan
    /// // queue should have a requested scan range of 300..310 with `FoundNote` priority,
    /// // 310..320 with `Scanned` priority. We set both Sapling and Orchard to the same
    /// // initial tree size for simplicity.
    /// let prior_block_hash = BlockHash([0; 32]);
    /// let initial_sapling_tree_size: u32 = (0x1 << 16) * 3 + 5;
    /// let initial_orchard_tree_size: u32 = (0x1 << 16) * 3 + 5;
    /// let initial_height_offset = 310;
    ///
    /// let mut st = TestBuilder::new()
    ///     .with_initial_chain_state(|rng, network| {
    ///         // For simplicity, assume Sapling and NU5 activated at the same height.
    ///         let sapling_activation_height =
    ///             network.activation_height(NetworkUpgrade::Sapling).unwrap();
    ///
    ///         // Construct a fake chain state for the end of block 300
    ///         let (prior_sapling_roots, sapling_initial_tree) =
    ///             random_frontier_with_prior_subtree_roots(
    ///                 rng,
    ///                 initial_sapling_tree_size.into(),
    ///                 NonZeroU8::new(16).unwrap(),
    ///                 |rng| sapling::Node::random(rng),
    ///             );
    ///         let prior_sapling_roots = prior_sapling_roots
    ///             .into_iter()
    ///             .zip(1u32..)
    ///             .map(|(root, i)| {
    ///                 CommitmentTreeRoot::from_parts(sapling_activation_height + (100 * i), root)
    ///             })
    ///             .collect::<Vec<_>>();
    ///
    ///         #[cfg(feature = "orchard")]
    ///         let (prior_orchard_roots, orchard_initial_tree) =
    ///             random_frontier_with_prior_subtree_roots(
    ///                 rng,
    ///                 initial_orchard_tree_size.into(),
    ///                 NonZeroU8::new(16).unwrap(),
    ///                 |rng| orchard::tree::MerkleHashOrchard::random(rng),
    ///             );
    ///         #[cfg(feature = "orchard")]
    ///         let prior_orchard_roots = prior_orchard_roots
    ///             .into_iter()
    ///             .zip(1u32..)
    ///             .map(|(root, i)| {
    ///                 CommitmentTreeRoot::from_parts(sapling_activation_height + (100 * i), root)
    ///             })
    ///             .collect::<Vec<_>>();
    ///
    ///         InitialChainState {
    ///             chain_state: ChainState::new(
    ///                 sapling_activation_height + initial_height_offset - 1,
    ///                 prior_block_hash,
    ///                 sapling_initial_tree,
    ///                 #[cfg(feature = "orchard")]
    ///                 orchard_initial_tree,
    ///                 #[cfg(feature = "orchard")]
    ///                 Frontier::empty(),
    ///             ),
    ///             prior_sapling_roots,
    ///             #[cfg(feature = "orchard")]
    ///             prior_orchard_roots,
    ///         }
    ///     });
    /// ```
    pub fn with_initial_chain_state(
        mut self,
        chain_state: impl FnOnce(&mut TestRng, &LocalNetwork) -> InitialChainState,
    ) -> Self {
        assert!(self.initial_chain_state.is_none());
        assert!(self.account_birthday.is_none());
        self.initial_chain_state = Some(chain_state(&mut self.rng, &self.network));
        self
    }

    /// Configures the environment with a [`TestAccount`] that has a birthday at Sapling
    /// activation.
    ///
    /// # Panics
    ///
    /// - Must not be called twice.
    /// - Do not call both [`Self::with_account_having_current_birthday`] and this method.
    pub fn with_account_from_sapling_activation(mut self, prev_hash: BlockHash) -> Self {
        assert!(self.account_birthday.is_none());
        self.account_birthday = Some(AccountBirthday::from_parts(
            ChainState::empty(
                self.network
                    .activation_height(NetworkUpgrade::Sapling)
                    .unwrap()
                    - 1,
                prev_hash,
            ),
            None,
        ));
        self
    }

    /// Configures the environment with a [`TestAccount`] that has a birthday one block
    /// after the initial chain state.
    ///
    /// # Panics
    ///
    /// - Must not be called twice.
    /// - Must call [`Self::with_initial_chain_state`] before calling this method.
    /// - Do not call both [`Self::with_account_from_sapling_activation`] and this method.
    pub fn with_account_having_current_birthday(mut self) -> Self {
        assert!(self.account_birthday.is_none());
        assert!(self.initial_chain_state.is_some());
        self.account_birthday = Some(AccountBirthday::from_parts(
            self.initial_chain_state
                .as_ref()
                .unwrap()
                .chain_state
                .clone(),
            None,
        ));
        self
    }

    /// Sets the account index for the test account.
    ///
    /// Does nothing unless either [`Self::with_account_from_sapling_activation`] or
    /// [`Self::with_account_having_current_birthday`] is also called.
    ///
    /// # Panics
    ///
    /// - Must not be called twice.
    pub fn set_account_index(mut self, index: zip32::AccountId) -> Self {
        assert!(self.account_index.is_none());
        self.account_index = Some(index);
        self
    }
}

impl<Cache, DsFactory: DataStoreFactory> TestBuilder<Cache, DsFactory> {
    /// Builds the state for this test.
    pub fn build(self) -> TestState<Cache, DsFactory::DataStore, LocalNetwork> {
        let mut cached_blocks = BTreeMap::new();
        let mut wallet_data = self
            .ds_factory
            .new_data_store(
                self.network,
                self.anchor_retention_interval,
                #[cfg(feature = "transparent-inputs")]
                self.gap_limits,
            )
            .unwrap();

        if let Some(initial_state) = &self.initial_chain_state {
            wallet_data
                .put_sapling_subtree_roots(0, &initial_state.prior_sapling_roots)
                .unwrap();
            wallet_data
                .with_sapling_tree_mut(|t| {
                    t.insert_frontier(
                        initial_state.chain_state.final_sapling_tree().clone(),
                        Retention::Checkpoint {
                            id: initial_state.chain_state.block_height(),
                            marking: Marking::Reference,
                        },
                    )
                })
                .unwrap();

            #[cfg(feature = "orchard")]
            {
                wallet_data
                    .put_orchard_subtree_roots(0, &initial_state.prior_orchard_roots)
                    .unwrap();
                wallet_data
                    .with_orchard_tree_mut(|t| {
                        t.insert_frontier(
                            initial_state.chain_state.final_orchard_tree().clone(),
                            Retention::Checkpoint {
                                id: initial_state.chain_state.block_height(),
                                marking: Marking::Reference,
                            },
                        )
                    })
                    .unwrap();
            }

            let final_sapling_tree_size =
                initial_state.chain_state.final_sapling_tree().tree_size() as u32;
            let _final_orchard_tree_size = 0;
            #[cfg(feature = "orchard")]
            let _final_orchard_tree_size =
                initial_state.chain_state.final_orchard_tree().tree_size() as u32;
            let _final_ironwood_tree_size = 0;
            #[cfg(feature = "orchard")]
            let _final_ironwood_tree_size =
                initial_state.chain_state.final_ironwood_tree().tree_size() as u32;

            cached_blocks.insert(
                initial_state.chain_state.block_height(),
                CachedBlock {
                    chain_state: initial_state.chain_state.clone(),
                    sapling_end_size: final_sapling_tree_size,
                    orchard_end_size: _final_orchard_tree_size,
                    ironwood_end_size: _final_ironwood_tree_size,
                },
            );
        };

        let test_account = self.account_birthday.map(|birthday| {
            let seed = Secret::new(vec![0u8; 32]);
            let (account, usk) = match self.account_index {
                Some(index) => wallet_data
                    .import_account_hd("", &seed, index, &birthday, None)
                    .expect("test account import succeeds"),
                None => {
                    let result = wallet_data
                        .create_account("", &seed, &birthday, None)
                        .expect("test account creation succeeds");
                    (
                        wallet_data
                            .get_account(result.0)
                            .expect("retrieval of just-created account succeeds")
                            .expect("an account was created"),
                        result.1,
                    )
                }
            };
            (
                seed,
                TestAccount {
                    account,
                    usk,
                    birthday,
                },
            )
        });

        TestState {
            cache: self.cache,
            cached_blocks,
            latest_block_height: self
                .initial_chain_state
                .map(|s| s.chain_state.block_height()),
            wallet_data,
            network: self.network,
            test_account,
            rng: self.rng,
        }
    }
}

/// Trait used by tests that require a full viewing key.
pub trait TestFvk: Clone {
    /// The type of nullifier corresponding to the kind of note that this full viewing key
    /// can detect (and that its corresponding spending key can spend).
    type Nullifier: Copy;
    /// The type of outgoing viewing key corresponding to this full viewing key;
    type OutgoingViewingKey;

    /// Returns the [`Self::OutgoingViewingKey`] corresponding to this full viewing key, for the
    /// given scope.
    fn to_ovk(&self, scope: zip32::Scope) -> Self::OutgoingViewingKey;

    /// Returns the bytes of the [`Self::OutgoingViewingKey`] corresponding to this full viewing
    /// key, for the given scope.
    fn ovk_bytes(&self, scope: zip32::Scope) -> [u8; 32];

    /// Adds a single spend to the given [`CompactTx`] of a note previously received by
    /// this full viewing key.
    fn add_spend<R: TestRngCore>(&self, ctx: &mut CompactTx, nf: Self::Nullifier, rng: &mut R);

    /// Adds a single output to the given [`CompactTx`], where the output will be discovered when
    /// scanning with an incoming viewing key corresponding to this FVK. Its outputs will also be
    /// discoverable when scanning with the provided OVK, if any.
    ///
    /// `recipient_address_type` allows configuring what shielded address to produce from this FVK
    /// as the recipient of the newly created output.
    ///
    /// Returns the nullifier of the newly created note, so that tests can readily have it on hand
    /// for the purpose of spending that note.
    #[allow(clippy::too_many_arguments)]
    fn add_output<P: consensus::Parameters, R: TestRngCore>(
        &self,
        ctx: &mut CompactTx,
        params: &P,
        height: BlockHeight,
        sender_ovk: Option<&Self::OutgoingViewingKey>,
        recipient_address_type: AddressType,
        value: Zatoshis,
        initial_sapling_tree_size: u32,
        // we don't require an initial Orchard tree size because we don't need it to compute
        // the nullifier.
        rng: &mut R,
    ) -> Self::Nullifier;

    /// Adds both a spend and an output to the given [`CompactTx`], where the output will be
    /// discovered when scanning with the incoming viewing key corresponding to this FVK. Its
    /// outputs will also be discoverable when scanning with the provided OVK, if any.
    ///
    /// - If this is a Sapling full viewing key, the transaction will gain both a Spend
    ///   and an Output.
    /// - If this is an Orchard full viewing key, the transaction will gain an Action.
    ///
    /// `recipient_address_type` allows configuring what shielded address to produce from this FVK as the
    /// recipient of the newly created output.
    ///
    /// Returns the nullifier full the newly created note which will need to be revealed when that
    /// note is later spent.
    #[allow(clippy::too_many_arguments)]
    fn add_logical_action<P: consensus::Parameters, R: TestRngCore>(
        &self,
        ctx: &mut CompactTx,
        params: &P,
        height: BlockHeight,
        nf_to_reveal_in_spend: Self::Nullifier,
        sender_ovk: Option<&Self::OutgoingViewingKey>,
        recipient_address_type: AddressType,
        value: Zatoshis,
        initial_sapling_tree_size: u32,
        // we don't require an initial Orchard tree size because we don't need it to compute
        // the nullifier.
        rng: &mut R,
    ) -> Self::Nullifier;
}

impl<A: TestFvk> TestFvk for &A {
    type Nullifier = A::Nullifier;
    type OutgoingViewingKey = A::OutgoingViewingKey;

    fn to_ovk(&self, scope: zip32::Scope) -> Self::OutgoingViewingKey {
        (*self).to_ovk(scope)
    }

    fn ovk_bytes(&self, scope: zip32::Scope) -> [u8; 32] {
        (*self).ovk_bytes(scope)
    }

    fn add_spend<R: TestRngCore>(&self, ctx: &mut CompactTx, nf: Self::Nullifier, rng: &mut R) {
        (*self).add_spend(ctx, nf, rng)
    }

    fn add_output<P: consensus::Parameters, R: TestRngCore>(
        &self,
        ctx: &mut CompactTx,
        params: &P,
        height: BlockHeight,
        sender_ovk: Option<&Self::OutgoingViewingKey>,
        recipient_address_type: AddressType,
        value: Zatoshis,
        initial_sapling_tree_size: u32,
        // we don't require an initial Orchard tree size because we don't need it to compute
        // the nullifier.
        rng: &mut R,
    ) -> Self::Nullifier {
        (*self).add_output(
            ctx,
            params,
            height,
            sender_ovk,
            recipient_address_type,
            value,
            initial_sapling_tree_size,
            rng,
        )
    }

    fn add_logical_action<P: consensus::Parameters, R: TestRngCore>(
        &self,
        ctx: &mut CompactTx,
        params: &P,
        height: BlockHeight,
        nf_to_reveal_in_spend: Self::Nullifier,
        sender_ovk: Option<&Self::OutgoingViewingKey>,
        recipient_address_type: AddressType,
        value: Zatoshis,
        initial_sapling_tree_size: u32,
        // we don't require an initial Orchard tree size because we don't need it to compute
        // the nullifier.
        rng: &mut R,
    ) -> Self::Nullifier {
        (*self).add_logical_action(
            ctx,
            params,
            height,
            nf_to_reveal_in_spend,
            sender_ovk,
            recipient_address_type,
            value,
            initial_sapling_tree_size,
            rng,
        )
    }
}

impl TestFvk for DiversifiableFullViewingKey {
    type Nullifier = ::sapling::Nullifier;
    type OutgoingViewingKey = ::sapling::keys::OutgoingViewingKey;

    fn to_ovk(&self, scope: zip32::Scope) -> Self::OutgoingViewingKey {
        self.to_ovk(scope)
    }

    fn ovk_bytes(&self, scope: zip32::Scope) -> [u8; 32] {
        self.to_ovk(scope).0
    }

    fn add_spend<R: TestRngCore>(&self, ctx: &mut CompactTx, nf: Self::Nullifier, _: &mut R) {
        let cspend = CompactSaplingSpend { nf: nf.to_vec() };
        ctx.spends.push(cspend);
    }

    fn add_output<P: consensus::Parameters, R: TestRngCore>(
        &self,
        ctx: &mut CompactTx,
        params: &P,
        height: BlockHeight,
        sender_ovk: Option<&Self::OutgoingViewingKey>,
        recipient_address_type: AddressType,
        value: Zatoshis,
        initial_sapling_tree_size: u32,
        rng: &mut R,
    ) -> Self::Nullifier {
        let recipient = match recipient_address_type {
            AddressType::DefaultExternal => self.default_address().1,
            AddressType::DiversifiedExternal(idx) => self.find_address(idx).unwrap().1,
            AddressType::Internal => self.change_address().1,
        };

        let position = initial_sapling_tree_size + ctx.outputs.len() as u32;

        let (cout, note) =
            compact_sapling_output(params, height, recipient, value, sender_ovk.copied(), rng);
        ctx.outputs.push(cout);

        note.nf(&self.fvk().vk.nk, u64::from(position))
    }

    #[allow(clippy::too_many_arguments)]
    fn add_logical_action<P: consensus::Parameters, R: TestRngCore>(
        &self,
        ctx: &mut CompactTx,
        params: &P,
        height: BlockHeight,
        nf_to_reveal_in_spend: Self::Nullifier,
        sender_ovk: Option<&Self::OutgoingViewingKey>,
        recipient_address_type: AddressType,
        value: Zatoshis,
        initial_sapling_tree_size: u32,
        rng: &mut R,
    ) -> Self::Nullifier {
        self.add_spend(ctx, nf_to_reveal_in_spend, rng);
        self.add_output(
            ctx,
            params,
            height,
            sender_ovk,
            recipient_address_type,
            value,
            initial_sapling_tree_size,
            rng,
        )
    }
}

#[cfg(feature = "orchard")]
impl TestFvk for ::orchard::keys::FullViewingKey {
    type Nullifier = ::orchard::note::Nullifier;
    type OutgoingViewingKey = ::orchard::keys::OutgoingViewingKey;

    fn to_ovk(&self, scope: zip32::Scope) -> Self::OutgoingViewingKey {
        self.to_ovk(scope)
    }

    fn ovk_bytes(&self, scope: zip32::Scope) -> [u8; 32] {
        *self.to_ovk(scope).as_ref()
    }

    fn add_spend<R: TestRngCore>(
        &self,
        ctx: &mut CompactTx,
        nullifier_to_reveal: Self::Nullifier,
        rng: &mut R,
    ) {
        // Generate a dummy recipient; the output will be zero-valued and be encrypted with a
        // random OVK.
        let recipient = loop {
            let mut bytes = [0; 32];
            RngCore08::fill_bytes(rng, &mut bytes);
            let sk = ::orchard::keys::SpendingKey::from_bytes(bytes);
            if sk.is_some().into() {
                break ::orchard::keys::FullViewingKey::from(&sk.unwrap())
                    .address_at(0u32, zip32::Scope::External);
            }
        };

        let (cact, _) =
            compact_orchard_action(nullifier_to_reveal, recipient, Zatoshis::ZERO, None, rng);
        ctx.actions.push(cact);
    }

    fn add_output<P: consensus::Parameters, R: TestRngCore>(
        &self,
        ctx: &mut CompactTx,
        _: &P,
        _: BlockHeight,
        sender_ovk: Option<&Self::OutgoingViewingKey>,
        recipient_address_type: AddressType,
        value: Zatoshis,
        _: u32, // the position is not required for computing the Orchard nullifier
        mut rng: &mut R,
    ) -> Self::Nullifier {
        // Generate a dummy nullifier for the spend
        let nullifier_to_reveal =
            ::orchard::note::Nullifier::from_bytes(&pallas::Base::random(&mut rng).to_repr())
                .unwrap();

        let (j, scope) = match recipient_address_type {
            AddressType::DefaultExternal => (0u32.into(), zip32::Scope::External),
            AddressType::DiversifiedExternal(idx) => (idx, zip32::Scope::External),
            AddressType::Internal => (0u32.into(), zip32::Scope::Internal),
        };

        let (cact, note) = compact_orchard_action(
            nullifier_to_reveal,
            self.address_at(j, scope),
            value,
            sender_ovk,
            rng,
        );
        ctx.actions.push(cact);

        note.nullifier(self)
    }

    fn add_logical_action<P: consensus::Parameters, R: TestRngCore>(
        &self,
        ctx: &mut CompactTx,
        _: &P,
        _: BlockHeight,
        nf_to_reveal_in_spend: Self::Nullifier,
        sender_ovk: Option<&Self::OutgoingViewingKey>,
        recipient_address_type: AddressType,
        value: Zatoshis,
        _: u32, // the position is not required for computing the Orchard nullifier
        rng: &mut R,
    ) -> Self::Nullifier {
        let (j, scope) = match recipient_address_type {
            AddressType::DefaultExternal => (0u32.into(), zip32::Scope::External),
            AddressType::DiversifiedExternal(idx) => (idx, zip32::Scope::External),
            AddressType::Internal => (0u32.into(), zip32::Scope::Internal),
        };

        let (cact, note) = compact_orchard_action(
            nf_to_reveal_in_spend,
            self.address_at(j, scope),
            value,
            sender_ovk,
            rng,
        );
        ctx.actions.push(cact);

        // Return the nullifier of the newly created output note
        note.nullifier(self)
    }
}

/// A test-only viewing key that receives Ironwood (version 3) notes. It wraps the account's Orchard
/// full viewing key, but its outputs are version 3 notes placed in `tx.ironwood_actions` and
/// encrypted under the Ironwood note-encryption domain, so a wallet scanning them exercises the
/// Ironwood receive path.
#[cfg(feature = "orchard")]
#[derive(Clone)]
pub struct IronwoodFvk(pub ::orchard::keys::FullViewingKey);

#[cfg(feature = "orchard")]
impl TestFvk for IronwoodFvk {
    type Nullifier = ::orchard::note::Nullifier;
    type OutgoingViewingKey = ::orchard::keys::OutgoingViewingKey;

    fn to_ovk(&self, scope: zip32::Scope) -> Self::OutgoingViewingKey {
        self.0.to_ovk(scope)
    }

    fn ovk_bytes(&self, scope: zip32::Scope) -> [u8; 32] {
        *self.0.to_ovk(scope).as_ref()
    }

    fn add_spend<R: TestRngCore>(
        &self,
        ctx: &mut CompactTx,
        nullifier_to_reveal: Self::Nullifier,
        rng: &mut R,
    ) {
        // Generate a dummy recipient; the output will be zero-valued and be encrypted with a
        // random OVK.
        let recipient = loop {
            let mut bytes = [0; 32];
            RngCore08::fill_bytes(rng, &mut bytes);
            let sk = ::orchard::keys::SpendingKey::from_bytes(bytes);
            if sk.is_some().into() {
                break ::orchard::keys::FullViewingKey::from(&sk.unwrap())
                    .address_at(0u32, zip32::Scope::External);
            }
        };

        let (cact, _) =
            compact_ironwood_action(nullifier_to_reveal, recipient, Zatoshis::ZERO, None, rng);
        ctx.ironwood_actions.push(cact);
    }

    fn add_output<P: consensus::Parameters, R: TestRngCore>(
        &self,
        ctx: &mut CompactTx,
        _: &P,
        _: BlockHeight,
        sender_ovk: Option<&Self::OutgoingViewingKey>,
        recipient_address_type: AddressType,
        value: Zatoshis,
        _: u32, // the position is not required for computing the Orchard nullifier
        mut rng: &mut R,
    ) -> Self::Nullifier {
        // Generate a dummy nullifier for the spend
        let nullifier_to_reveal =
            ::orchard::note::Nullifier::from_bytes(&pallas::Base::random(&mut rng).to_repr())
                .unwrap();

        let (j, scope) = match recipient_address_type {
            AddressType::DefaultExternal => (0u32.into(), zip32::Scope::External),
            AddressType::DiversifiedExternal(idx) => (idx, zip32::Scope::External),
            AddressType::Internal => (0u32.into(), zip32::Scope::Internal),
        };

        let (cact, note) = compact_ironwood_action(
            nullifier_to_reveal,
            self.0.address_at(j, scope),
            value,
            sender_ovk,
            rng,
        );
        ctx.ironwood_actions.push(cact);

        note.nullifier(&self.0)
    }

    fn add_logical_action<P: consensus::Parameters, R: TestRngCore>(
        &self,
        ctx: &mut CompactTx,
        _: &P,
        _: BlockHeight,
        nf_to_reveal_in_spend: Self::Nullifier,
        sender_ovk: Option<&Self::OutgoingViewingKey>,
        recipient_address_type: AddressType,
        value: Zatoshis,
        _: u32, // the position is not required for computing the Orchard nullifier
        rng: &mut R,
    ) -> Self::Nullifier {
        let (j, scope) = match recipient_address_type {
            AddressType::DefaultExternal => (0u32.into(), zip32::Scope::External),
            AddressType::DiversifiedExternal(idx) => (idx, zip32::Scope::External),
            AddressType::Internal => (0u32.into(), zip32::Scope::Internal),
        };

        let (cact, note) = compact_ironwood_action(
            nf_to_reveal_in_spend,
            self.0.address_at(j, scope),
            value,
            sender_ovk,
            rng,
        );
        ctx.ironwood_actions.push(cact);

        // Return the nullifier of the newly created output note
        note.nullifier(&self.0)
    }
}

/// Configures how a [`TestFvk`] receives a particular output.
///
/// Used with [`TestFvk::add_output`] and [`TestFvk::add_logical_action`].
#[derive(Clone, Copy, Debug)]
pub enum AddressType {
    /// The output will be sent to the default address of the full viewing key.
    DefaultExternal,
    /// The output will be sent to the specified diversified address of the full viewing
    /// key.
    #[allow(dead_code)]
    DiversifiedExternal(DiversifierIndex),
    /// The output will be sent to the internal receiver of the full viewing key.
    ///
    /// Such outputs are treated as "wallet-internal". A "recipient address" is **NEVER**
    /// exposed to users.
    Internal,
}

/// Creates a `CompactSaplingOutput` at the given height paying the given recipient.
///
/// Returns the `CompactSaplingOutput` and the new note.
fn compact_sapling_output<P: consensus::Parameters, R: TestRngCore>(
    params: &P,
    height: BlockHeight,
    recipient: ::sapling::PaymentAddress,
    value: Zatoshis,
    sender_ovk: Option<::sapling::keys::OutgoingViewingKey>,
    rng: &mut R,
) -> (CompactSaplingOutput, ::sapling::Note) {
    let rseed = generate_random_rseed(zip212_enforcement(params, height), rng);
    let note = ::sapling::Note::from_parts(
        recipient,
        ::sapling::value::NoteValue::from_raw(value.into_u64()),
        rseed,
    );
    let encryptor = sapling_note_encryption(
        sender_ovk,
        note.clone(),
        MemoBytes::empty().into_bytes(),
        rng,
    );
    let cmu = note.cmu().to_bytes().to_vec();
    let ephemeral_key = SaplingDomain::epk_bytes(encryptor.epk()).0.to_vec();
    let enc_ciphertext = encryptor.encrypt_note_plaintext();

    (
        CompactSaplingOutput {
            cmu,
            ephemeral_key,
            ciphertext: enc_ciphertext[..52].to_vec(),
        },
        note,
    )
}

/// Creates a `CompactOrchardAction` at the given height paying the given recipient.
///
/// Returns the `CompactOrchardAction` and the new note.
#[cfg(feature = "orchard")]
fn compact_orchard_action<R: TestRngCore>(
    nf_old: ::orchard::note::Nullifier,
    recipient: ::orchard::Address,
    value: Zatoshis,
    sender_ovk: Option<&::orchard::keys::OutgoingViewingKey>,
    rng: &mut R,
) -> (CompactOrchardAction, ::orchard::Note) {
    let (compact_action, note) = ::orchard::note_encryption::testing::fake_compact_action(
        rng,
        nf_old,
        recipient,
        ::orchard::value::NoteValue::from_raw(value.into_u64()),
        sender_ovk.cloned(),
    );

    (
        CompactOrchardAction {
            nullifier: compact_action.nullifier().to_bytes().to_vec(),
            cmx: compact_action.cmx().to_bytes().to_vec(),
            ephemeral_key:
                ShieldedOutput::<::orchard::note_encryption::OrchardDomain, 52>::ephemeral_key(
                    &compact_action,
                )
                .0
                .to_vec(),
            ciphertext:
                ShieldedOutput::<::orchard::note_encryption::OrchardDomain, 52>::enc_ciphertext(
                    &compact_action,
                )[..52]
                    .to_vec(),
        },
        note,
    )
}

/// Builds a version 3 (Ironwood) compact action paying `recipient` the given value, encrypted
/// under the Ironwood note-encryption domain, for placement in `tx.ironwood_actions`. Returns the
/// `CompactOrchardAction` and the note. This mirrors [`compact_orchard_action`], but constructs the
/// action directly because the orchard crate's `fake_compact_action` only produces version 2 notes.
#[cfg(feature = "orchard")]
fn compact_ironwood_action<R: TestRngCore>(
    nf_old: ::orchard::note::Nullifier,
    recipient: ::orchard::Address,
    value: Zatoshis,
    sender_ovk: Option<&::orchard::keys::OutgoingViewingKey>,
    rng: &mut R,
) -> (CompactOrchardAction, ::orchard::Note) {
    // Derive `rho` from the revealed nullifier exactly as the crate does internally
    // (`Rho::from_nf_old(nf) == Rho(nf.inner())`), so that the domain the scanner reconstructs via
    // `IronwoodDomain::for_compact_action(nf_old)` matches and decryption succeeds.
    let rho = Rho::from_bytes(&nf_old.to_bytes()).unwrap();
    let rseed = loop {
        let mut bytes = [0u8; 32];
        RngCore08::fill_bytes(rng, &mut bytes);
        if let Some(rseed) = Option::from(RandomSeed::from_bytes(bytes, &rho)) {
            break rseed;
        }
    };
    let note = OrchardNote::from_parts(
        recipient,
        ::orchard::value::NoteValue::from_raw(value.into_u64()),
        rho,
        rseed,
        NoteVersion::V3,
    )
    .unwrap();
    let encryptor = IronwoodNoteEncryption::new(sender_ovk.cloned(), note, [0u8; 512]);
    let cmx = ExtractedNoteCommitment::from(note.commitment());
    let ephemeral_key = IronwoodDomain::epk_bytes(encryptor.epk());
    let enc_ciphertext = encryptor.encrypt_note_plaintext();

    (
        CompactOrchardAction {
            nullifier: nf_old.to_bytes().to_vec(),
            cmx: cmx.to_bytes().to_vec(),
            ephemeral_key: ephemeral_key.0.to_vec(),
            ciphertext: enc_ciphertext[..52].to_vec(),
        },
        note,
    )
}

/// Creates a fake `CompactTx` with a random transaction ID and no spends or outputs.
fn fake_compact_tx<R: TestRngCore>(rng: &mut R) -> CompactTx {
    let mut ctx = CompactTx::default();
    let mut txid = vec![0; 32];
    RngCore08::fill_bytes(rng, &mut txid);
    ctx.txid = txid;

    ctx
}

/// A fake output of a [`CompactTx`].
///
/// Used with the following block generators:
/// - [`TestState::generate_next_block_multi`]
/// - [`TestState::generate_block_at`]
#[derive(Clone)]
pub struct FakeCompactOutput<Fvk> {
    recipient_fvk: Fvk,
    recipient_address_type: AddressType,
    value: Zatoshis,
}

impl<Fvk> FakeCompactOutput<Fvk> {
    /// Constructs a new fake output with the given properties.
    pub fn new(recipient_fvk: Fvk, recipient_address_type: AddressType, value: Zatoshis) -> Self {
        Self {
            recipient_fvk,
            recipient_address_type,
            value,
        }
    }

    /// Constructs a new random fake external output to the given FVK with a value in the range
    /// 10000..1000000 ZAT.
    pub fn random<R: RngCore08>(rng: &mut R, recipient_fvk: Fvk) -> Self {
        Self {
            recipient_fvk,
            recipient_address_type: AddressType::DefaultExternal,
            value: Zatoshis::const_from_u64(rng.gen_range(10000..1000000)),
        }
    }
}

/// Create a fake CompactBlock at the given height, containing the specified fake compact outputs.
///
/// Returns the newly created compact block, along with the nullifier for each note created in that
/// block.
#[allow(clippy::too_many_arguments)]
fn fake_compact_block<P: consensus::Parameters, Fvk: TestFvk>(
    params: &P,
    height: BlockHeight,
    prev_hash: BlockHash,
    sender_ovk: Option<&Fvk::OutgoingViewingKey>,
    outputs: &[FakeCompactOutput<Fvk>],
    initial_sapling_tree_size: u32,
    initial_orchard_tree_size: u32,
    initial_ironwood_tree_size: u32,
    mut rng: impl TestRngCore,
) -> (CompactBlock, Vec<Fvk::Nullifier>) {
    // Create a fake CompactBlock containing the note
    let mut ctx = fake_compact_tx(&mut rng);
    let mut nfs = vec![];
    for output in outputs {
        let nf = output.recipient_fvk.add_output(
            &mut ctx,
            params,
            height,
            sender_ovk,
            output.recipient_address_type,
            output.value,
            initial_sapling_tree_size,
            &mut rng,
        );
        nfs.push(nf);
    }

    let cb = fake_compact_block_from_compact_tx(
        ctx,
        height,
        prev_hash,
        initial_sapling_tree_size,
        initial_orchard_tree_size,
        initial_ironwood_tree_size,
        rng,
    );
    (cb, nfs)
}

/// Create a fake CompactBlock at the given height containing only the given transaction.
// TODO: `tx` could be a slice and we could add multiple transactions here
#[allow(clippy::too_many_arguments)]
fn fake_compact_block_from_tx(
    height: BlockHeight,
    prev_hash: BlockHash,
    tx_index: usize,
    tx: &Transaction,
    initial_sapling_tree_size: u32,
    initial_orchard_tree_size: u32,
    initial_ironwood_tree_size: u32,
    rng: impl RngCore08,
) -> CompactBlock {
    // Create a fake CompactTx containing the transaction.
    let mut ctx = CompactTx {
        index: tx_index as u64,
        txid: tx.txid().as_ref().to_vec(),
        ..Default::default()
    };

    if let Some(bundle) = tx.sapling_bundle() {
        for spend in bundle.shielded_spends() {
            ctx.spends.push(spend.into());
        }
        for output in bundle.shielded_outputs() {
            ctx.outputs.push(output.into());
        }
    }

    #[cfg(feature = "orchard")]
    if let Some(bundle) = tx.orchard_bundle() {
        for action in bundle.actions() {
            ctx.actions.push(action.into());
        }
    }

    #[cfg(feature = "orchard")]
    if let Some(bundle) = tx.ironwood_bundle() {
        for action in bundle.actions() {
            ctx.ironwood_actions.push(action.into());
        }
    }

    fake_compact_block_from_compact_tx(
        ctx,
        height,
        prev_hash,
        initial_sapling_tree_size,
        initial_orchard_tree_size,
        initial_ironwood_tree_size,
        rng,
    )
}

/// Create a fake CompactBlock at the given height, spending a single note from the
/// given address.
#[allow(clippy::too_many_arguments)]
fn fake_compact_block_spending<P: consensus::Parameters, Fvk: TestFvk>(
    params: &P,
    height: BlockHeight,
    prev_hash: BlockHash,
    (nf, in_value): (Fvk::Nullifier, Zatoshis),
    sender_fvk: &Fvk,
    to: Address,
    value: Zatoshis,
    initial_sapling_tree_size: u32,
    initial_orchard_tree_size: u32,
    initial_ironwood_tree_size: u32,
    mut rng: impl TestRngCore,
) -> CompactBlock {
    let mut ctx = fake_compact_tx(&mut rng);

    // Create a fake spend and a fake Note for the change
    sender_fvk.add_logical_action(
        &mut ctx,
        params,
        height,
        nf,
        Some(&sender_fvk.to_ovk(zip32::Scope::Internal)),
        AddressType::Internal,
        (in_value - value).unwrap(),
        initial_sapling_tree_size,
        &mut rng,
    );

    // Create a fake Note for the payment
    let ovk_bytes = sender_fvk.ovk_bytes(zip32::Scope::External);
    match to {
        Address::Sapling(recipient) => ctx.outputs.push(
            compact_sapling_output(
                params,
                height,
                recipient,
                value,
                Some(::sapling::keys::OutgoingViewingKey(ovk_bytes)),
                &mut rng,
            )
            .0,
        ),
        Address::Transparent(_) | Address::Tex(_) => {
            panic!("transparent addresses not supported in compact blocks")
        }
        Address::Unified(ua) => {
            // This is annoying to implement, because the protocol-aware UA type has no
            // concept of ZIP 316 preference order.
            let mut done = false;

            #[cfg(feature = "orchard")]
            if let Some(recipient) = ua.orchard() {
                // Generate a dummy nullifier
                let nullifier = ::orchard::note::Nullifier::from_bytes(
                    &pallas::Base::random(&mut rng).to_repr(),
                )
                .unwrap();

                ctx.actions.push(
                    compact_orchard_action(
                        nullifier,
                        *recipient,
                        value,
                        Some(&::orchard::keys::OutgoingViewingKey::from(ovk_bytes)),
                        &mut rng,
                    )
                    .0,
                );
                done = true;
            }

            if !done && let Some(recipient) = ua.sapling() {
                ctx.outputs.push(
                    compact_sapling_output(
                        params,
                        height,
                        *recipient,
                        value,
                        Some(::sapling::keys::OutgoingViewingKey(ovk_bytes)),
                        &mut rng,
                    )
                    .0,
                );
                done = true;
            }
            if !done {
                panic!("No supported shielded receiver to send funds to");
            }
        }
    }

    fake_compact_block_from_compact_tx(
        ctx,
        height,
        prev_hash,
        initial_sapling_tree_size,
        initial_orchard_tree_size,
        initial_ironwood_tree_size,
        rng,
    )
}

fn fake_compact_block_from_compact_tx(
    ctx: CompactTx,
    height: BlockHeight,
    prev_hash: BlockHash,
    initial_sapling_tree_size: u32,
    initial_orchard_tree_size: u32,
    initial_ironwood_tree_size: u32,
    mut rng: impl RngCore08,
) -> CompactBlock {
    let mut cb = CompactBlock {
        hash: {
            let mut hash = vec![0; 32];
            rng.fill_bytes(&mut hash);
            hash
        },
        height: height.into(),
        ..Default::default()
    };
    cb.prev_hash.extend_from_slice(&prev_hash.0);
    cb.vtx.push(ctx);
    cb.chain_metadata = Some(compact_formats::ChainMetadata {
        sapling_commitment_tree_size: initial_sapling_tree_size
            + cb.vtx.iter().map(|tx| tx.outputs.len() as u32).sum::<u32>(),
        orchard_commitment_tree_size: initial_orchard_tree_size
            + cb.vtx.iter().map(|tx| tx.actions.len() as u32).sum::<u32>(),
        ironwood_commitment_tree_size: initial_ironwood_tree_size
            + cb.vtx
                .iter()
                .map(|tx| tx.ironwood_actions.len() as u32)
                .sum::<u32>(),
    });
    cb
}

// A trait that must be implemented for all test caches, for returning metadata about inserted
// values.
pub trait CacheInsertionResult {
    fn txids(&self) -> &[TxId];
}

/// Trait used by tests that require a block cache.
pub trait TestCache {
    type BsError: core::fmt::Debug;
    type BlockSource: BlockSource<Error = Self::BsError>;
    type InsertResult: CacheInsertionResult;

    /// Exposes the block cache as a [`BlockSource`].
    fn block_source(&self) -> &Self::BlockSource;

    /// Inserts a CompactBlock into the cache DB.
    fn insert(&mut self, cb: &CompactBlock) -> Self::InsertResult;

    /// Deletes block data from the cache, retaining blocks at heights less than or equal to the
    /// specified height.
    fn truncate_to_height(&mut self, height: BlockHeight);
}

/// A convenience type for the note commitments contained within a [`CompactBlock`].
///
/// Indended for use as (part of) the [`TestCache::InsertResult`] associated type.
pub struct NoteCommitments {
    sapling: Vec<::sapling::Node>,
    #[cfg(feature = "orchard")]
    orchard: Vec<MerkleHashOrchard>,
}

impl NoteCommitments {
    /// Extracts the note commitments from the given compact block.
    pub fn from_compact_block(cb: &CompactBlock) -> Self {
        NoteCommitments {
            sapling: cb
                .vtx
                .iter()
                .flat_map(|tx| {
                    tx.outputs
                        .iter()
                        .map(|out| ::sapling::Node::from_cmu(&out.cmu().unwrap()))
                })
                .collect(),
            #[cfg(feature = "orchard")]
            orchard: cb
                .vtx
                .iter()
                .flat_map(|tx| {
                    tx.actions
                        .iter()
                        .map(|act| MerkleHashOrchard::from_cmx(&act.cmx().unwrap()))
                })
                .collect(),
        }
    }

    /// Returns the Sapling note commitments.
    #[allow(dead_code)]
    pub fn sapling(&self) -> &[::sapling::Node] {
        self.sapling.as_ref()
    }

    /// Returns the Orchard note commitments.
    #[cfg(feature = "orchard")]
    pub fn orchard(&self) -> &[MerkleHashOrchard] {
        self.orchard.as_ref()
    }
}

/// A mock wallet data source that implements the bare minimum necessary to function.
pub struct MockWalletDb {
    pub network: Network,
    pub sapling_tree: ShardTree<
        MemoryShardStore<::sapling::Node, BlockHeight>,
        { SAPLING_SHARD_HEIGHT * 2 },
        SAPLING_SHARD_HEIGHT,
    >,
    #[cfg(feature = "orchard")]
    pub orchard_tree: ShardTree<
        MemoryShardStore<::orchard::tree::MerkleHashOrchard, BlockHeight>,
        { ORCHARD_SHARD_HEIGHT * 2 },
        ORCHARD_SHARD_HEIGHT,
    >,
    account_ids: Vec<u32>,
    addresses_by_account: HashMap<u32, Vec<AddressInfo>>,
    ufvks_by_account: HashMap<u32, UnifiedFullViewingKey>,
}

impl MockWalletDb {
    /// Constructs a new mock wallet data source.
    pub fn new(network: Network) -> Self {
        Self {
            network,
            sapling_tree: ShardTree::new(MemoryShardStore::empty(), 100),
            #[cfg(feature = "orchard")]
            orchard_tree: ShardTree::new(MemoryShardStore::empty(), 100),
            account_ids: vec![],
            addresses_by_account: HashMap::new(),
            ufvks_by_account: HashMap::new(),
        }
    }

    #[cfg(test)]
    pub(crate) fn from_account_addresses(
        network: Network,
        entries: impl IntoIterator<Item = (u32, Vec<AddressInfo>)>,
    ) -> Self {
        let mut wallet = Self::new(network);
        for (account_id, addresses) in entries {
            wallet.account_ids.push(account_id);
            wallet.addresses_by_account.insert(account_id, addresses);
        }
        wallet.account_ids.sort_unstable();
        wallet
    }

    #[cfg(test)]
    pub(crate) fn from_account_ufvks(
        network: Network,
        entries: impl IntoIterator<Item = (u32, UnifiedFullViewingKey)>,
    ) -> Self {
        let mut wallet = Self::new(network);
        for (account_id, ufvk) in entries {
            wallet.account_ids.push(account_id);
            wallet.ufvks_by_account.insert(account_id, ufvk);
        }
        wallet.account_ids.sort_unstable();
        wallet
    }
}

impl InputSource for MockWalletDb {
    type Error = ();
    type NoteRef = u32;
    type AccountId = u32;

    fn anchor_computable(
        &self,
        protocol: ShieldedPool,
        height: BlockHeight,
    ) -> Result<bool, Self::Error> {
        match protocol {
            ShieldedPool::Sapling => Ok(self
                .sapling_tree
                .store()
                .get_checkpoint(&height)
                .map_err(|_| ())?
                .is_some()),
            #[cfg(feature = "orchard")]
            ShieldedPool::Orchard => Ok(self
                .orchard_tree
                .store()
                .get_checkpoint(&height)
                .map_err(|_| ())?
                .is_some()),
            // The mock maintains no Ironwood tree (and no Orchard tree without the `orchard`
            // feature), so no anchor is computable there.
            _ => Ok(false),
        }
    }

    fn get_spendable_note(
        &self,
        _txid: &TxId,
        _protocol: ShieldedPool,
        _index: u32,
        _target_height: TargetHeight,
        _lock_filter: LockFilter<'_>,
    ) -> Result<Option<ReceivedNote<Self::NoteRef, Note>>, Self::Error> {
        Ok(None)
    }

    fn select_spendable_notes(
        &self,
        _account: Self::AccountId,
        _target_value: TargetValue,
        _sources: &[ShieldedPool],
        _target_height: TargetHeight,
        _confirmations_policy: ConfirmationsPolicy,
        _exclude: &[Self::NoteRef],
        _lock_filter: LockFilter<'_>,
    ) -> Result<ReceivedNotes<Self::NoteRef>, Self::Error> {
        Ok(ReceivedNotes::empty())
    }

    fn select_unspent_notes(
        &self,
        _account: Self::AccountId,
        _sources: &[ShieldedPool],
        _target_height: TargetHeight,
        _exclude: &[Self::NoteRef],
        _lock_filter: LockFilter<'_>,
    ) -> Result<ReceivedNotes<Self::NoteRef>, Self::Error> {
        Err(())
    }

    fn get_account_metadata(
        &self,
        _account: Self::AccountId,
        _selector: &NoteFilter,
        _target_height: TargetHeight,
        _exclude: &[Self::NoteRef],
        _lock_filter: LockFilter<'_>,
    ) -> Result<AccountMeta, Self::Error> {
        Err(())
    }
}

impl WalletRead for MockWalletDb {
    type Error = ();
    type AccountId = u32;
    type Account = (Self::AccountId, UnifiedFullViewingKey, BlockHeight);

    fn get_account_ids(&self) -> Result<Vec<Self::AccountId>, Self::Error> {
        Ok(self.account_ids.clone())
    }

    fn get_account(
        &self,
        account_id: Self::AccountId,
    ) -> Result<Option<Self::Account>, Self::Error> {
        Ok(self
            .ufvks_by_account
            .get(&account_id)
            .cloned()
            .map(|ufvk| (account_id, ufvk, BlockHeight::from(1))))
    }

    fn get_derived_account(
        &self,
        _derivation: &Zip32Derivation,
    ) -> Result<Option<Self::Account>, Self::Error> {
        Ok(None)
    }

    fn validate_seed(
        &self,
        _account_id: Self::AccountId,
        _seed: &SecretVec<u8>,
    ) -> Result<bool, Self::Error> {
        Ok(false)
    }

    fn seed_relevance_to_derived_accounts(
        &self,
        _seed: &SecretVec<u8>,
    ) -> Result<SeedRelevance<Self::AccountId>, Self::Error> {
        Ok(SeedRelevance::NoAccounts)
    }

    fn get_account_for_ufvk(
        &self,
        _ufvk: &UnifiedFullViewingKey,
    ) -> Result<Option<Self::Account>, Self::Error> {
        Ok(None)
    }

    fn list_addresses(&self, account: Self::AccountId) -> Result<Vec<AddressInfo>, Self::Error> {
        Ok(self
            .addresses_by_account
            .get(&account)
            .cloned()
            .unwrap_or_default())
    }

    fn find_account_for_address<P: consensus::Parameters>(
        &self,
        params: &P,
        address: &zcash_keys::address::Address,
    ) -> Result<Option<Self::AccountId>, super::error::FindAccountForAddressError<Self::Error>>
    {
        super::defaults::find_account_for_address(self, params, address)
    }

    fn get_last_generated_address_matching(
        &self,
        _account: Self::AccountId,
        _request: UnifiedAddressRequest,
    ) -> Result<Option<UnifiedAddress>, Self::Error> {
        Ok(None)
    }

    fn get_account_birthday(&self, _account: Self::AccountId) -> Result<BlockHeight, Self::Error> {
        Err(())
    }

    fn get_wallet_birthday(&self) -> Result<Option<BlockHeight>, Self::Error> {
        Ok(None)
    }

    fn get_wallet_recover_until(&self) -> Result<Option<BlockHeight>, Self::Error> {
        Ok(None)
    }

    fn get_wallet_summary(
        &self,
        _confirmations_policy: ConfirmationsPolicy,
    ) -> Result<Option<WalletSummary<Self::AccountId>>, Self::Error> {
        Ok(None)
    }

    fn chain_height(&self) -> Result<Option<BlockHeight>, Self::Error> {
        Ok(None)
    }

    fn get_block_hash(&self, _block_height: BlockHeight) -> Result<Option<BlockHash>, Self::Error> {
        Ok(None)
    }

    fn block_metadata(&self, _height: BlockHeight) -> Result<Option<BlockMetadata>, Self::Error> {
        Ok(None)
    }

    fn block_fully_scanned(&self) -> Result<Option<BlockMetadata>, Self::Error> {
        Ok(None)
    }

    fn get_max_height_hash(&self) -> Result<Option<(BlockHeight, BlockHash)>, Self::Error> {
        Ok(None)
    }

    fn block_max_scanned(&self) -> Result<Option<BlockMetadata>, Self::Error> {
        Ok(None)
    }

    fn suggest_scan_ranges(&self) -> Result<Vec<ScanRange>, Self::Error> {
        Ok(vec![])
    }

    fn get_target_and_anchor_heights(
        &self,
        _min_confirmations: NonZeroU32,
    ) -> Result<Option<(TargetHeight, BlockHeight)>, Self::Error> {
        Ok(None)
    }

    fn get_tx_height(&self, _txid: TxId) -> Result<Option<BlockHeight>, Self::Error> {
        Ok(None)
    }

    fn get_unified_full_viewing_keys(
        &self,
    ) -> Result<HashMap<Self::AccountId, UnifiedFullViewingKey>, Self::Error> {
        Ok(HashMap::new())
    }

    fn get_memo(&self, _id_note: NoteId) -> Result<Option<Memo>, Self::Error> {
        Ok(None)
    }

    fn get_transaction(&self, _txid: TxId) -> Result<Option<Transaction>, Self::Error> {
        Ok(None)
    }

    fn get_sapling_nullifiers(
        &self,
        _query: NullifierQuery,
    ) -> Result<Vec<(Self::AccountId, ::sapling::Nullifier)>, Self::Error> {
        Ok(Vec::new())
    }

    #[cfg(feature = "orchard")]
    fn get_orchard_nullifiers(
        &self,
        _query: NullifierQuery,
    ) -> Result<Vec<(Self::AccountId, ::orchard::note::Nullifier)>, Self::Error> {
        Ok(Vec::new())
    }

    #[cfg(feature = "orchard")]
    fn get_ironwood_nullifiers(
        &self,
        _query: NullifierQuery,
    ) -> Result<Vec<(Self::AccountId, ::orchard::note::Nullifier)>, Self::Error> {
        Ok(Vec::new())
    }

    #[cfg(feature = "transparent-inputs")]
    fn get_transparent_receivers(
        &self,
        _account: Self::AccountId,
        _include_change: bool,
        _include_standalone: bool,
    ) -> Result<HashMap<TransparentAddress, TransparentAddressMetadata>, Self::Error> {
        Ok(HashMap::new())
    }

    #[cfg(feature = "transparent-inputs")]
    fn get_transparent_balances(
        &self,
        _account: Self::AccountId,
        _target_height: TargetHeight,
        _confirmations_policy: ConfirmationsPolicy,
    ) -> Result<TransparentBalances, Self::Error> {
        Ok(HashMap::new())
    }

    #[cfg(feature = "transparent-inputs")]
    fn get_transparent_address_metadata(
        &self,
        _account: Self::AccountId,
        _address: &TransparentAddress,
    ) -> Result<Option<TransparentAddressMetadata>, Self::Error> {
        Ok(None)
    }

    #[cfg(feature = "transparent-inputs")]
    fn utxo_query_height(&self, _account: Self::AccountId) -> Result<BlockHeight, Self::Error> {
        Ok(BlockHeight::from(0u32))
    }

    fn transaction_data_requests(&self) -> Result<Vec<TransactionDataRequest>, Self::Error> {
        Ok(vec![])
    }

    fn get_received_outputs(
        &self,
        _txid: TxId,
        _target_height: TargetHeight,
        _confirmations_policy: ConfirmationsPolicy,
    ) -> Result<Vec<ReceivedTransactionOutput>, Self::Error> {
        Ok(vec![])
    }
}

impl OutputLockStore for MockWalletDb {
    type Error = ();
    type AccountId = u32;

    fn lock_outputs(
        &mut self,
        _outputs: &[OutputRef],
        _owner: LockOwner,
        _lock_expiry_height: BlockHeight,
    ) -> Result<usize, LockError<Self::Error>> {
        Ok(0)
    }

    fn unlock_output(
        &mut self,
        _output: &OutputRef,
        _owner: LockOwner,
    ) -> Result<bool, Self::Error> {
        Ok(false)
    }

    fn clear_locked_outputs(&mut self, _account: Self::AccountId) -> Result<usize, Self::Error> {
        Ok(0)
    }

    fn get_locked_outputs(&self, _account: Self::AccountId) -> Result<Vec<OutputRef>, Self::Error> {
        Ok(Vec::new())
    }
}

impl WalletWrite for MockWalletDb {
    type UtxoRef = u32;

    fn create_account(
        &mut self,
        _account_name: &str,
        seed: &SecretVec<u8>,
        _birthday: &AccountBirthday,
        _key_source: Option<&str>,
    ) -> Result<(<Self as WalletRead>::AccountId, UnifiedSpendingKey), <Self as WalletRead>::Error>
    {
        let account = zip32::AccountId::ZERO;
        UnifiedSpendingKey::from_seed(&self.network, seed.expose_secret(), account)
            .map(|k| (u32::from(account), k))
            .map_err(|_| ())
    }

    fn import_account_hd(
        &mut self,
        _account_name: &str,
        _seed: &SecretVec<u8>,
        _account_index: zip32::AccountId,
        _birthday: &AccountBirthday,
        _key_source: Option<&str>,
    ) -> Result<(Self::Account, UnifiedSpendingKey), <Self as WalletRead>::Error> {
        todo!()
    }

    fn import_account_ufvk(
        &mut self,
        _account_name: &str,
        _unified_key: &UnifiedFullViewingKey,
        _birthday: &AccountBirthday,
        _purpose: AccountPurpose,
        _key_source: Option<&str>,
    ) -> Result<Self::Account, <Self as WalletRead>::Error> {
        todo!()
    }

    fn delete_account(
        &mut self,
        _account: <Self as WalletRead>::AccountId,
    ) -> Result<(), <Self as WalletRead>::Error> {
        todo!()
    }

    #[cfg(feature = "transparent-key-import")]
    fn import_standalone_transparent_pubkey(
        &mut self,
        _account: <Self as WalletRead>::AccountId,
        _address: secp256k1::PublicKey,
    ) -> Result<(), <Self as WalletRead>::Error> {
        todo!()
    }

    #[cfg(feature = "transparent-key-import")]
    fn import_standalone_transparent_script(
        &mut self,
        _account: <Self as WalletRead>::AccountId,
        _script: script::Redeem,
    ) -> Result<(), <Self as WalletRead>::Error> {
        todo!()
    }

    fn get_next_available_address(
        &mut self,
        _account: <Self as WalletRead>::AccountId,
        _request: UnifiedAddressRequest,
    ) -> Result<Option<(UnifiedAddress, DiversifierIndex)>, <Self as WalletRead>::Error> {
        Ok(None)
    }

    fn get_address_for_index(
        &mut self,
        _account: <Self as WalletRead>::AccountId,
        _diversifier_index: DiversifierIndex,
        _request: UnifiedAddressRequest,
    ) -> Result<Option<UnifiedAddress>, <Self as WalletRead>::Error> {
        Ok(None)
    }

    #[allow(clippy::type_complexity)]
    fn put_blocks(
        &mut self,
        _from_state: &ChainState,
        _blocks: Vec<ScannedBlock<<Self as WalletRead>::AccountId>>,
    ) -> Result<(), <Self as WalletRead>::Error> {
        Ok(())
    }

    fn update_chain_tip(
        &mut self,
        _tip_height: BlockHeight,
    ) -> Result<(), <Self as WalletRead>::Error> {
        Ok(())
    }

    fn prune_scan_queue_below(
        &mut self,
        _height: BlockHeight,
        _retain_with_priority: Option<ScanPriority>,
    ) -> Result<u64, <Self as WalletRead>::Error> {
        Ok(0)
    }

    fn store_decrypted_tx(
        &mut self,
        _received_tx: DecryptedTransaction<Transaction, <Self as WalletRead>::AccountId>,
    ) -> Result<(), <Self as WalletRead>::Error> {
        Ok(())
    }

    fn set_tx_trust(
        &mut self,
        _txid: TxId,
        _trusted: bool,
    ) -> Result<(), <Self as WalletRead>::Error> {
        Ok(())
    }

    fn store_transactions_to_be_sent(
        &mut self,
        _transactions: &[SentTransaction<<Self as WalletRead>::AccountId>],
    ) -> Result<(), <Self as WalletRead>::Error> {
        Ok(())
    }

    fn truncate_to_height(
        &mut self,
        _block_height: BlockHeight,
    ) -> Result<BlockHeight, <Self as WalletRead>::Error> {
        Err(())
    }

    fn truncate_to_chain_state(
        &mut self,
        _chain_state: ChainState,
    ) -> Result<(), <Self as WalletRead>::Error> {
        Err(())
    }

    fn rewind_to_chain_state(
        &mut self,
        _chain_state: ChainState,
        _reset_account_birthdays: HashSet<<Self as WalletRead>::AccountId>,
    ) -> Result<(), RewindError<<Self as WalletRead>::AccountId, <Self as WalletRead>::Error>> {
        Err(RewindError::DataSource(()))
    }

    /// Adds a transparent UTXO received by the wallet to the data store.
    fn put_received_transparent_utxo(
        &mut self,
        _output: &WalletTransparentOutput<<Self as WalletRead>::AccountId>,
    ) -> Result<Self::UtxoRef, <Self as WalletRead>::Error> {
        Ok(0)
    }

    #[cfg(feature = "transparent-inputs")]
    fn reserve_next_n_ephemeral_addresses(
        &mut self,
        _account_id: <Self as WalletRead>::AccountId,
        _n: usize,
    ) -> Result<Vec<(TransparentAddress, TransparentAddressMetadata)>, <Self as WalletRead>::Error>
    {
        Err(())
    }

    #[cfg(feature = "transparent-inputs")]
    fn reserve_next_n_internal_addresses(
        &mut self,
        _account_id: <Self as WalletRead>::AccountId,
        _n: usize,
    ) -> Result<Vec<(TransparentAddress, TransparentAddressMetadata)>, <Self as WalletRead>::Error>
    {
        Err(())
    }

    fn set_transaction_status(
        &mut self,
        _txid: TxId,
        _status: TransactionStatus,
    ) -> Result<(), <Self as WalletRead>::Error> {
        Ok(())
    }

    #[cfg(feature = "transparent-inputs")]
    fn notify_address_checked(
        &mut self,
        _request: TransactionsInvolvingAddress,
        _as_of_height: BlockHeight,
    ) -> Result<(), <Self as WalletRead>::Error> {
        Ok(())
    }
}

impl WalletCommitmentTrees for MockWalletDb {
    type Error = Infallible;
    type SaplingShardStore<'a> = MemoryShardStore<::sapling::Node, BlockHeight>;

    fn with_sapling_tree_mut<F, A, E>(&mut self, mut callback: F) -> Result<A, E>
    where
        for<'a> F: FnMut(
            &'a mut ShardTree<
                Self::SaplingShardStore<'a>,
                { ::sapling::NOTE_COMMITMENT_TREE_DEPTH },
                SAPLING_SHARD_HEIGHT,
            >,
        ) -> Result<A, E>,
        E: From<ShardTreeError<Infallible>>,
    {
        callback(&mut self.sapling_tree)
    }

    fn put_sapling_subtree_roots(
        &mut self,
        start_index: u64,
        roots: &[CommitmentTreeRoot<::sapling::Node>],
    ) -> Result<(), ShardTreeError<Self::Error>> {
        self.with_sapling_tree_mut(|t| {
            for (root, i) in roots.iter().zip(0u64..) {
                let root_addr = incrementalmerkletree::Address::from_parts(
                    SAPLING_SHARD_HEIGHT.into(),
                    start_index + i,
                );
                t.insert(root_addr, *root.root_hash())?;
            }
            Ok::<_, ShardTreeError<Self::Error>>(())
        })?;

        Ok(())
    }

    fn get_sapling_subtree_root(
        &mut self,
        index: u64,
    ) -> Result<Option<::sapling::Node>, ShardTreeError<Self::Error>> {
        self.with_sapling_tree_mut(|t| {
            let addr =
                incrementalmerkletree::Address::from_parts(SAPLING_SHARD_HEIGHT.into(), index);
            Ok::<_, ShardTreeError<Self::Error>>(
                t.store()
                    .get_shard(addr)
                    .map_err(ShardTreeError::Storage)?
                    .and_then(|shard| match shard.root() {
                        tree if tree.is_leaf() => tree.leaf_value().copied(),
                        tree => tree.annotation().and_then(|ann| ann.as_deref().copied()),
                    }),
            )
        })
    }

    #[cfg(feature = "orchard")]
    type OrchardShardStore<'a> = MemoryShardStore<::orchard::tree::MerkleHashOrchard, BlockHeight>;

    #[cfg(feature = "orchard")]
    fn with_orchard_tree_mut<F, A, E>(&mut self, mut callback: F) -> Result<A, E>
    where
        for<'a> F: FnMut(
            &'a mut ShardTree<
                Self::OrchardShardStore<'a>,
                { ORCHARD_SHARD_HEIGHT * 2 },
                ORCHARD_SHARD_HEIGHT,
            >,
        ) -> Result<A, E>,
        E: From<ShardTreeError<Self::Error>>,
    {
        callback(&mut self.orchard_tree)
    }

    /// Adds a sequence of note commitment tree subtree roots to the data store.
    #[cfg(feature = "orchard")]
    fn put_orchard_subtree_roots(
        &mut self,
        start_index: u64,
        roots: &[CommitmentTreeRoot<::orchard::tree::MerkleHashOrchard>],
    ) -> Result<(), ShardTreeError<Self::Error>> {
        self.with_orchard_tree_mut(|t| {
            for (root, i) in roots.iter().zip(0u64..) {
                let root_addr = incrementalmerkletree::Address::from_parts(
                    ORCHARD_SHARD_HEIGHT.into(),
                    start_index + i,
                );
                t.insert(root_addr, *root.root_hash())?;
            }
            Ok::<_, ShardTreeError<Self::Error>>(())
        })?;

        Ok(())
    }

    #[cfg(feature = "orchard")]
    fn get_orchard_subtree_root(
        &mut self,
        index: u64,
    ) -> Result<Option<::orchard::tree::MerkleHashOrchard>, ShardTreeError<Self::Error>> {
        self.with_orchard_tree_mut(|t| {
            let addr =
                incrementalmerkletree::Address::from_parts(ORCHARD_SHARD_HEIGHT.into(), index);
            Ok::<_, ShardTreeError<Self::Error>>(
                t.store()
                    .get_shard(addr)
                    .map_err(ShardTreeError::Storage)?
                    .and_then(|shard| match shard.root() {
                        tree if tree.is_leaf() => tree.leaf_value().copied(),
                        tree => tree.annotation().and_then(|ann| ann.as_deref().copied()),
                    }),
            )
        })
    }
}