tests: functional tests for Schnorr/Taproot/Tapscript

A large functional test is added that automatically generates random transactions which
exercise various aspects of the new rules, and verifies they are accepted into the mempool
(when appropriate), and correctly accepted/rejected in (Python-constructed) blocks.

Includes sighashing code and many tests by Johnson Lau.
Includes a test by Matthew Zipkin.
Includes several tests and improvements by Greg Sanders.

5 files changed, 1553 insertions, 17 deletions

diff --git a/test/functional/feature_taproot.py b/test/functional/feature_taproot.py
new file mode 100755
index 0000000000..146193d018
--- /dev/null
+++ b/test/functional/feature_taproot.py
@@ -0,0 +1,1411 @@
+#!/usr/bin/env python3
+# Copyright (c) 2019-2020 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+# Test Taproot softfork (BIPs 340-342)
+
+from test_framework.blocktools import (
+    create_coinbase,
+    create_block,
+    add_witness_commitment,
+    MAX_BLOCK_SIGOPS_WEIGHT,
+    WITNESS_SCALE_FACTOR,
+)
+from test_framework.messages import (
+    COutPoint,
+    CTransaction,
+    CTxIn,
+    CTxInWitness,
+    CTxOut,
+    ToHex,
+)
+from test_framework.script import (
+    ANNEX_TAG,
+    CScript,
+    CScriptNum,
+    CScriptOp,
+    LEAF_VERSION_TAPSCRIPT,
+    LegacySignatureHash,
+    LOCKTIME_THRESHOLD,
+    MAX_SCRIPT_ELEMENT_SIZE,
+    OP_0,
+    OP_1,
+    OP_2,
+    OP_3,
+    OP_4,
+    OP_5,
+    OP_6,
+    OP_7,
+    OP_8,
+    OP_9,
+    OP_10,
+    OP_11,
+    OP_12,
+    OP_16,
+    OP_2DROP,
+    OP_2DUP,
+    OP_CHECKMULTISIG,
+    OP_CHECKMULTISIGVERIFY,
+    OP_CHECKSIG,
+    OP_CHECKSIGADD,
+    OP_CHECKSIGVERIFY,
+    OP_CODESEPARATOR,
+    OP_DROP,
+    OP_DUP,
+    OP_ELSE,
+    OP_ENDIF,
+    OP_EQUAL,
+    OP_EQUALVERIFY,
+    OP_HASH160,
+    OP_IF,
+    OP_NOP,
+    OP_NOT,
+    OP_NOTIF,
+    OP_PUSHDATA1,
+    OP_RETURN,
+    OP_SWAP,
+    OP_VERIFY,
+    SIGHASH_DEFAULT,
+    SIGHASH_ALL,
+    SIGHASH_NONE,
+    SIGHASH_SINGLE,
+    SIGHASH_ANYONECANPAY,
+    SegwitV0SignatureHash,
+    TaprootSignatureHash,
+    is_op_success,
+    taproot_construct,
+)
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import assert_raises_rpc_error, assert_equal
+from test_framework.key import generate_privkey, compute_xonly_pubkey, sign_schnorr, tweak_add_privkey, ECKey
+from test_framework.address import (
+    hash160,
+    sha256,
+)
+from collections import namedtuple
+from io import BytesIO
+import random
+
+# === Framework for building spending transactions. ===
+#
+# The computation is represented as a "context" dict, whose entries store potentially-unevaluated expressions that
+# refer to lower-level ones. By overwriting these expression, many aspects - both high and low level - of the signing
+# process can be overridden.
+#
+# Specifically, a context object is a dict that maps names to compositions of:
+# - values
+# - lists of values
+# - callables which, when fed the context object as argument, produce any of these
+#
+# The DEFAULT_CONTEXT object specifies a standard signing process, with many overridable knobs.
+#
+# The get(ctx, name) function can evaluate a name, and cache its result in the context.
+# getter(name) can be used to construct a callable that evaluates name. For example:
+#
+#   ctx1 = {**DEFAULT_CONTEXT, inputs=[getter("sign"), b'\x01']}
+#
+# creates a context where the script inputs are a signature plus the bytes 0x01.
+#
+# override(expr, name1=expr1, name2=expr2, ...) can be used to cause an expression to be evaluated in a selectively
+# modified context. For example:
+#
+#   ctx2 = {**DEFAULT_CONTEXT, sighash=override(default_sighash, hashtype=SIGHASH_DEFAULT)}
+#
+# creates a context ctx2 where the sighash is modified to use hashtype=SIGHASH_DEFAULT. This differs from
+#
+#   ctx3 = {**DEFAULT_CONTEXT, hashtype=SIGHASH_DEFAULT}
+#
+# in that ctx3 will globally use hashtype=SIGHASH_DEFAULT (including in the hashtype byte appended to the signature)
+# while ctx2 only uses the modified hashtype inside the sighash calculation.
+
+def deep_eval(ctx, expr):
+    """Recursively replace any callables c in expr (including inside lists) with c(ctx)."""
+    while callable(expr):
+        expr = expr(ctx)
+    if isinstance(expr, list):
+        expr = [deep_eval(ctx, x) for x in expr]
+    return expr
+
+# Data type to represent fully-evaluated expressions in a context dict (so we can avoid reevaluating them).
+Final = namedtuple("Final", "value")
+
+def get(ctx, name):
+    """Evaluate name in context ctx."""
+    assert name in ctx, "Missing '%s' in context" % name
+    expr = ctx[name]
+    if not isinstance(expr, Final):
+        # Evaluate and cache the result.
+        expr = Final(deep_eval(ctx, expr))
+        ctx[name] = expr
+    return expr.value
+
+def getter(name):
+    """Return a callable that evaluates name in its passed context."""
+    return lambda ctx: get(ctx, name)
+
+def override(expr, **kwargs):
+    """Return a callable that evaluates expr in a modified context."""
+    return lambda ctx: deep_eval({**ctx, **kwargs}, expr)
+
+# === Implementations for the various default expressions in DEFAULT_CONTEXT ===
+
+def default_hashtype(ctx):
+    """Default expression for "hashtype": SIGHASH_DEFAULT for taproot, SIGHASH_ALL otherwise."""
+    mode = get(ctx, "mode")
+    if mode == "taproot":
+        return SIGHASH_DEFAULT
+    else:
+        return SIGHASH_ALL
+
+def default_tapleaf(ctx):
+    """Default expression for "tapleaf": looking up leaf in tap[2]."""
+    return get(ctx, "tap").leaves[get(ctx, "leaf")]
+
+def default_script_taproot(ctx):
+    """Default expression for "script_taproot": tapleaf.script."""
+    return get(ctx, "tapleaf").script
+
+def default_leafversion(ctx):
+    """Default expression for "leafversion": tapleaf.version"""
+    return get(ctx, "tapleaf").version
+
+def default_negflag(ctx):
+    """Default expression for "negflag": tap.negflag."""
+    return get(ctx, "tap").negflag
+
+def default_pubkey_inner(ctx):
+    """Default expression for "pubkey_inner": tap.inner_pubkey."""
+    return get(ctx, "tap").inner_pubkey
+
+def default_merklebranch(ctx):
+    """Default expression for "merklebranch": tapleaf.merklebranch."""
+    return get(ctx, "tapleaf").merklebranch
+
+def default_controlblock(ctx):
+    """Default expression for "controlblock": combine leafversion, negflag, pubkey_inner, merklebranch."""
+    return bytes([get(ctx, "leafversion") + get(ctx, "negflag")]) + get(ctx, "pubkey_inner") + get(ctx, "merklebranch")
+
+def default_sighash(ctx):
+    """Default expression for "sighash": depending on mode, compute BIP341, BIP143, or legacy sighash."""
+    tx = get(ctx, "tx")
+    idx = get(ctx, "idx")
+    hashtype = get(ctx, "hashtype_actual")
+    mode = get(ctx, "mode")
+    if mode == "taproot":
+        # BIP341 signature hash
+        utxos = get(ctx, "utxos")
+        annex = get(ctx, "annex")
+        if get(ctx, "leaf") is not None:
+            codeseppos = get(ctx, "codeseppos")
+            leaf_ver = get(ctx, "leafversion")
+            script = get(ctx, "script_taproot")
+            return TaprootSignatureHash(tx, utxos, hashtype, idx, scriptpath=True, script=script, leaf_ver=leaf_ver, codeseparator_pos=codeseppos, annex=annex)
+        else:
+            return TaprootSignatureHash(tx, utxos, hashtype, idx, scriptpath=False, annex=annex)
+    elif mode == "witv0":
+        # BIP143 signature hash
+        scriptcode = get(ctx, "scriptcode")
+        utxos = get(ctx, "utxos")
+        return SegwitV0SignatureHash(scriptcode, tx, idx, hashtype, utxos[idx].nValue)
+    else:
+        # Pre-segwit signature hash
+        scriptcode = get(ctx, "scriptcode")
+        return LegacySignatureHash(scriptcode, tx, idx, hashtype)[0]
+
+def default_tweak(ctx):
+    """Default expression for "tweak": None if a leaf is specified, tap[0] otherwise."""
+    if get(ctx, "leaf") is None:
+        return get(ctx, "tap").tweak
+    return None
+
+def default_key_tweaked(ctx):
+    """Default expression for "key_tweaked": key if tweak is None, tweaked with it otherwise."""
+    key = get(ctx, "key")
+    tweak = get(ctx, "tweak")
+    if tweak is None:
+        return key
+    else:
+        return tweak_add_privkey(key, tweak)
+
+def default_signature(ctx):
+    """Default expression for "signature": BIP340 signature or ECDSA signature depending on mode."""
+    sighash = get(ctx, "sighash")
+    if get(ctx, "mode") == "taproot":
+        key = get(ctx, "key_tweaked")
+        flip_r = get(ctx, "flag_flip_r")
+        flip_p = get(ctx, "flag_flip_p")
+        return sign_schnorr(key, sighash, flip_r=flip_r, flip_p=flip_p)
+    else:
+        key = get(ctx, "key")
+        return key.sign_ecdsa(sighash)
+
+def default_hashtype_actual(ctx):
+    """Default expression for "hashtype_actual": hashtype, unless mismatching SIGHASH_SINGLE in taproot."""
+    hashtype = get(ctx, "hashtype")
+    mode = get(ctx, "mode")
+    if mode != "taproot":
+        return hashtype
+    idx = get(ctx, "idx")
+    tx = get(ctx, "tx")
+    if hashtype & 3 == SIGHASH_SINGLE and idx >= len(tx.vout):
+        return (hashtype & ~3) | SIGHASH_NONE
+    return hashtype
+
+def default_bytes_hashtype(ctx):
+    """Default expression for "bytes_hashtype": bytes([hashtype_actual]) if not 0, b"" otherwise."""
+    return bytes([x for x in [get(ctx, "hashtype_actual")] if x != 0])
+
+def default_sign(ctx):
+    """Default expression for "sign": concatenation of signature and bytes_hashtype."""
+    return get(ctx, "signature") + get(ctx, "bytes_hashtype")
+
+def default_inputs_keypath(ctx):
+    """Default expression for "inputs_keypath": a signature."""
+    return [get(ctx, "sign")]
+
+def default_witness_taproot(ctx):
+    """Default expression for "witness_taproot", consisting of inputs, script, control block, and annex as needed."""
+    annex = get(ctx, "annex")
+    suffix_annex = []
+    if annex is not None:
+        suffix_annex = [annex]
+    if get(ctx, "leaf") is None:
+        return get(ctx, "inputs_keypath") + suffix_annex
+    else:
+        return get(ctx, "inputs") + [bytes(get(ctx, "script_taproot")), get(ctx, "controlblock")] + suffix_annex
+
+def default_witness_witv0(ctx):
+    """Default expression for "witness_witv0", consisting of inputs and witness script, as needed."""
+    script = get(ctx, "script_witv0")
+    inputs = get(ctx, "inputs")
+    if script is None:
+        return inputs
+    else:
+        return inputs + [script]
+
+def default_witness(ctx):
+    """Default expression for "witness", delegating to "witness_taproot" or "witness_witv0" as needed."""
+    mode = get(ctx, "mode")
+    if mode == "taproot":
+        return get(ctx, "witness_taproot")
+    elif mode == "witv0":
+        return get(ctx, "witness_witv0")
+    else:
+        return []
+
+def default_scriptsig(ctx):
+    """Default expression for "scriptsig", consisting of inputs and redeemscript, as needed."""
+    scriptsig = []
+    mode = get(ctx, "mode")
+    if mode == "legacy":
+        scriptsig = get(ctx, "inputs")
+    redeemscript = get(ctx, "script_p2sh")
+    if redeemscript is not None:
+        scriptsig += [bytes(redeemscript)]
+    return scriptsig
+
+# The default context object.
+DEFAULT_CONTEXT = {
+    # == The main expressions to evaluate. Only override these for unusual or invalid spends. ==
+    # The overall witness stack, as a list of bytes objects.
+    "witness": default_witness,
+    # The overall scriptsig, as a list of CScript objects (to be concatenated) and bytes objects (to be pushed)
+    "scriptsig": default_scriptsig,
+
+    # == Expressions you'll generally only override for intentionally invalid spends. ==
+    # The witness stack for spending a taproot output.
+    "witness_taproot": default_witness_taproot,
+    # The witness stack for spending a P2WPKH/P2WSH output.
+    "witness_witv0": default_witness_witv0,
+    # The script inputs for a taproot key path spend.
+    "inputs_keypath": default_inputs_keypath,
+    # The actual hashtype to use (usually equal to hashtype, but in taproot SIGHASH_SINGLE is not always allowed).
+    "hashtype_actual": default_hashtype_actual,
+    # The bytes object for a full signature (including hashtype byte, if needed).
+    "bytes_hashtype": default_bytes_hashtype,
+    # A full script signature (bytes including hashtype, if needed)
+    "sign": default_sign,
+    # An ECDSA or Schnorr signature (excluding hashtype byte).
+    "signature": default_signature,
+    # The 32-byte tweaked key (equal to key for script path spends, or key+tweak for key path spends).
+    "key_tweaked": default_key_tweaked,
+    # The tweak to use (None for script path spends, the actual tweak for key path spends).
+    "tweak": default_tweak,
+    # The sighash value (32 bytes)
+    "sighash": default_sighash,
+    # The information about the chosen script path spend (TaprootLeafInfo object).
+    "tapleaf": default_tapleaf,
+    # The script to push, and include in the sighash, for a taproot script path spend.
+    "script_taproot": default_script_taproot,
+    # The inner pubkey for a taproot script path spend (32 bytes).
+    "pubkey_inner": default_pubkey_inner,
+    # The negation flag of the inner pubkey for a taproot script path spend.
+    "negflag": default_negflag,
+    # The leaf version to include in the sighash (this does not affect the one in the control block).
+    "leafversion": default_leafversion,
+    # The Merkle path to include in the control block for a script path spend.
+    "merklebranch": default_merklebranch,
+    # The control block to push for a taproot script path spend.
+    "controlblock": default_controlblock,
+    # Whether to produce signatures with invalid P sign (Schnorr signatures only).
+    "flag_flip_p": False,
+    # Whether to produce signatures with invalid R sign (Schnorr signatures only).
+    "flag_flip_r": False,
+
+    # == Parameters that can be changed without invalidating, but do have a default: ==
+    # The hashtype (as an integer).
+    "hashtype": default_hashtype,
+    # The annex (only when mode=="taproot").
+    "annex": None,
+    # The codeseparator position (only when mode=="taproot").
+    "codeseppos": -1,
+    # The redeemscript to add to the scriptSig (if P2SH; None implies not P2SH).
+    "script_p2sh": None,
+    # The script to add to the witness in (if P2WSH; None implies P2WPKH)
+    "script_witv0": None,
+    # The leaf to use in taproot spends (if script path spend; None implies key path spend).
+    "leaf": None,
+    # The input arguments to provide to the executed script
+    "inputs": [],
+
+    # == Parameters to be set before evaluation: ==
+    # - mode: what spending style to use ("taproot", "witv0", or "legacy").
+    # - key: the (untweaked) private key to sign with (ECKey object for ECDSA, 32 bytes for Schnorr).
+    # - tap: the TaprootInfo object (see taproot_construct; needed in mode=="taproot").
+    # - tx: the transaction to sign.
+    # - utxos: the UTXOs being spent (needed in mode=="witv0" and mode=="taproot").
+    # - idx: the input position being signed.
+    # - scriptcode: the scriptcode to include in legacy and witv0 sighashes.
+}
+
+def flatten(lst):
+    ret = []
+    for elem in lst:
+        if isinstance(elem, list):
+            ret += flatten(elem)
+        else:
+            ret.append(elem)
+    return ret
+
+def spend(tx, idx, utxos, **kwargs):
+    """Sign transaction input idx of tx, provided utxos is the list of outputs being spent.
+
+    Additional arguments may be provided that override any aspect of the signing process.
+    See DEFAULT_CONTEXT above for what can be overridden, and what must be provided.
+    """
+
+    ctx = {**DEFAULT_CONTEXT, "tx":tx, "idx":idx, "utxos":utxos, **kwargs}
+
+    def to_script(elem):
+        """If fed a CScript, return it; if fed bytes, return a CScript that pushes it."""
+        if isinstance(elem, CScript):
+            return elem
+        else:
+            return CScript([elem])
+
+    scriptsig_list = flatten(get(ctx, "scriptsig"))
+    scriptsig = CScript(b"".join(bytes(to_script(elem)) for elem in scriptsig_list))
+    witness_stack = flatten(get(ctx, "witness"))
+    return (scriptsig, witness_stack)
+
+
+# === Spender objects ===
+#
+# Each spender is a tuple of:
+# - A scriptPubKey which is to be spent from (CScript)
+# - A comment describing the test (string)
+# - Whether the spending (on itself) is expected to be standard (bool)
+# - A tx-signing lambda returning (scriptsig, witness_stack), taking as inputs:
+#   - A transaction to sign (CTransaction)
+#   - An input position (int)
+#   - The spent UTXOs by this transaction (list of CTxOut)
+#   - Whether to produce a valid spend (bool)
+# - A string with an expected error message for failure case if known
+# - The (pre-taproot) sigops weight consumed by a successful spend
+# - Whether this spend cannot fail
+# - Whether this test demands being placed in a txin with no corresponding txout (for testing SIGHASH_SINGLE behavior)
+
+Spender = namedtuple("Spender", "script,comment,is_standard,sat_function,err_msg,sigops_weight,no_fail,need_vin_vout_mismatch")
+
+def make_spender(comment, *, tap=None, witv0=False, script=None, pkh=None, p2sh=False, spk_mutate_pre_p2sh=None, failure=None, standard=True, err_msg=None, sigops_weight=0, need_vin_vout_mismatch=False, **kwargs):
+    """Helper for constructing Spender objects using the context signing framework.
+
+    * tap: a TaprootInfo object (see taproot_construct), for Taproot spends (cannot be combined with pkh, witv0, or script)
+    * witv0: boolean indicating the use of witness v0 spending (needs one of script or pkh)
+    * script: the actual script executed (for bare/P2WSH/P2SH spending)
+    * pkh: the public key for P2PKH or P2WPKH spending
+    * p2sh: whether the output is P2SH wrapper (this is supported even for Taproot, where it makes the output unencumbered)
+    * spk_mutate_pre_psh: a callable to be applied to the script (before potentially P2SH-wrapping it)
+    * failure: a dict of entries to override in the context when intentionally failing to spend (if None, no_fail will be set)
+    * standard: whether the (valid version of) spending is expected to be standard
+    * err_msg: a string with an expected error message for failure (or None, if not cared about)
+    * sigops_weight: the pre-taproot sigops weight consumed by a successful spend
+    """
+
+    conf = dict()
+
+    # Compute scriptPubKey and set useful defaults based on the inputs.
+    if witv0:
+        assert tap is None
+        conf["mode"] = "witv0"
+        if pkh is not None:
+            # P2WPKH
+            assert script is None
+            pubkeyhash = hash160(pkh)
+            spk = CScript([OP_0, pubkeyhash])
+            conf["scriptcode"] = CScript([OP_DUP, OP_HASH160, pubkeyhash, OP_EQUALVERIFY, OP_CHECKSIG])
+            conf["script_witv0"] = None
+            conf["inputs"] = [getter("sign"), pkh]
+        elif script is not None:
+            # P2WSH
+            spk = CScript([OP_0, sha256(script)])
+            conf["scriptcode"] = script
+            conf["script_witv0"] = script
+        else:
+            assert False
+    elif tap is None:
+        conf["mode"] = "legacy"
+        if pkh is not None:
+            # P2PKH
+            assert script is None
+            pubkeyhash = hash160(pkh)
+            spk = CScript([OP_DUP, OP_HASH160, pubkeyhash, OP_EQUALVERIFY, OP_CHECKSIG])
+            conf["scriptcode"] = spk
+            conf["inputs"] = [getter("sign"), pkh]
+        elif script is not None:
+            # bare
+            spk = script
+            conf["scriptcode"] = script
+        else:
+            assert False
+    else:
+        assert script is None
+        conf["mode"] = "taproot"
+        conf["tap"] = tap
+        spk = tap.scriptPubKey
+
+    if spk_mutate_pre_p2sh is not None:
+        spk = spk_mutate_pre_p2sh(spk)
+
+    if p2sh:
+        # P2SH wrapper can be combined with anything else
+        conf["script_p2sh"] = spk
+        spk = CScript([OP_HASH160, hash160(spk), OP_EQUAL])
+
+    conf = {**conf, **kwargs}
+
+    def sat_fn(tx, idx, utxos, valid):
+        if valid:
+            return spend(tx, idx, utxos, **conf)
+        else:
+            assert failure is not None
+            return spend(tx, idx, utxos, **{**conf, **failure})
+
+    return Spender(script=spk, comment=comment, is_standard=standard, sat_function=sat_fn, err_msg=err_msg, sigops_weight=sigops_weight, no_fail=failure is None, need_vin_vout_mismatch=need_vin_vout_mismatch)
+
+def add_spender(spenders, *args, **kwargs):
+    """Make a spender using make_spender, and add it to spenders."""
+    spenders.append(make_spender(*args, **kwargs))
+
+# === Helpers for the test ===
+
+def random_checksig_style(pubkey):
+    """Creates a random CHECKSIG* tapscript that would succeed with only the valid signature on witness stack."""
+    return bytes(CScript([pubkey, OP_CHECKSIG]))
+    opcode = random.choice([OP_CHECKSIG, OP_CHECKSIGVERIFY, OP_CHECKSIGADD])
+    if (opcode == OP_CHECKSIGVERIFY):
+        ret = CScript([pubkey, opcode, OP_1])
+    elif (opcode == OP_CHECKSIGADD):
+        num = random.choice([0, 0x7fffffff, -0x7fffffff])
+        ret = CScript([num, pubkey, opcode, num + 1, OP_EQUAL])
+    else:
+        ret = CScript([pubkey, opcode])
+    return bytes(ret)
+
+def random_bytes(n):
+    """Return a random bytes object of length n."""
+    return bytes(random.getrandbits(8) for i in range(n))
+
+def bitflipper(expr):
+    """Return a callable that evaluates expr and returns it with a random bitflip."""
+    def fn(ctx):
+        sub = deep_eval(ctx, expr)
+        assert isinstance(sub, bytes)
+        return (int.from_bytes(sub, 'little') ^ (1 << random.randrange(len(sub) * 8))).to_bytes(len(sub), 'little')
+    return fn
+
+def zero_appender(expr):
+    """Return a callable that evaluates expr and returns it with a zero added."""
+    return lambda ctx: deep_eval(ctx, expr) + b"\x00"
+
+def byte_popper(expr):
+    """Return a callable that evaluates expr and returns it with its last byte removed."""
+    return lambda ctx: deep_eval(ctx, expr)[:-1]
+
+# Expected error strings
+
+ERR_SIG_SIZE = {"err_msg": "Invalid Schnorr signature size"}
+ERR_SIG_HASHTYPE = {"err_msg": "Invalid Schnorr signature hash type"}
+ERR_SIG_SCHNORR = {"err_msg": "Invalid Schnorr signature"}
+ERR_OP_RETURN = {"err_msg": "OP_RETURN was encountered"}
+ERR_CONTROLBLOCK_SIZE = {"err_msg": "Invalid Taproot control block size"}
+ERR_WITNESS_PROGRAM_MISMATCH = {"err_msg": "Witness program hash mismatch"}
+ERR_PUSH_LIMIT = {"err_msg": "Push value size limit exceeded"}
+ERR_DISABLED_OPCODE = {"err_msg": "Attempted to use a disabled opcode"}
+ERR_TAPSCRIPT_CHECKMULTISIG = {"err_msg": "OP_CHECKMULTISIG(VERIFY) is not available in tapscript"}
+ERR_MINIMALIF = {"err_msg": "OP_IF/NOTIF argument must be minimal in tapscript"}
+ERR_UNKNOWN_PUBKEY = {"err_msg": "Public key is neither compressed or uncompressed"}
+ERR_STACK_SIZE = {"err_msg": "Stack size limit exceeded"}
+ERR_CLEANSTACK = {"err_msg": "Stack size must be exactly one after execution"}
+ERR_STACK_EMPTY = {"err_msg": "Operation not valid with the current stack size"}
+ERR_SIGOPS_RATIO = {"err_msg": "Too much signature validation relative to witness weight"}
+ERR_UNDECODABLE = {"err_msg": "Opcode missing or not understood"}
+ERR_NO_SUCCESS = {"err_msg": "Script evaluated without error but finished with a false/empty top stack element"}
+ERR_EMPTY_WITNESS = {"err_msg": "Witness program was passed an empty witness"}
+ERR_CHECKSIGVERIFY = {"err_msg": "Script failed an OP_CHECKSIGVERIFY operation"}
+
+VALID_SIGHASHES_ECDSA = [
+    SIGHASH_ALL,
+    SIGHASH_NONE,
+    SIGHASH_SINGLE,
+    SIGHASH_ANYONECANPAY + SIGHASH_ALL,
+    SIGHASH_ANYONECANPAY + SIGHASH_NONE,
+    SIGHASH_ANYONECANPAY + SIGHASH_SINGLE
+]
+
+VALID_SIGHASHES_TAPROOT = [SIGHASH_DEFAULT] + VALID_SIGHASHES_ECDSA
+
+VALID_SIGHASHES_TAPROOT_SINGLE = [
+    SIGHASH_SINGLE,
+    SIGHASH_ANYONECANPAY + SIGHASH_SINGLE
+]
+
+VALID_SIGHASHES_TAPROOT_NO_SINGLE = [h for h in VALID_SIGHASHES_TAPROOT if h not in VALID_SIGHASHES_TAPROOT_SINGLE]
+
+SIGHASH_BITFLIP = {"failure": {"sighash": bitflipper(default_sighash)}}
+SIG_POP_BYTE = {"failure": {"sign": byte_popper(default_sign)}}
+SINGLE_SIG = {"inputs": [getter("sign")]}
+SIG_ADD_ZERO = {"failure": {"sign": zero_appender(default_sign)}}
+
+DUST_LIMIT = 600
+MIN_FEE = 50000
+
+# === Actual test cases ===
+
+
+def spenders_taproot_active():
+    """Return a list of Spenders for testing post-Taproot activation behavior."""
+
+    secs = [generate_privkey() for _ in range(8)]
+    pubs = [compute_xonly_pubkey(sec)[0] for sec in secs]
+
+    spenders = []
+
+    # == Tests for BIP340 signature validation. ==
+    # These are primarily tested through the test vectors implemented in libsecp256k1, and in src/tests/key_tests.cpp.
+    # Some things are tested programmatically as well here.
+
+    tap = taproot_construct(pubs[0])
+    # Test with key with bit flipped.
+    add_spender(spenders, "sig/key", tap=tap, key=secs[0], failure={"key_tweaked": bitflipper(default_key_tweaked)}, **ERR_SIG_SCHNORR)
+    # Test with sighash with bit flipped.
+    add_spender(spenders, "sig/sighash", tap=tap, key=secs[0], failure={"sighash": bitflipper(default_sighash)}, **ERR_SIG_SCHNORR)
+    # Test with invalid R sign.
+    add_spender(spenders, "sig/flip_r", tap=tap, key=secs[0], failure={"flag_flip_r": True}, **ERR_SIG_SCHNORR)
+    # Test with invalid P sign.
+    add_spender(spenders, "sig/flip_p", tap=tap, key=secs[0], failure={"flag_flip_p": True}, **ERR_SIG_SCHNORR)
+    # Test with signature with bit flipped.
+    add_spender(spenders, "sig/bitflip", tap=tap, key=secs[0], failure={"signature": bitflipper(default_signature)}, **ERR_SIG_SCHNORR)
+
+    # == Tests for signature hashing ==
+
+    # Run all tests once with no annex, and once with a valid random annex.
+    for annex in [None, lambda _: bytes([ANNEX_TAG]) + random_bytes(random.randrange(0, 250))]:
+        # Non-empty annex is non-standard
+        no_annex = annex is None
+
+        # Sighash mutation tests (test all sighash combinations)
+        for hashtype in VALID_SIGHASHES_TAPROOT:
+            common = {"annex": annex, "hashtype": hashtype, "standard": no_annex}
+
+            # Pure pubkey
+            tap = taproot_construct(pubs[0])
+            add_spender(spenders, "sighash/purepk", tap=tap, key=secs[0], **common, **SIGHASH_BITFLIP, **ERR_SIG_SCHNORR)
+
+            # Pubkey/P2PK script combination
+            scripts = [("s0", CScript(random_checksig_style(pubs[1])))]
+            tap = taproot_construct(pubs[0], scripts)
+            add_spender(spenders, "sighash/keypath_hashtype_%x" % hashtype, tap=tap, key=secs[0], **common, **SIGHASH_BITFLIP, **ERR_SIG_SCHNORR)
+            add_spender(spenders, "sighash/scriptpath_hashtype_%x" % hashtype, tap=tap, leaf="s0", key=secs[1], **common, **SINGLE_SIG, **SIGHASH_BITFLIP, **ERR_SIG_SCHNORR)
+
+            # Test SIGHASH_SINGLE behavior in combination with mismatching outputs
+            if hashtype in VALID_SIGHASHES_TAPROOT_SINGLE:
+                add_spender(spenders, "sighash/keypath_hashtype_mis_%x" % hashtype, tap=tap, key=secs[0], annex=annex, standard=no_annex, hashtype_actual=random.choice(VALID_SIGHASHES_TAPROOT_NO_SINGLE), failure={"hashtype_actual": hashtype}, **ERR_SIG_HASHTYPE, need_vin_vout_mismatch=True)
+                add_spender(spenders, "sighash/scriptpath_hashtype_mis_%x" % hashtype, tap=tap, leaf="s0", key=secs[1], annex=annex, standard=no_annex, hashtype_actual=random.choice(VALID_SIGHASHES_TAPROOT_NO_SINGLE), **SINGLE_SIG, failure={"hashtype_actual": hashtype}, **ERR_SIG_HASHTYPE, need_vin_vout_mismatch=True)
+
+        # Test OP_CODESEPARATOR impact on sighashing.
+        hashtype = lambda _: random.choice(VALID_SIGHASHES_TAPROOT)
+        common = {"annex": annex, "hashtype": hashtype, "standard": no_annex}
+        scripts = [
+            ("pk_codesep", CScript(random_checksig_style(pubs[1]) + bytes([OP_CODESEPARATOR]))),  # codesep after checksig
+            ("codesep_pk", CScript(bytes([OP_CODESEPARATOR]) + random_checksig_style(pubs[1]))),  # codesep before checksig
+            ("branched_codesep", CScript([random_bytes(random.randrange(511)), OP_DROP, OP_IF, OP_CODESEPARATOR, pubs[0], OP_ELSE, OP_CODESEPARATOR, pubs[1], OP_ENDIF, OP_CHECKSIG])),  # branch dependent codesep
+        ]
+        random.shuffle(scripts)
+        tap = taproot_construct(pubs[0], scripts)
+        add_spender(spenders, "sighash/pk_codesep", tap=tap, leaf="pk_codesep", key=secs[1], **common, **SINGLE_SIG, **SIGHASH_BITFLIP, **ERR_SIG_SCHNORR)
+        add_spender(spenders, "sighash/codesep_pk", tap=tap, leaf="codesep_pk", key=secs[1], codeseppos=0, **common, **SINGLE_SIG, **SIGHASH_BITFLIP, **ERR_SIG_SCHNORR)
+        add_spender(spenders, "sighash/branched_codesep/left", tap=tap, leaf="branched_codesep", key=secs[0], codeseppos=3, **common, inputs=[getter("sign"), b'\x01'], **SIGHASH_BITFLIP, **ERR_SIG_SCHNORR)
+        add_spender(spenders, "sighash/branched_codesep/right", tap=tap, leaf="branched_codesep", key=secs[1], codeseppos=6, **common, inputs=[getter("sign"), b''], **SIGHASH_BITFLIP, **ERR_SIG_SCHNORR)
+
+    # Reusing the scripts above, test that various features affect the sighash.
+    add_spender(spenders, "sighash/annex", tap=tap, leaf="pk_codesep", key=secs[1], hashtype=hashtype, standard=False, **SINGLE_SIG, annex=bytes([ANNEX_TAG]), failure={"sighash": override(default_sighash, annex=None)}, **ERR_SIG_SCHNORR)
+    add_spender(spenders, "sighash/script", tap=tap, leaf="pk_codesep", key=secs[1], **common, **SINGLE_SIG, failure={"sighash": override(default_sighash, script_taproot=tap.leaves["codesep_pk"].script)}, **ERR_SIG_SCHNORR)
+    add_spender(spenders, "sighash/leafver", tap=tap, leaf="pk_codesep", key=secs[1], **common, **SINGLE_SIG, failure={"sighash": override(default_sighash, leafversion=random.choice([x & 0xFE for x in range(0x100) if x & 0xFE != 0xC0]))}, **ERR_SIG_SCHNORR)
+    add_spender(spenders, "sighash/scriptpath", tap=tap, leaf="pk_codesep", key=secs[1], **common, **SINGLE_SIG, failure={"sighash": override(default_sighash, leaf=None)}, **ERR_SIG_SCHNORR)
+    add_spender(spenders, "sighash/keypath", tap=tap, key=secs[0], **common, failure={"sighash": override(default_sighash, leaf="pk_codesep")}, **ERR_SIG_SCHNORR)
+
+    # Test that invalid hashtypes don't work, both in key path and script path spends
+    hashtype = lambda _: random.choice(VALID_SIGHASHES_TAPROOT)
+    for invalid_hashtype in [x for x in range(0x100) if x not in VALID_SIGHASHES_TAPROOT]:
+        add_spender(spenders, "sighash/keypath_unk_hashtype_%x" % invalid_hashtype, tap=tap, key=secs[0], hashtype=hashtype, failure={"hashtype": invalid_hashtype}, **ERR_SIG_HASHTYPE)
+        add_spender(spenders, "sighash/scriptpath_unk_hashtype_%x" % invalid_hashtype, tap=tap, leaf="pk_codesep", key=secs[1], **SINGLE_SIG, hashtype=hashtype, failure={"hashtype": invalid_hashtype}, **ERR_SIG_HASHTYPE)
+
+    # Test that hashtype 0 cannot have a hashtype byte, and 1 must have one.
+    add_spender(spenders, "sighash/hashtype0_byte_keypath", tap=tap, key=secs[0], hashtype=SIGHASH_DEFAULT, failure={"bytes_hashtype": bytes([SIGHASH_DEFAULT])}, **ERR_SIG_HASHTYPE)
+    add_spender(spenders, "sighash/hashtype0_byte_scriptpath", tap=tap, leaf="pk_codesep", key=secs[1], **SINGLE_SIG, hashtype=SIGHASH_DEFAULT, failure={"bytes_hashtype": bytes([SIGHASH_DEFAULT])}, **ERR_SIG_HASHTYPE)
+    add_spender(spenders, "sighash/hashtype1_byte_keypath", tap=tap, key=secs[0], hashtype=SIGHASH_ALL, failure={"bytes_hashtype": b''}, **ERR_SIG_SCHNORR)
+    add_spender(spenders, "sighash/hashtype1_byte_scriptpath", tap=tap, leaf="pk_codesep", key=secs[1], **SINGLE_SIG, hashtype=SIGHASH_ALL, failure={"bytes_hashtype": b''}, **ERR_SIG_SCHNORR)
+    # Test that hashtype 0 and hashtype 1 cannot be transmuted into each other.
+    add_spender(spenders, "sighash/hashtype0to1_keypath", tap=tap, key=secs[0], hashtype=SIGHASH_DEFAULT, failure={"bytes_hashtype": bytes([SIGHASH_ALL])}, **ERR_SIG_SCHNORR)
+    add_spender(spenders, "sighash/hashtype0to1_scriptpath", tap=tap, leaf="pk_codesep", key=secs[1], **SINGLE_SIG, hashtype=SIGHASH_DEFAULT, failure={"bytes_hashtype": bytes([SIGHASH_ALL])}, **ERR_SIG_SCHNORR)
+    add_spender(spenders, "sighash/hashtype1to0_keypath", tap=tap, key=secs[0], hashtype=SIGHASH_ALL, failure={"bytes_hashtype": b''}, **ERR_SIG_SCHNORR)
+    add_spender(spenders, "sighash/hashtype1to0_scriptpath", tap=tap, leaf="pk_codesep", key=secs[1], **SINGLE_SIG, hashtype=SIGHASH_ALL, failure={"bytes_hashtype": b''}, **ERR_SIG_SCHNORR)
+
+    # Test aspects of signatures with unusual lengths
+    for hashtype in [SIGHASH_DEFAULT, random.choice(VALID_SIGHASHES_TAPROOT)]:
+        scripts = [
+            ("csv", CScript([pubs[2], OP_CHECKSIGVERIFY, OP_1])),
+            ("cs_pos", CScript([pubs[2], OP_CHECKSIG])),
+            ("csa_pos", CScript([OP_0, pubs[2], OP_CHECKSIGADD, OP_1, OP_EQUAL])),
+            ("cs_neg", CScript([pubs[2], OP_CHECKSIG, OP_NOT])),
+            ("csa_neg", CScript([OP_2, pubs[2], OP_CHECKSIGADD, OP_2, OP_EQUAL]))
+        ]
+        random.shuffle(scripts)
+        tap = taproot_construct(pubs[3], scripts)
+        # Empty signatures
+        add_spender(spenders, "siglen/empty_keypath", tap=tap, key=secs[3], hashtype=hashtype, failure={"sign": b""}, **ERR_SIG_SIZE)
+        add_spender(spenders, "siglen/empty_csv", tap=tap, key=secs[2], leaf="csv", hashtype=hashtype, **SINGLE_SIG, failure={"sign": b""}, **ERR_CHECKSIGVERIFY)
+        add_spender(spenders, "siglen/empty_cs", tap=tap, key=secs[2], leaf="cs_pos", hashtype=hashtype, **SINGLE_SIG, failure={"sign": b""}, **ERR_NO_SUCCESS)
+        add_spender(spenders, "siglen/empty_csa", tap=tap, key=secs[2], leaf="csa_pos", hashtype=hashtype, **SINGLE_SIG, failure={"sign": b""}, **ERR_NO_SUCCESS)
+        add_spender(spenders, "siglen/empty_cs_neg", tap=tap, key=secs[2], leaf="cs_neg", hashtype=hashtype, **SINGLE_SIG, sign=b"", failure={"sign": lambda _: random_bytes(random.randrange(1, 63))}, **ERR_SIG_SIZE)
+        add_spender(spenders, "siglen/empty_csa_neg", tap=tap, key=secs[2], leaf="csa_neg", hashtype=hashtype, **SINGLE_SIG, sign=b"", failure={"sign": lambda _: random_bytes(random.randrange(66, 100))}, **ERR_SIG_SIZE)
+        # Appending a zero byte to signatures invalidates them
+        add_spender(spenders, "siglen/padzero_keypath", tap=tap, key=secs[3], hashtype=hashtype, **SIG_ADD_ZERO, **(ERR_SIG_HASHTYPE if hashtype == SIGHASH_DEFAULT else ERR_SIG_SIZE))
+        add_spender(spenders, "siglen/padzero_csv", tap=tap, key=secs[2], leaf="csv", hashtype=hashtype, **SINGLE_SIG, **SIG_ADD_ZERO, **(ERR_SIG_HASHTYPE if hashtype == SIGHASH_DEFAULT else ERR_SIG_SIZE))
+        add_spender(spenders, "siglen/padzero_cs", tap=tap, key=secs[2], leaf="cs_pos", hashtype=hashtype, **SINGLE_SIG, **SIG_ADD_ZERO, **(ERR_SIG_HASHTYPE if hashtype == SIGHASH_DEFAULT else ERR_SIG_SIZE))
+        add_spender(spenders, "siglen/padzero_csa", tap=tap, key=secs[2], leaf="csa_pos", hashtype=hashtype, **SINGLE_SIG, **SIG_ADD_ZERO, **(ERR_SIG_HASHTYPE if hashtype == SIGHASH_DEFAULT else ERR_SIG_SIZE))
+        add_spender(spenders, "siglen/padzero_cs_neg", tap=tap, key=secs[2], leaf="cs_neg", hashtype=hashtype, **SINGLE_SIG, sign=b"", **SIG_ADD_ZERO, **(ERR_SIG_HASHTYPE if hashtype == SIGHASH_DEFAULT else ERR_SIG_SIZE))
+        add_spender(spenders, "siglen/padzero_csa_neg", tap=tap, key=secs[2], leaf="csa_neg", hashtype=hashtype, **SINGLE_SIG, sign=b"", **SIG_ADD_ZERO, **(ERR_SIG_HASHTYPE if hashtype == SIGHASH_DEFAULT else ERR_SIG_SIZE))
+        # Removing the last byte from signatures invalidates them
+        add_spender(spenders, "siglen/popbyte_keypath", tap=tap, key=secs[3], hashtype=hashtype, **SIG_POP_BYTE, **(ERR_SIG_SIZE if hashtype == SIGHASH_DEFAULT else ERR_SIG_SCHNORR))
+        add_spender(spenders, "siglen/popbyte_csv", tap=tap, key=secs[2], leaf="csv", hashtype=hashtype, **SINGLE_SIG, **SIG_POP_BYTE, **(ERR_SIG_SIZE if hashtype == SIGHASH_DEFAULT else ERR_SIG_SCHNORR))
+        add_spender(spenders, "siglen/popbyte_cs", tap=tap, key=secs[2], leaf="cs_pos", hashtype=hashtype, **SINGLE_SIG, **SIG_POP_BYTE, **(ERR_SIG_SIZE if hashtype == SIGHASH_DEFAULT else ERR_SIG_SCHNORR))
+        add_spender(spenders, "siglen/popbyte_csa", tap=tap, key=secs[2], leaf="csa_pos", hashtype=hashtype, **SINGLE_SIG, **SIG_POP_BYTE, **(ERR_SIG_SIZE if hashtype == SIGHASH_DEFAULT else ERR_SIG_SCHNORR))
+        add_spender(spenders, "siglen/popbyte_cs_neg", tap=tap, key=secs[2], leaf="cs_neg", hashtype=hashtype, **SINGLE_SIG, sign=b"", **SIG_POP_BYTE, **(ERR_SIG_SIZE if hashtype == SIGHASH_DEFAULT else ERR_SIG_SCHNORR))
+        add_spender(spenders, "siglen/popbyte_csa_neg", tap=tap, key=secs[2], leaf="csa_neg", hashtype=hashtype, **SINGLE_SIG, sign=b"", **SIG_POP_BYTE, **(ERR_SIG_SIZE if hashtype == SIGHASH_DEFAULT else ERR_SIG_SCHNORR))
+        # Verify that an invalid signature is not allowed, not even when the CHECKSIG* is expected to fail.
+        add_spender(spenders, "siglen/invalid_cs_neg", tap=tap, key=secs[2], leaf="cs_neg", hashtype=hashtype, **SINGLE_SIG, sign=b"", failure={"sign": default_sign, "sighash": bitflipper(default_sighash)}, **ERR_SIG_SCHNORR)
+        add_spender(spenders, "siglen/invalid_csa_neg", tap=tap, key=secs[2], leaf="csa_neg", hashtype=hashtype, **SINGLE_SIG, sign=b"", failure={"sign": default_sign, "sighash": bitflipper(default_sighash)}, **ERR_SIG_SCHNORR)
+
+    # == Test that BIP341 spending only applies to witness version 1, program length 32, no P2SH ==
+
+    for p2sh in [False, True]:
+        for witver in range(1, 17):
+            for witlen in [20, 31, 32, 33]:
+                def mutate(spk):
+                    prog = spk[2:]
+                    assert len(prog) == 32
+                    if witlen < 32:
+                        prog = prog[0:witlen]
+                    elif witlen > 32:
+                        prog += bytes([0 for _ in range(witlen - 32)])
+                    return CScript([CScriptOp.encode_op_n(witver), prog])
+                scripts = [("s0", CScript([pubs[0], OP_CHECKSIG])), ("dummy", CScript([OP_RETURN]))]
+                tap = taproot_construct(pubs[1], scripts)
+                if not p2sh and witver == 1 and witlen == 32:
+                    add_spender(spenders, "applic/keypath", p2sh=p2sh, spk_mutate_pre_p2sh=mutate, tap=tap, key=secs[1], **SIGHASH_BITFLIP, **ERR_SIG_SCHNORR)
+                    add_spender(spenders, "applic/scriptpath", p2sh=p2sh, leaf="s0", spk_mutate_pre_p2sh=mutate, tap=tap, key=secs[0], **SINGLE_SIG, failure={"leaf": "dummy"}, **ERR_OP_RETURN)
+                else:
+                    add_spender(spenders, "applic/keypath", p2sh=p2sh, spk_mutate_pre_p2sh=mutate, tap=tap, key=secs[1], standard=False)
+                    add_spender(spenders, "applic/scriptpath", p2sh=p2sh, leaf="s0", spk_mutate_pre_p2sh=mutate, tap=tap, key=secs[0], **SINGLE_SIG, standard=False)
+
+    # == Test various aspects of BIP341 spending paths ==
+
+    # A set of functions that compute the hashing partner in a Merkle tree, designed to exercise
+    # edge cases. This relies on the taproot_construct feature that a lambda can be passed in
+    # instead of a subtree, to compute the partner to be hashed with.
+    PARTNER_MERKLE_FN = [
+        # Combine with itself
+        lambda h: h,
+        # Combine with hash 0
+        lambda h: bytes([0 for _ in range(32)]),
+        # Combine with hash 2^256-1
+        lambda h: bytes([0xff for _ in range(32)]),
+        # Combine with itself-1 (BE)
+        lambda h: (int.from_bytes(h, 'big') - 1).to_bytes(32, 'big'),
+        # Combine with itself+1 (BE)
+        lambda h: (int.from_bytes(h, 'big') + 1).to_bytes(32, 'big'),
+        # Combine with itself-1 (LE)
+        lambda h: (int.from_bytes(h, 'little') - 1).to_bytes(32, 'big'),
+        # Combine with itself+1 (LE)
+        lambda h: (int.from_bytes(h, 'little') + 1).to_bytes(32, 'little'),
+        # Combine with random bitflipped version of self.
+        lambda h: (int.from_bytes(h, 'little') ^ (1 << random.randrange(256))).to_bytes(32, 'little')
+    ]
+    # Start with a tree of that has depth 1 for "128deep" and depth 2 for "129deep".
+    scripts = [("128deep", CScript([pubs[0], OP_CHECKSIG])), [("129deep", CScript([pubs[0], OP_CHECKSIG])), random.choice(PARTNER_MERKLE_FN)]]
+    # Add 127 nodes on top of that tree, so that "128deep" and "129deep" end up at their designated depths.
+    for _ in range(127):
+        scripts = [scripts, random.choice(PARTNER_MERKLE_FN)]
+    tap = taproot_construct(pubs[0], scripts)
+    # Test that spends with a depth of 128 work, but 129 doesn't (even with a tree with weird Merkle branches in it).
+    add_spender(spenders, "spendpath/merklelimit", tap=tap, leaf="128deep", **SINGLE_SIG, key=secs[0], failure={"leaf": "129deep"}, **ERR_CONTROLBLOCK_SIZE)
+    # Test that flipping the negation bit invalidates spends.
+    add_spender(spenders, "spendpath/negflag", tap=tap, leaf="128deep", **SINGLE_SIG, key=secs[0], failure={"negflag": lambda ctx: 1 - default_negflag(ctx)}, **ERR_WITNESS_PROGRAM_MISMATCH)
+    # Test that bitflips in the Merkle branch invalidate it.
+    add_spender(spenders, "spendpath/bitflipmerkle", tap=tap, leaf="128deep", **SINGLE_SIG, key=secs[0], failure={"merklebranch": bitflipper(default_merklebranch)}, **ERR_WITNESS_PROGRAM_MISMATCH)
+    # Test that bitflips in the inner pubkey invalidate it.
+    add_spender(spenders, "spendpath/bitflippubkey", tap=tap, leaf="128deep", **SINGLE_SIG, key=secs[0], failure={"pubkey_inner": bitflipper(default_pubkey_inner)}, **ERR_WITNESS_PROGRAM_MISMATCH)
+    # Test that empty witnesses are invalid.
+    add_spender(spenders, "spendpath/emptywit", tap=tap, leaf="128deep", **SINGLE_SIG, key=secs[0], failure={"witness": []}, **ERR_EMPTY_WITNESS)
+    # Test that adding garbage to the control block invalidates it.
+    add_spender(spenders, "spendpath/padlongcontrol", tap=tap, leaf="128deep", **SINGLE_SIG, key=secs[0], failure={"controlblock": lambda ctx: default_controlblock(ctx) + random_bytes(random.randrange(1, 32))}, **ERR_CONTROLBLOCK_SIZE)
+    # Test that truncating the control block invalidates it.
+    add_spender(spenders, "spendpath/trunclongcontrol", tap=tap, leaf="128deep", **SINGLE_SIG, key=secs[0], failure={"controlblock": lambda ctx: default_merklebranch(ctx)[0:random.randrange(1, 32)]}, **ERR_CONTROLBLOCK_SIZE)
+
+    scripts = [("s", CScript([pubs[0], OP_CHECKSIG]))]
+    tap = taproot_construct(pubs[1], scripts)
+    # Test that adding garbage to the control block invalidates it.
+    add_spender(spenders, "spendpath/padshortcontrol", tap=tap, leaf="s", **SINGLE_SIG, key=secs[0], failure={"controlblock": lambda ctx: default_controlblock(ctx) + random_bytes(random.randrange(1, 32))}, **ERR_CONTROLBLOCK_SIZE)
+    # Test that truncating the control block invalidates it.
+    add_spender(spenders, "spendpath/truncshortcontrol", tap=tap, leaf="s", **SINGLE_SIG, key=secs[0], failure={"controlblock": lambda ctx: default_merklebranch(ctx)[0:random.randrange(1, 32)]}, **ERR_CONTROLBLOCK_SIZE)
+    # Test that truncating the control block to 1 byte ("-1 Merkle length") invalidates it
+    add_spender(spenders, "spendpath/trunc1shortcontrol", tap=tap, leaf="s", **SINGLE_SIG, key=secs[0], failure={"controlblock": lambda ctx: default_merklebranch(ctx)[0:1]}, **ERR_CONTROLBLOCK_SIZE)
+
+    # == Test BIP342 edge cases ==
+
+    csa_low_val = random.randrange(0, 17) # Within range for OP_n
+    csa_low_result = csa_low_val + 1
+
+    csa_high_val = random.randrange(17, 100) if random.getrandbits(1) else random.randrange(-100, -1) # Outside OP_n range
+    csa_high_result = csa_high_val + 1
+
+    OVERSIZE_NUMBER = 2**31
+    assert_equal(len(CScriptNum.encode(CScriptNum(OVERSIZE_NUMBER))), 6)
+    assert_equal(len(CScriptNum.encode(CScriptNum(OVERSIZE_NUMBER-1))), 5)
+
+    big_choices = []
+    big_scriptops = []
+    for i in range(1000):
+        r = random.randrange(len(pubs))
+        big_choices.append(r)
+        big_scriptops += [pubs[r], OP_CHECKSIGVERIFY]
+
+
+    def big_spend_inputs(ctx):
+        """Helper function to construct the script input for t33/t34 below."""
+        # Instead of signing 999 times, precompute signatures for every (key, hashtype) combination
+        sigs = {}
+        for ht in VALID_SIGHASHES_TAPROOT:
+            for k in range(len(pubs)):
+                sigs[(k, ht)] = override(default_sign, hashtype=ht, key=secs[k])(ctx)
+        num = get(ctx, "num")
+        return [sigs[(big_choices[i], random.choice(VALID_SIGHASHES_TAPROOT))] for i in range(num - 1, -1, -1)]
+
+    # Various BIP342 features
+    scripts = [
+        # 0) drop stack element and OP_CHECKSIG
+        ("t0", CScript([OP_DROP, pubs[1], OP_CHECKSIG])),
+        # 1) normal OP_CHECKSIG
+        ("t1", CScript([pubs[1], OP_CHECKSIG])),
+        # 2) normal OP_CHECKSIGVERIFY
+        ("t2", CScript([pubs[1], OP_CHECKSIGVERIFY, OP_1])),
+        # 3) Hypothetical OP_CHECKMULTISIG script that takes a single sig as input
+        ("t3", CScript([OP_0, OP_SWAP, OP_1, pubs[1], OP_1, OP_CHECKMULTISIG])),
+        # 4) Hypothetical OP_CHECKMULTISIGVERIFY script that takes a single sig as input
+        ("t4", CScript([OP_0, OP_SWAP, OP_1, pubs[1], OP_1, OP_CHECKMULTISIGVERIFY, OP_1])),
+        # 5) OP_IF script that needs a true input
+        ("t5", CScript([OP_IF, pubs[1], OP_CHECKSIG, OP_ELSE, OP_RETURN, OP_ENDIF])),
+        # 6) OP_NOTIF script that needs a true input
+        ("t6", CScript([OP_NOTIF, OP_RETURN, OP_ELSE, pubs[1], OP_CHECKSIG, OP_ENDIF])),
+        # 7) OP_CHECKSIG with an empty key
+        ("t7", CScript([OP_0, OP_CHECKSIG])),
+        # 8) OP_CHECKSIGVERIFY with an empty key
+        ("t8", CScript([OP_0, OP_CHECKSIGVERIFY, OP_1])),
+        # 9) normal OP_CHECKSIGADD that also ensures return value is correct
+        ("t9", CScript([csa_low_val, pubs[1], OP_CHECKSIGADD, csa_low_result, OP_EQUAL])),
+        # 10) OP_CHECKSIGADD with empty key
+        ("t10", CScript([csa_low_val, OP_0, OP_CHECKSIGADD, csa_low_result, OP_EQUAL])),
+        # 11) OP_CHECKSIGADD with missing counter stack element
+        ("t11", CScript([pubs[1], OP_CHECKSIGADD, OP_1, OP_EQUAL])),
+        # 12) OP_CHECKSIG that needs invalid signature
+        ("t12", CScript([pubs[1], OP_CHECKSIGVERIFY, pubs[0], OP_CHECKSIG, OP_NOT])),
+        # 13) OP_CHECKSIG with empty key that needs invalid signature
+        ("t13", CScript([pubs[1], OP_CHECKSIGVERIFY, OP_0, OP_CHECKSIG, OP_NOT])),
+        # 14) OP_CHECKSIGADD that needs invalid signature
+        ("t14", CScript([pubs[1], OP_CHECKSIGVERIFY, OP_0, pubs[0], OP_CHECKSIGADD, OP_NOT])),
+        # 15) OP_CHECKSIGADD with empty key that needs invalid signature
+        ("t15", CScript([pubs[1], OP_CHECKSIGVERIFY, OP_0, OP_0, OP_CHECKSIGADD, OP_NOT])),
+        # 16) OP_CHECKSIG with unknown pubkey type
+        ("t16", CScript([OP_1, OP_CHECKSIG])),
+        # 17) OP_CHECKSIGADD with unknown pubkey type
+        ("t17", CScript([OP_0, OP_1, OP_CHECKSIGADD])),
+        # 18) OP_CHECKSIGVERIFY with unknown pubkey type
+        ("t18", CScript([OP_1, OP_CHECKSIGVERIFY, OP_1])),
+        # 19) script longer than 10000 bytes and over 201 non-push opcodes
+        ("t19", CScript([OP_0, OP_0, OP_2DROP] * 10001 + [pubs[1], OP_CHECKSIG])),
+        # 20) OP_CHECKSIGVERIFY with empty key
+        ("t20", CScript([pubs[1], OP_CHECKSIGVERIFY, OP_0, OP_0, OP_CHECKSIGVERIFY, OP_1])),
+        # 21) Script that grows the stack to 1000 elements
+        ("t21", CScript([pubs[1], OP_CHECKSIGVERIFY, OP_1] + [OP_DUP] * 999 + [OP_DROP] * 999)),
+        # 22) Script that grows the stack to 1001 elements
+        ("t22", CScript([pubs[1], OP_CHECKSIGVERIFY, OP_1] + [OP_DUP] * 1000 + [OP_DROP] * 1000)),
+        # 23) Script that expects an input stack of 1000 elements
+        ("t23", CScript([OP_DROP] * 999 + [pubs[1], OP_CHECKSIG])),
+        # 24) Script that expects an input stack of 1001 elements
+        ("t24", CScript([OP_DROP] * 1000 + [pubs[1], OP_CHECKSIG])),
+        # 25) Script that pushes a MAX_SCRIPT_ELEMENT_SIZE-bytes element
+        ("t25", CScript([random_bytes(MAX_SCRIPT_ELEMENT_SIZE), OP_DROP, pubs[1], OP_CHECKSIG])),
+        # 26) Script that pushes a (MAX_SCRIPT_ELEMENT_SIZE+1)-bytes element
+        ("t26", CScript([random_bytes(MAX_SCRIPT_ELEMENT_SIZE+1), OP_DROP, pubs[1], OP_CHECKSIG])),
+        # 27) CHECKSIGADD that must fail because numeric argument number is >4 bytes
+        ("t27", CScript([CScriptNum(OVERSIZE_NUMBER), pubs[1], OP_CHECKSIGADD])),
+        # 28) Pushes random CScriptNum value, checks OP_CHECKSIGADD result
+        ("t28", CScript([csa_high_val, pubs[1], OP_CHECKSIGADD, csa_high_result, OP_EQUAL])),
+        # 29) CHECKSIGADD that succeeds with proper sig because numeric argument number is <=4 bytes
+        ("t29", CScript([CScriptNum(OVERSIZE_NUMBER-1), pubs[1], OP_CHECKSIGADD])),
+        # 30) Variant of t1 with "normal" 33-byte pubkey
+        ("t30", CScript([b'\x03' + pubs[1], OP_CHECKSIG])),
+        # 31) Variant of t2 with "normal" 33-byte pubkey
+        ("t31", CScript([b'\x02' + pubs[1], OP_CHECKSIGVERIFY, OP_1])),
+        # 32) Variant of t28 with "normal" 33-byte pubkey
+        ("t32", CScript([csa_high_val, b'\x03' + pubs[1], OP_CHECKSIGADD, csa_high_result, OP_EQUAL])),
+        # 33) 999-of-999 multisig
+        ("t33", CScript(big_scriptops[:1998] + [OP_1])),
+        # 34) 1000-of-1000 multisig
+        ("t34", CScript(big_scriptops[:2000] + [OP_1])),
+        # 35) Variant of t9 that uses a non-minimally encoded input arg
+        ("t35", CScript([bytes([csa_low_val]), pubs[1], OP_CHECKSIGADD, csa_low_result, OP_EQUAL])),
+        # 36) Empty script
+        ("t36", CScript([])),
+    ]
+    # Add many dummies to test huge trees
+    for j in range(100000):
+        scripts.append((None, CScript([OP_RETURN, random.randrange(100000)])))
+    random.shuffle(scripts)
+    tap = taproot_construct(pubs[0], scripts)
+    common = {
+        "hashtype": hashtype,
+        "key": secs[1],
+        "tap": tap,
+    }
+    # Test that MAX_SCRIPT_ELEMENT_SIZE byte stack element inputs are valid, but not one more (and 80 bytes is standard but 81 is not).
+    add_spender(spenders, "tapscript/inputmaxlimit", leaf="t0", **common, standard=False, inputs=[getter("sign"), random_bytes(MAX_SCRIPT_ELEMENT_SIZE)], failure={"inputs": [getter("sign"), random_bytes(MAX_SCRIPT_ELEMENT_SIZE+1)]}, **ERR_PUSH_LIMIT)
+    add_spender(spenders, "tapscript/input80limit", leaf="t0", **common, inputs=[getter("sign"), random_bytes(80)])
+    add_spender(spenders, "tapscript/input81limit", leaf="t0", **common, standard=False, inputs=[getter("sign"), random_bytes(81)])
+    # Test that OP_CHECKMULTISIG and OP_CHECKMULTISIGVERIFY cause failure, but OP_CHECKSIG and OP_CHECKSIGVERIFY work.
+    add_spender(spenders, "tapscript/disabled_checkmultisig", leaf="t1", **common, **SINGLE_SIG, failure={"leaf": "t3"}, **ERR_TAPSCRIPT_CHECKMULTISIG)
+    add_spender(spenders, "tapscript/disabled_checkmultisigverify", leaf="t2", **common, **SINGLE_SIG, failure={"leaf": "t4"}, **ERR_TAPSCRIPT_CHECKMULTISIG)
+    # Test that OP_IF and OP_NOTIF do not accept non-0x01 as truth value (the MINIMALIF rule is consensus in Tapscript)
+    add_spender(spenders, "tapscript/minimalif", leaf="t5", **common, inputs=[getter("sign"), b'\x01'], failure={"inputs": [getter("sign"), b'\x02']}, **ERR_MINIMALIF)
+    add_spender(spenders, "tapscript/minimalnotif", leaf="t6", **common, inputs=[getter("sign"), b'\x01'], failure={"inputs": [getter("sign"), b'\x03']}, **ERR_MINIMALIF)
+    add_spender(spenders, "tapscript/minimalif", leaf="t5", **common, inputs=[getter("sign"), b'\x01'], failure={"inputs": [getter("sign"), b'\x0001']}, **ERR_MINIMALIF)
+    add_spender(spenders, "tapscript/minimalnotif", leaf="t6", **common, inputs=[getter("sign"), b'\x01'], failure={"inputs": [getter("sign"), b'\x0100']}, **ERR_MINIMALIF)
+    # Test that 1-byte public keys (which are unknown) are acceptable but nonstandard with unrelated signatures, but 0-byte public keys are not valid.
+    add_spender(spenders, "tapscript/unkpk/checksig", leaf="t16", standard=False, **common, **SINGLE_SIG, failure={"leaf": "t7"}, **ERR_UNKNOWN_PUBKEY)
+    add_spender(spenders, "tapscript/unkpk/checksigadd", leaf="t17", standard=False, **common, **SINGLE_SIG, failure={"leaf": "t10"}, **ERR_UNKNOWN_PUBKEY)
+    add_spender(spenders, "tapscript/unkpk/checksigverify", leaf="t18", standard=False, **common, **SINGLE_SIG, failure={"leaf": "t8"}, **ERR_UNKNOWN_PUBKEY)
+    # Test that 33-byte public keys (which are unknown) are acceptable but nonstandard with valid signatures, but normal pubkeys are not valid in that case.
+    add_spender(spenders, "tapscript/oldpk/checksig", leaf="t30", standard=False, **common, **SINGLE_SIG, sighash=bitflipper(default_sighash), failure={"leaf": "t1"}, **ERR_SIG_SCHNORR)
+    add_spender(spenders, "tapscript/oldpk/checksigadd", leaf="t31", standard=False, **common, **SINGLE_SIG, sighash=bitflipper(default_sighash), failure={"leaf": "t2"}, **ERR_SIG_SCHNORR)
+    add_spender(spenders, "tapscript/oldpk/checksigverify", leaf="t32", standard=False, **common, **SINGLE_SIG, sighash=bitflipper(default_sighash), failure={"leaf": "t28"}, **ERR_SIG_SCHNORR)
+    # Test that 0-byte public keys are not acceptable.
+    add_spender(spenders, "tapscript/emptypk/checksig", leaf="t1", **SINGLE_SIG, **common, failure={"leaf": "t7"}, **ERR_UNKNOWN_PUBKEY)
+    add_spender(spenders, "tapscript/emptypk/checksigverify", leaf="t2", **SINGLE_SIG, **common, failure={"leaf": "t8"}, **ERR_UNKNOWN_PUBKEY)
+    add_spender(spenders, "tapscript/emptypk/checksigadd", leaf="t9", **SINGLE_SIG, **common, failure={"leaf": "t10"}, **ERR_UNKNOWN_PUBKEY)
+    add_spender(spenders, "tapscript/emptypk/checksigadd", leaf="t35", standard=False, **SINGLE_SIG, **common, failure={"leaf": "t10"}, **ERR_UNKNOWN_PUBKEY)
+    # Test that OP_CHECKSIGADD results are as expected
+    add_spender(spenders, "tapscript/checksigaddresults", leaf="t28", **SINGLE_SIG, **common, failure={"leaf": "t27"}, err_msg="unknown error")
+    add_spender(spenders, "tapscript/checksigaddoversize", leaf="t29", **SINGLE_SIG, **common, failure={"leaf": "t27"}, err_msg="unknown error")
+    # Test that OP_CHECKSIGADD requires 3 stack elements.
+    add_spender(spenders, "tapscript/checksigadd3args", leaf="t9", **SINGLE_SIG, **common, failure={"leaf": "t11"}, **ERR_STACK_EMPTY)
+    # Test that empty signatures do not cause script failure in OP_CHECKSIG and OP_CHECKSIGADD (but do fail with empty pubkey, and do fail OP_CHECKSIGVERIFY)
+    add_spender(spenders, "tapscript/emptysigs/checksig", leaf="t12", **common, inputs=[b'', getter("sign")], failure={"leaf": "t13"}, **ERR_UNKNOWN_PUBKEY)
+    add_spender(spenders, "tapscript/emptysigs/nochecksigverify", leaf="t12", **common, inputs=[b'', getter("sign")], failure={"leaf": "t20"}, **ERR_UNKNOWN_PUBKEY)
+    add_spender(spenders, "tapscript/emptysigs/checksigadd", leaf="t14", **common, inputs=[b'', getter("sign")], failure={"leaf": "t15"}, **ERR_UNKNOWN_PUBKEY)
+    # Test that scripts over 10000 bytes (and over 201 non-push ops) are acceptable.
+    add_spender(spenders, "tapscript/no10000limit", leaf="t19", **SINGLE_SIG, **common)
+    # Test that a stack size of 1000 elements is permitted, but 1001 isn't.
+    add_spender(spenders, "tapscript/1000stack", leaf="t21", **SINGLE_SIG, **common, failure={"leaf": "t22"}, **ERR_STACK_SIZE)
+    # Test that an input stack size of 1000 elements is permitted, but 1001 isn't.
+    add_spender(spenders, "tapscript/1000inputs", leaf="t23", **common, inputs=[getter("sign")] + [b'' for _ in range(999)], failure={"leaf": "t24", "inputs": [getter("sign")] + [b'' for _ in range(1000)]}, **ERR_STACK_SIZE)
+    # Test that pushing a MAX_SCRIPT_ELEMENT_SIZE byte stack element is valid, but one longer is not.
+    add_spender(spenders, "tapscript/pushmaxlimit", leaf="t25", **common, **SINGLE_SIG, failure={"leaf": "t26"}, **ERR_PUSH_LIMIT)
+    # Test that 999-of-999 multisig works (but 1000-of-1000 triggers stack size limits)
+    add_spender(spenders, "tapscript/bigmulti", leaf="t33", **common, inputs=big_spend_inputs, num=999, failure={"leaf": "t34", "num": 1000}, **ERR_STACK_SIZE)
+    # Test that the CLEANSTACK rule is consensus critical in tapscript
+    add_spender(spenders, "tapscript/cleanstack", leaf="t36", tap=tap, inputs=[b'\x01'], failure={"inputs": [b'\x01', b'\x01']}, **ERR_CLEANSTACK)
+
+    # == Test for sigops ratio limit ==
+
+    # Given a number n, and a public key pk, functions that produce a (CScript, sigops). Each script takes as
+    # input a valid signature with the passed pk followed by a dummy push of bytes that are to be dropped, and
+    # will execute sigops signature checks.
+    SIGOPS_RATIO_SCRIPTS = [
+        # n OP_CHECKSIGVERFIYs and 1 OP_CHECKSIG.
+        lambda n, pk: (CScript([OP_DROP, pk] + [OP_2DUP, OP_CHECKSIGVERIFY] * n + [OP_CHECKSIG]), n + 1),
+        # n OP_CHECKSIGVERIFYs and 1 OP_CHECKSIGADD, but also one unexecuted OP_CHECKSIGVERIFY.
+        lambda n, pk: (CScript([OP_DROP, pk, OP_0, OP_IF, OP_2DUP, OP_CHECKSIGVERIFY, OP_ENDIF] + [OP_2DUP, OP_CHECKSIGVERIFY] * n + [OP_2, OP_SWAP, OP_CHECKSIGADD, OP_3, OP_EQUAL]), n + 1),
+        # n OP_CHECKSIGVERIFYs and 1 OP_CHECKSIGADD, but also one unexecuted OP_CHECKSIG.
+        lambda n, pk: (CScript([random_bytes(220), OP_2DROP, pk, OP_1, OP_NOTIF, OP_2DUP, OP_CHECKSIG, OP_VERIFY, OP_ENDIF] + [OP_2DUP, OP_CHECKSIGVERIFY] * n + [OP_4, OP_SWAP, OP_CHECKSIGADD, OP_5, OP_EQUAL]), n + 1),
+        # n OP_CHECKSIGVERFIYs and 1 OP_CHECKSIGADD, but also one unexecuted OP_CHECKSIGADD.
+        lambda n, pk: (CScript([OP_DROP, pk, OP_1, OP_IF, OP_ELSE, OP_2DUP, OP_6, OP_SWAP, OP_CHECKSIGADD, OP_7, OP_EQUALVERIFY, OP_ENDIF] + [OP_2DUP, OP_CHECKSIGVERIFY] * n + [OP_8, OP_SWAP, OP_CHECKSIGADD, OP_9, OP_EQUAL]), n + 1),
+        # n+1 OP_CHECKSIGs, but also one OP_CHECKSIG with an empty signature.
+        lambda n, pk: (CScript([OP_DROP, OP_0, pk, OP_CHECKSIG, OP_NOT, OP_VERIFY, pk] + [OP_2DUP, OP_CHECKSIG, OP_VERIFY] * n + [OP_CHECKSIG]), n + 1),
+        # n OP_CHECKSIGADDs and 1 OP_CHECKSIG, but also an OP_CHECKSIGADD with an empty signature.
+        lambda n, pk: (CScript([OP_DROP, OP_0, OP_10, pk, OP_CHECKSIGADD, OP_10, OP_EQUALVERIFY, pk] + [OP_2DUP, OP_16, OP_SWAP, OP_CHECKSIGADD, b'\x11', OP_EQUALVERIFY] * n + [OP_CHECKSIG]), n + 1),
+    ]
+    for annex in [None, bytes([ANNEX_TAG]) + random_bytes(random.randrange(1000))]:
+        for hashtype in [SIGHASH_DEFAULT, SIGHASH_ALL]:
+            for pubkey in [pubs[1], random_bytes(random.choice([x for x in range(2, 81) if x != 32]))]:
+                for fn_num, fn in enumerate(SIGOPS_RATIO_SCRIPTS):
+                    merkledepth = random.randrange(129)
+
+
+                    def predict_sigops_ratio(n, dummy_size):
+                        """Predict whether spending fn(n, pubkey) with dummy_size will pass the ratio test."""
+                        script, sigops = fn(n, pubkey)
+                        # Predict the size of the witness for a given choice of n
+                        stacklen_size = 1
+                        sig_size = 64 + (hashtype != SIGHASH_DEFAULT)
+                        siglen_size = 1
+                        dummylen_size = 1 + 2 * (dummy_size >= 253)
+                        script_size = len(script)
+                        scriptlen_size = 1 + 2 * (script_size >= 253)
+                        control_size = 33 + 32 * merkledepth
+                        controllen_size = 1 + 2 * (control_size >= 253)
+                        annex_size = 0 if annex is None else len(annex)
+                        annexlen_size = 0 if annex is None else 1 + 2 * (annex_size >= 253)
+                        witsize = stacklen_size + sig_size + siglen_size + dummy_size + dummylen_size + script_size + scriptlen_size + control_size + controllen_size + annex_size + annexlen_size
+                        # sigops ratio test
+                        return witsize + 50 >= 50 * sigops
+                    # Make sure n is high enough that with empty dummy, the script is not valid
+                    n = 0
+                    while predict_sigops_ratio(n, 0):
+                        n += 1
+                    # But allow picking a bit higher still
+                    n += random.randrange(5)
+                    # Now pick dummy size *just* large enough that the overall construction passes
+                    dummylen = 0
+                    while not predict_sigops_ratio(n, dummylen):
+                        dummylen += 1
+                    scripts = [("s", fn(n, pubkey)[0])]
+                    for _ in range(merkledepth):
+                        scripts = [scripts, random.choice(PARTNER_MERKLE_FN)]
+                    tap = taproot_construct(pubs[0], scripts)
+                    standard = annex is None and dummylen <= 80 and len(pubkey) == 32
+                    add_spender(spenders, "tapscript/sigopsratio_%i" % fn_num, tap=tap, leaf="s", annex=annex, hashtype=hashtype, key=secs[1], inputs=[getter("sign"), random_bytes(dummylen)], standard=standard, failure={"inputs": [getter("sign"), random_bytes(dummylen - 1)]}, **ERR_SIGOPS_RATIO)
+
+    # Future leaf versions
+    for leafver in range(0, 0x100, 2):
+        if leafver == LEAF_VERSION_TAPSCRIPT or leafver == ANNEX_TAG:
+            # Skip the defined LEAF_VERSION_TAPSCRIPT, and the ANNEX_TAG which is not usable as leaf version
+            continue
+        scripts = [
+            ("bare_c0", CScript([OP_NOP])),
+            ("bare_unkver", CScript([OP_NOP]), leafver),
+            ("return_c0", CScript([OP_RETURN])),
+            ("return_unkver", CScript([OP_RETURN]), leafver),
+            ("undecodable_c0", CScript([OP_PUSHDATA1])),
+            ("undecodable_unkver", CScript([OP_PUSHDATA1]), leafver),
+            ("bigpush_c0", CScript([random_bytes(MAX_SCRIPT_ELEMENT_SIZE+1), OP_DROP])),
+            ("bigpush_unkver", CScript([random_bytes(MAX_SCRIPT_ELEMENT_SIZE+1), OP_DROP]), leafver),
+            ("1001push_c0", CScript([OP_0] * 1001)),
+            ("1001push_unkver", CScript([OP_0] * 1001), leafver),
+        ]
+        random.shuffle(scripts)
+        tap = taproot_construct(pubs[0], scripts)
+        add_spender(spenders, "unkver/bare", standard=False, tap=tap, leaf="bare_unkver", failure={"leaf": "bare_c0"}, **ERR_CLEANSTACK)
+        add_spender(spenders, "unkver/return", standard=False, tap=tap, leaf="return_unkver", failure={"leaf": "return_c0"}, **ERR_OP_RETURN)
+        add_spender(spenders, "unkver/undecodable", standard=False, tap=tap, leaf="undecodable_unkver", failure={"leaf": "undecodable_c0"}, **ERR_UNDECODABLE)
+        add_spender(spenders, "unkver/bigpush", standard=False, tap=tap, leaf="bigpush_unkver", failure={"leaf": "bigpush_c0"}, **ERR_PUSH_LIMIT)
+        add_spender(spenders, "unkver/1001push", standard=False, tap=tap, leaf="1001push_unkver", failure={"leaf": "1001push_c0"}, **ERR_STACK_SIZE)
+        add_spender(spenders, "unkver/1001inputs", standard=False, tap=tap, leaf="bare_unkver", inputs=[b'']*1001, failure={"leaf": "bare_c0"}, **ERR_STACK_SIZE)
+
+    # OP_SUCCESSx tests.
+    hashtype = lambda _: random.choice(VALID_SIGHASHES_TAPROOT)
+    for opval in range(76, 0x100):
+        opcode = CScriptOp(opval)
+        if not is_op_success(opcode):
+            continue
+        scripts = [
+            ("bare_success", CScript([opcode])),
+            ("bare_nop", CScript([OP_NOP])),
+            ("unexecif_success", CScript([OP_0, OP_IF, opcode, OP_ENDIF])),
+            ("unexecif_nop", CScript([OP_0, OP_IF, OP_NOP, OP_ENDIF])),
+            ("return_success", CScript([OP_RETURN, opcode])),
+            ("return_nop", CScript([OP_RETURN, OP_NOP])),
+            ("undecodable_success", CScript([opcode, OP_PUSHDATA1])),
+            ("undecodable_nop", CScript([OP_NOP, OP_PUSHDATA1])),
+            ("undecodable_bypassed_success", CScript([OP_PUSHDATA1, OP_2, opcode])),
+            ("bigpush_success", CScript([random_bytes(MAX_SCRIPT_ELEMENT_SIZE+1), OP_DROP, opcode])),
+            ("bigpush_nop", CScript([random_bytes(MAX_SCRIPT_ELEMENT_SIZE+1), OP_DROP, OP_NOP])),
+            ("1001push_success", CScript([OP_0] * 1001 + [opcode])),
+            ("1001push_nop", CScript([OP_0] * 1001 + [OP_NOP])),
+        ]
+        random.shuffle(scripts)
+        tap = taproot_construct(pubs[0], scripts)
+        add_spender(spenders, "opsuccess/bare", standard=False, tap=tap, leaf="bare_success", failure={"leaf": "bare_nop"}, **ERR_CLEANSTACK)
+        add_spender(spenders, "opsuccess/unexecif", standard=False, tap=tap, leaf="unexecif_success", failure={"leaf": "unexecif_nop"}, **ERR_CLEANSTACK)
+        add_spender(spenders, "opsuccess/return", standard=False, tap=tap, leaf="return_success", failure={"leaf": "return_nop"}, **ERR_OP_RETURN)
+        add_spender(spenders, "opsuccess/undecodable", standard=False, tap=tap, leaf="undecodable_success", failure={"leaf": "undecodable_nop"}, **ERR_UNDECODABLE)
+        add_spender(spenders, "opsuccess/undecodable_bypass", standard=False, tap=tap, leaf="undecodable_success", failure={"leaf": "undecodable_bypassed_success"}, **ERR_UNDECODABLE)
+        add_spender(spenders, "opsuccess/bigpush", standard=False, tap=tap, leaf="bigpush_success", failure={"leaf": "bigpush_nop"}, **ERR_PUSH_LIMIT)
+        add_spender(spenders, "opsuccess/1001push", standard=False, tap=tap, leaf="1001push_success", failure={"leaf": "1001push_nop"}, **ERR_STACK_SIZE)
+        add_spender(spenders, "opsuccess/1001inputs", standard=False, tap=tap, leaf="bare_success", inputs=[b'']*1001, failure={"leaf": "bare_nop"}, **ERR_STACK_SIZE)
+
+    # Non-OP_SUCCESSx (verify that those aren't accidentally treated as OP_SUCCESSx)
+    for opval in range(0, 0x100):
+        opcode = CScriptOp(opval)
+        if is_op_success(opcode):
+            continue
+        scripts = [
+            ("normal", CScript([OP_RETURN, opcode] + [OP_NOP] * 75)),
+            ("op_success", CScript([OP_RETURN, CScriptOp(0x50)]))
+        ]
+        tap = taproot_construct(pubs[0], scripts)
+        add_spender(spenders, "alwaysvalid/notsuccessx", tap=tap, leaf="op_success", inputs=[], standard=False, failure={"leaf": "normal"}) # err_msg differs based on opcode
+
+    # == Legacy tests ==
+
+    # Also add a few legacy spends into the mix, so that transactions which combine taproot and pre-taproot spends get tested too.
+    for compressed in [False, True]:
+        eckey1 = ECKey()
+        eckey1.set(generate_privkey(), compressed)
+        pubkey1 = eckey1.get_pubkey().get_bytes()
+        eckey2 = ECKey()
+        eckey2.set(generate_privkey(), compressed)
+        for p2sh in [False, True]:
+            for witv0 in [False, True]:
+                for hashtype in VALID_SIGHASHES_ECDSA + [random.randrange(0x04, 0x80), random.randrange(0x84, 0x100)]:
+                    standard = (hashtype in VALID_SIGHASHES_ECDSA) and (compressed or not witv0)
+                    add_spender(spenders, "legacy/pk-wrongkey", hashtype=hashtype, p2sh=p2sh, witv0=witv0, standard=standard, script=CScript([pubkey1, OP_CHECKSIG]), **SINGLE_SIG, key=eckey1, failure={"key": eckey2}, sigops_weight=4-3*witv0, **ERR_NO_SUCCESS)
+                    add_spender(spenders, "legacy/pkh-sighashflip", hashtype=hashtype, p2sh=p2sh, witv0=witv0, standard=standard, pkh=pubkey1, key=eckey1, **SIGHASH_BITFLIP, sigops_weight=4-3*witv0, **ERR_NO_SUCCESS)
+
+    # Verify that OP_CHECKSIGADD wasn't accidentally added to pre-taproot validation logic.
+    for p2sh in [False, True]:
+        for witv0 in [False, True]:
+            for hashtype in VALID_SIGHASHES_ECDSA + [random.randrange(0x04, 0x80), random.randrange(0x84, 0x100)]:
+                standard = hashtype in VALID_SIGHASHES_ECDSA and (p2sh or witv0)
+                add_spender(spenders, "compat/nocsa", hashtype=hashtype, p2sh=p2sh, witv0=witv0, standard=standard, script=CScript([OP_IF, OP_11, pubkey1, OP_CHECKSIGADD, OP_12, OP_EQUAL, OP_ELSE, pubkey1, OP_CHECKSIG, OP_ENDIF]), key=eckey1, sigops_weight=4-3*witv0, inputs=[getter("sign"), b''], failure={"inputs": [getter("sign"), b'\x01']}, **ERR_UNDECODABLE)
+
+    return spenders
+
+def spenders_taproot_inactive():
+    """Spenders for testing that pre-activation Taproot rules don't apply."""
+
+    spenders = []
+
+    sec = generate_privkey()
+    pub, _ = compute_xonly_pubkey(sec)
+    scripts = [
+        ("pk", CScript([pub, OP_CHECKSIG])),
+        ("future_leaf", CScript([pub, OP_CHECKSIG]), 0xc2),
+        ("op_success", CScript([pub, OP_CHECKSIG, OP_0, OP_IF, CScriptOp(0x50), OP_ENDIF])),
+    ]
+    tap = taproot_construct(pub, scripts)
+
+    # Test that keypath spending is valid & standard if compliant, but valid and nonstandard otherwise.
+    add_spender(spenders, "inactive/keypath_valid", key=sec, tap=tap)
+    add_spender(spenders, "inactive/keypath_invalidsig", key=sec, tap=tap, standard=False, sighash=bitflipper(default_sighash))
+    add_spender(spenders, "inactive/keypath_empty", key=sec, tap=tap, standard=False, witness=[])
+
+    # Same for scriptpath spending (but using future features like annex, leaf versions, or OP_SUCCESS is nonstandard).
+    add_spender(spenders, "inactive/scriptpath_valid", key=sec, tap=tap, leaf="pk", inputs=[getter("sign")])
+    add_spender(spenders, "inactive/scriptpath_invalidsig", key=sec, tap=tap, leaf="pk", standard=False, inputs=[getter("sign")], sighash=bitflipper(default_sighash))
+    add_spender(spenders, "inactive/scriptpath_invalidcb", key=sec, tap=tap, leaf="pk", standard=False, inputs=[getter("sign")], controlblock=bitflipper(default_controlblock))
+    add_spender(spenders, "inactive/scriptpath_valid_unkleaf", key=sec, tap=tap, leaf="future_leaf", standard=False, inputs=[getter("sign")])
+    add_spender(spenders, "inactive/scriptpath_invalid_unkleaf", key=sec, tap=tap, leaf="future_leaf", standard=False, inputs=[getter("sign")], sighash=bitflipper(default_sighash))
+    add_spender(spenders, "inactive/scriptpath_valid_opsuccess", key=sec, tap=tap, leaf="op_success", standard=False, inputs=[getter("sign")])
+    add_spender(spenders, "inactive/scriptpath_valid_opsuccess", key=sec, tap=tap, leaf="op_success", standard=False, inputs=[getter("sign")], sighash=bitflipper(default_sighash))
+
+    return spenders
+
+# Data type to keep track of UTXOs, where they were created, and how to spend them.
+UTXOData = namedtuple('UTXOData', 'outpoint,output,spender')
+
+class TaprootTest(BitcoinTestFramework):
+
+    def skip_test_if_missing_module(self):
+        self.skip_if_no_wallet()
+
+    def set_test_params(self):
+        self.num_nodes = 2
+        self.setup_clean_chain = True
+        # Node 0 has Taproot inactive, Node 1 active.
+        self.extra_args = [["-whitelist=127.0.0.1", "-par=1", "-vbparams=taproot:1:1"], ["-whitelist=127.0.0.1", "-par=1"]]
+
+    def block_submit(self, node, txs, msg, err_msg, cb_pubkey=None, fees=0, sigops_weight=0, witness=False, accept=False):
+
+        # Deplete block of any non-tapscript sigops using a single additional 0-value coinbase output.
+        # It is not impossible to fit enough tapscript sigops to hit the old 80k limit without
+        # busting txin-level limits. We simply have to account for the p2pk outputs in all
+        # transactions.
+        extra_output_script = CScript([OP_CHECKSIG]*((MAX_BLOCK_SIGOPS_WEIGHT - sigops_weight) // WITNESS_SCALE_FACTOR))
+
+        block = create_block(self.tip, create_coinbase(self.lastblockheight + 1, pubkey=cb_pubkey, extra_output_script=extra_output_script, fees=fees), self.lastblocktime + 1)
+        block.nVersion = 4
+        for tx in txs:
+            tx.rehash()
+            block.vtx.append(tx)
+        block.hashMerkleRoot = block.calc_merkle_root()
+        witness and add_witness_commitment(block)
+        block.rehash()
+        block.solve()
+        block_response = node.submitblock(block.serialize(True).hex())
+        if err_msg is not None:
+            assert block_response is not None and err_msg in block_response, "Missing error message '%s' from block response '%s': %s" % (err_msg, "(None)" if block_response is None else block_response, msg)
+        if (accept):
+            assert node.getbestblockhash() == block.hash, "Failed to accept: %s (response: %s)" % (msg, block_response)
+            self.tip = block.sha256
+            self.lastblockhash = block.hash
+            self.lastblocktime += 1
+            self.lastblockheight += 1
+        else:
+            assert node.getbestblockhash() == self.lastblockhash, "Failed to reject: " + msg
+
+    def test_spenders(self, node, spenders, input_counts):
+        """Run randomized tests with a number of "spenders".
+
+        Steps:
+            1) Generate an appropriate UTXO for each spender to test spend conditions
+            2) Generate 100 random addresses of all wallet types: pkh/sh_wpkh/wpkh
+            3) Select random number of inputs from (1)
+            4) Select random number of addresses from (2) as outputs
+
+        Each spender embodies a test; in a large randomized test, it is verified
+        that toggling the valid argument to each lambda toggles the validity of
+        the transaction. This is accomplished by constructing transactions consisting
+        of all valid inputs, except one invalid one.
+        """
+
+        # Construct a bunch of sPKs that send coins back to the host wallet
+        self.log.info("- Constructing addresses for returning coins")
+        host_spks = []
+        host_pubkeys = []
+        for i in range(16):
+            addr = node.getnewaddress(address_type=random.choice(["legacy", "p2sh-segwit", "bech32"]))
+            info = node.getaddressinfo(addr)
+            spk = bytes.fromhex(info['scriptPubKey'])
+            host_spks.append(spk)
+            host_pubkeys.append(bytes.fromhex(info['pubkey']))
+
+        # Initialize variables used by block_submit().
+        self.lastblockhash = node.getbestblockhash()
+        self.tip = int(self.lastblockhash, 16)
+        block = node.getblock(self.lastblockhash)
+        self.lastblockheight = block['height']
+        self.lastblocktime = block['time']
+
+        # Create transactions spending up to 50 of the wallet's inputs, with one output for each spender, and
+        # one change output at the end. The transaction is constructed on the Python side to enable
+        # having multiple outputs to the same address and outputs with no assigned address. The wallet
+        # is then asked to sign it through signrawtransactionwithwallet, and then added to a block on the
+        # Python side (to bypass standardness rules).
+        self.log.info("- Creating test UTXOs...")
+        random.shuffle(spenders)
+        normal_utxos = []
+        mismatching_utxos = [] # UTXOs with input that requires mismatching output position
+        done = 0
+        while done < len(spenders):
+            # Compute how many UTXOs to create with this transaction
+            count_this_tx = min(len(spenders) - done, (len(spenders) + 4) // 5, 10000)
+
+            fund_tx = CTransaction()
+            # Add the 50 highest-value inputs
+            unspents = node.listunspent()
+            random.shuffle(unspents)
+            unspents.sort(key=lambda x: int(x["amount"] * 100000000), reverse=True)
+            if len(unspents) > 50:
+                unspents = unspents[:50]
+            random.shuffle(unspents)
+            balance = 0
+            for unspent in unspents:
+                balance += int(unspent["amount"] * 100000000)
+                txid = int(unspent["txid"], 16)
+                fund_tx.vin.append(CTxIn(COutPoint(txid, int(unspent["vout"])), CScript()))
+            # Add outputs
+            cur_progress = done / len(spenders)
+            next_progress = (done + count_this_tx) / len(spenders)
+            change_goal = (1.0 - 0.6 * next_progress) / (1.0 - 0.6 * cur_progress) * balance
+            self.log.debug("Create %i UTXOs in a transaction spending %i inputs worth %.8f (sending ~%.8f to change)" % (count_this_tx, len(unspents), balance * 0.00000001, change_goal * 0.00000001))
+            for i in range(count_this_tx):
+                avg = (balance - change_goal) / (count_this_tx - i)
+                amount = int(random.randrange(int(avg*0.85 + 0.5), int(avg*1.15 + 0.5)) + 0.5)
+                balance -= amount
+                fund_tx.vout.append(CTxOut(amount, spenders[done + i].script))
+            # Add change
+            fund_tx.vout.append(CTxOut(balance - 10000, random.choice(host_spks)))
+            # Ask the wallet to sign
+            ss = BytesIO(bytes.fromhex(node.signrawtransactionwithwallet(ToHex(fund_tx))["hex"]))
+            fund_tx.deserialize(ss)
+            # Construct UTXOData entries
+            fund_tx.rehash()
+            for i in range(count_this_tx):
+                utxodata = UTXOData(outpoint=COutPoint(fund_tx.sha256, i), output=fund_tx.vout[i], spender=spenders[done])
+                if utxodata.spender.need_vin_vout_mismatch:
+                    mismatching_utxos.append(utxodata)
+                else:
+                    normal_utxos.append(utxodata)
+                done += 1
+            # Mine into a block
+            self.block_submit(node, [fund_tx], "Funding tx", None, random.choice(host_pubkeys), 10000, MAX_BLOCK_SIGOPS_WEIGHT, True, True)
+
+        # Consume groups of choice(input_coins) from utxos in a tx, testing the spenders.
+        self.log.info("- Running %i spending tests" % done)
+        random.shuffle(normal_utxos)
+        random.shuffle(mismatching_utxos)
+        assert done == len(normal_utxos) + len(mismatching_utxos)
+
+        left = done
+        while left:
+            # Construct CTransaction with random nVersion, nLocktime
+            tx = CTransaction()
+            tx.nVersion = random.choice([1, 2, random.randint(-0x80000000, 0x7fffffff)])
+            min_sequence = (tx.nVersion != 1 and tx.nVersion != 0) * 0x80000000  # The minimum sequence number to disable relative locktime
+            if random.choice([True, False]):
+                tx.nLockTime = random.randrange(LOCKTIME_THRESHOLD, self.lastblocktime - 7200)  # all absolute locktimes in the past
+            else:
+                tx.nLockTime = random.randrange(self.lastblockheight + 1)  # all block heights in the past
+
+            # Decide how many UTXOs to test with.
+            acceptable = [n for n in input_counts if n <= left and (left - n > max(input_counts) or (left - n) in [0] + input_counts)]
+            num_inputs = random.choice(acceptable)
+
+            # If we have UTXOs that require mismatching inputs/outputs left, include exactly one of those
+            # unless there is only one normal UTXO left (as tests with mismatching UTXOs require at least one
+            # normal UTXO to go in the first position), and we don't want to run out of normal UTXOs.
+            input_utxos = []
+            while len(mismatching_utxos) and (len(input_utxos) == 0 or len(normal_utxos) == 1):
+                input_utxos.append(mismatching_utxos.pop())
+                left -= 1
+
+            # Top up until we hit num_inputs (but include at least one normal UTXO always).
+            for _ in range(max(1, num_inputs - len(input_utxos))):
+                input_utxos.append(normal_utxos.pop())
+                left -= 1
+
+            # The first input cannot require a mismatching output (as there is at least one output).
+            while True:
+                random.shuffle(input_utxos)
+                if not input_utxos[0].spender.need_vin_vout_mismatch:
+                    break
+            first_mismatch_input = None
+            for i in range(len(input_utxos)):
+                if input_utxos[i].spender.need_vin_vout_mismatch:
+                    first_mismatch_input = i
+            assert first_mismatch_input is None or first_mismatch_input > 0
+
+            # Decide fee, and add CTxIns to tx.
+            amount = sum(utxo.output.nValue for utxo in input_utxos)
+            fee = min(random.randrange(MIN_FEE * 2, MIN_FEE * 4), amount - DUST_LIMIT)  # 10000-20000 sat fee
+            in_value = amount - fee
+            tx.vin = [CTxIn(outpoint=utxo.outpoint, nSequence=random.randint(min_sequence, 0xffffffff)) for utxo in input_utxos]
+            tx.wit.vtxinwit = [CTxInWitness() for _ in range(len(input_utxos))]
+            sigops_weight = sum(utxo.spender.sigops_weight for utxo in input_utxos)
+            self.log.debug("Test: %s" % (", ".join(utxo.spender.comment for utxo in input_utxos)))
+
+            # Add 1 to 4 random outputs (but constrained by inputs that require mismatching outputs)
+            num_outputs = random.choice(range(1, 1 + min(4, 4 if first_mismatch_input is None else first_mismatch_input)))
+            assert in_value >= 0 and fee - num_outputs * DUST_LIMIT >= MIN_FEE
+            for i in range(num_outputs):
+                tx.vout.append(CTxOut())
+                if in_value <= DUST_LIMIT:
+                    tx.vout[-1].nValue = DUST_LIMIT
+                elif i < num_outputs - 1:
+                    tx.vout[-1].nValue = in_value
+                else:
+                    tx.vout[-1].nValue = random.randint(DUST_LIMIT, in_value)
+                in_value -= tx.vout[-1].nValue
+                tx.vout[-1].scriptPubKey = random.choice(host_spks)
+                sigops_weight += CScript(tx.vout[-1].scriptPubKey).GetSigOpCount(False) * WITNESS_SCALE_FACTOR
+            fee += in_value
+            assert fee >= 0
+
+            # Select coinbase pubkey
+            cb_pubkey = random.choice(host_pubkeys)
+            sigops_weight += 1 * WITNESS_SCALE_FACTOR
+
+            # Precompute one satisfying and one failing scriptSig/witness for each input.
+            input_data = []
+            for i in range(len(input_utxos)):
+                fn = input_utxos[i].spender.sat_function
+                fail = None
+                success = fn(tx, i, [utxo.output for utxo in input_utxos], True)
+                if not input_utxos[i].spender.no_fail:
+                    fail = fn(tx, i, [utxo.output for utxo in input_utxos], False)
+                input_data.append((fail, success))
+
+            # Sign each input incorrectly once on each complete signing pass, except the very last.
+            for fail_input in list(range(len(input_utxos))) + [None]:
+                # Skip trying to fail at spending something that can't be made to fail.
+                if fail_input is not None and input_utxos[fail_input].spender.no_fail:
+                    continue
+                # Expected message with each input failure, may be None(which is ignored)
+                expected_fail_msg = None if fail_input is None else input_utxos[fail_input].spender.err_msg
+                # Fill inputs/witnesses
+                for i in range(len(input_utxos)):
+                    tx.vin[i].scriptSig = input_data[i][i != fail_input][0]
+                    tx.wit.vtxinwit[i].scriptWitness.stack = input_data[i][i != fail_input][1]
+                # Submit to mempool to check standardness
+                is_standard_tx = fail_input is None and all(utxo.spender.is_standard for utxo in input_utxos) and tx.nVersion >= 1 and tx.nVersion <= 2
+                tx.rehash()
+                msg = ','.join(utxo.spender.comment + ("*" if n == fail_input else "") for n, utxo in enumerate(input_utxos))
+                if is_standard_tx:
+                    node.sendrawtransaction(tx.serialize().hex(), 0)
+                    assert node.getmempoolentry(tx.hash) is not None, "Failed to accept into mempool: " + msg
+                else:
+                    assert_raises_rpc_error(-26, None, node.sendrawtransaction, tx.serialize().hex(), 0)
+                # Submit in a block
+                self.block_submit(node, [tx], msg, witness=True, accept=fail_input is None, cb_pubkey=cb_pubkey, fees=fee, sigops_weight=sigops_weight, err_msg=expected_fail_msg)
+
+            if (len(spenders) - left) // 200 > (len(spenders) - left - len(input_utxos)) // 200:
+                self.log.info("  - %i tests done" % (len(spenders) - left))
+
+        assert left == 0
+        assert len(normal_utxos) == 0
+        assert len(mismatching_utxos) == 0
+        self.log.info("  - Done")
+
+    def run_test(self):
+        self.connect_nodes(0, 1)
+
+        # Post-taproot activation tests go first (pre-taproot tests' blocks are invalid post-taproot).
+        self.log.info("Post-activation tests...")
+        self.nodes[1].generate(101)
+        self.test_spenders(self.nodes[1], spenders_taproot_active(), input_counts=[1, 2, 2, 2, 2, 3])
+
+        # Transfer % of funds to pre-taproot node.
+        addr = self.nodes[0].getnewaddress()
+        self.nodes[1].sendtoaddress(address=addr, amount=int(self.nodes[1].getbalance() * 70000000) / 100000000)
+        self.nodes[1].generate(1)
+        self.sync_blocks()
+
+        # Pre-taproot activation tests.
+        self.log.info("Pre-activation tests...")
+        self.test_spenders(self.nodes[0], spenders_taproot_inactive(), input_counts=[1, 2, 2, 2, 2, 3])
+
+
+if __name__ == '__main__':
+    TaprootTest().main()
diff --git a/test/functional/test_framework/blocktools.py b/test/functional/test_framework/blocktools.py
index afc1995009..4be8b7d80b 100644
--- a/test/functional/test_framework/blocktools.py
+++ b/test/functional/test_framework/blocktools.py
@@ -43,7 +43,9 @@ from .script import (
 from .util import assert_equal
 from io import BytesIO
 
+WITNESS_SCALE_FACTOR = 4
 MAX_BLOCK_SIGOPS = 20000
+MAX_BLOCK_SIGOPS_WEIGHT = MAX_BLOCK_SIGOPS * WITNESS_SCALE_FACTOR
 
 # Genesis block time (regtest)
 TIME_GENESIS_BLOCK = 1296688602
@@ -101,22 +103,31 @@ def script_BIP34_coinbase_height(height):
     return CScript([CScriptNum(height)])
 
 
-def create_coinbase(height, pubkey=None):
-    """Create a coinbase transaction, assuming no miner fees.
+def create_coinbase(height, pubkey=None, extra_output_script=None, fees=0):
+    """Create a coinbase transaction.
 
     If pubkey is passed in, the coinbase output will be a P2PK output;
-    otherwise an anyone-can-spend output."""
+    otherwise an anyone-can-spend output.
+
+    If extra_output_script is given, make a 0-value output to that
+    script. This is useful to pad block weight/sigops as needed. """
     coinbase = CTransaction()
     coinbase.vin.append(CTxIn(COutPoint(0, 0xffffffff), script_BIP34_coinbase_height(height), 0xffffffff))
     coinbaseoutput = CTxOut()
     coinbaseoutput.nValue = 50 * COIN
     halvings = int(height / 150)  # regtest
     coinbaseoutput.nValue >>= halvings
-    if (pubkey is not None):
+    coinbaseoutput.nValue += fees
+    if pubkey is not None:
         coinbaseoutput.scriptPubKey = CScript([pubkey, OP_CHECKSIG])
     else:
         coinbaseoutput.scriptPubKey = CScript([OP_TRUE])
     coinbase.vout = [coinbaseoutput]
+    if extra_output_script is not None:
+        coinbaseoutput2 = CTxOut()
+        coinbaseoutput2.nValue = 0
+        coinbaseoutput2.scriptPubKey = extra_output_script
+        coinbase.vout.append(coinbaseoutput2)
     coinbase.calc_sha256()
     return coinbase
 
diff --git a/test/functional/test_framework/key.py b/test/functional/test_framework/key.py
index c9f09a31aa..17b869e542 100644
--- a/test/functional/test_framework/key.py
+++ b/test/functional/test_framework/key.py
@@ -476,7 +476,7 @@ def verify_schnorr(key, sig, msg):
         return False
     return True
 
-def sign_schnorr(key, msg, aux=None):
+def sign_schnorr(key, msg, aux=None, flip_p=False, flip_r=False):
     """Create a Schnorr signature (see BIP 340)."""
 
     if aux is None:
@@ -490,13 +490,13 @@ def sign_schnorr(key, msg, aux=None):
     if sec == 0 or sec >= SECP256K1_ORDER:
         return None
     P = SECP256K1.affine(SECP256K1.mul([(SECP256K1_G, sec)]))
-    if not SECP256K1.has_even_y(P):
+    if SECP256K1.has_even_y(P) == flip_p:
         sec = SECP256K1_ORDER - sec
     t = (sec ^ int.from_bytes(TaggedHash("BIP0340/aux", aux), 'big')).to_bytes(32, 'big')
     kp = int.from_bytes(TaggedHash("BIP0340/nonce", t + P[0].to_bytes(32, 'big') + msg), 'big') % SECP256K1_ORDER
     assert kp != 0
     R = SECP256K1.affine(SECP256K1.mul([(SECP256K1_G, kp)]))
-    k = kp if SECP256K1.has_even_y(R) else SECP256K1_ORDER - kp
+    k = kp if SECP256K1.has_even_y(R) != flip_r else SECP256K1_ORDER - kp
     e = int.from_bytes(TaggedHash("BIP0340/challenge", R[0].to_bytes(32, 'big') + P[0].to_bytes(32, 'big') + msg), 'big') % SECP256K1_ORDER
     return R[0].to_bytes(32, 'big') + ((k + e * sec) % SECP256K1_ORDER).to_bytes(32, 'big')
 
diff --git a/test/functional/test_framework/script.py b/test/functional/test_framework/script.py
index 5e35ba0fce..8e5848d493 100644
--- a/test/functional/test_framework/script.py
+++ b/test/functional/test_framework/script.py
@@ -6,11 +6,15 @@
 
 This file is modified from python-bitcoinlib.
 """
+
+from collections import namedtuple
 import hashlib
 import struct
 import unittest
 from typing import List, Dict
 
+from .key import TaggedHash, tweak_add_pubkey
+
 from .messages import (
     CTransaction,
     CTxOut,
@@ -22,8 +26,13 @@ from .messages import (
 )
 
 MAX_SCRIPT_ELEMENT_SIZE = 520
+LOCKTIME_THRESHOLD = 500000000
+ANNEX_TAG = 0x50
+
 OPCODE_NAMES = {}  # type: Dict[CScriptOp, str]
 
+LEAF_VERSION_TAPSCRIPT = 0xc0
+
 def hash160(s):
     return hashlib.new('ripemd160', sha256(s)).digest()
 
@@ -239,11 +248,8 @@ OP_NOP8 = CScriptOp(0xb7)
 OP_NOP9 = CScriptOp(0xb8)
 OP_NOP10 = CScriptOp(0xb9)
 
-# template matching params
-OP_SMALLINTEGER = CScriptOp(0xfa)
-OP_PUBKEYS = CScriptOp(0xfb)
-OP_PUBKEYHASH = CScriptOp(0xfd)
-OP_PUBKEY = CScriptOp(0xfe)
+# BIP 342 opcodes (Tapscript)
+OP_CHECKSIGADD = CScriptOp(0xba)
 
 OP_INVALIDOPCODE = CScriptOp(0xff)
 
@@ -359,10 +365,7 @@ OPCODE_NAMES.update({
     OP_NOP8: 'OP_NOP8',
     OP_NOP9: 'OP_NOP9',
     OP_NOP10: 'OP_NOP10',
-    OP_SMALLINTEGER: 'OP_SMALLINTEGER',
-    OP_PUBKEYS: 'OP_PUBKEYS',
-    OP_PUBKEYHASH: 'OP_PUBKEYHASH',
-    OP_PUBKEY: 'OP_PUBKEY',
+    OP_CHECKSIGADD: 'OP_CHECKSIGADD',
     OP_INVALIDOPCODE: 'OP_INVALIDOPCODE',
 })
 
@@ -593,6 +596,7 @@ class CScript(bytes):
         return n
 
 
+SIGHASH_DEFAULT = 0 # Taproot-only default, semantics same as SIGHASH_ALL
 SIGHASH_ALL = 1
 SIGHASH_NONE = 2
 SIGHASH_SINGLE = 3
@@ -615,7 +619,6 @@ def FindAndDelete(script, sig):
         r += script[last_sop_idx:]
     return CScript(r)
 
-
 def LegacySignatureHash(script, txTo, inIdx, hashtype):
     """Consensus-correct SignatureHash
 
@@ -738,3 +741,113 @@ class TestFrameworkScript(unittest.TestCase):
         values = [0, 1, -1, -2, 127, 128, -255, 256, (1 << 15) - 1, -(1 << 16), (1 << 24) - 1, (1 << 31), 1 - (1 << 32), 1 << 40, 1500, -1500]
         for value in values:
             self.assertEqual(CScriptNum.decode(CScriptNum.encode(CScriptNum(value))), value)
+
+def TaprootSignatureHash(txTo, spent_utxos, hash_type, input_index = 0, scriptpath = False, script = CScript(), codeseparator_pos = -1, annex = None, leaf_ver = LEAF_VERSION_TAPSCRIPT):
+    assert (len(txTo.vin) == len(spent_utxos))
+    assert (input_index < len(txTo.vin))
+    out_type = SIGHASH_ALL if hash_type == 0 else hash_type & 3
+    in_type = hash_type & SIGHASH_ANYONECANPAY
+    spk = spent_utxos[input_index].scriptPubKey
+    ss = bytes([0, hash_type]) # epoch, hash_type
+    ss += struct.pack("<i", txTo.nVersion)
+    ss += struct.pack("<I", txTo.nLockTime)
+    if in_type != SIGHASH_ANYONECANPAY:
+        ss += sha256(b"".join(i.prevout.serialize() for i in txTo.vin))
+        ss += sha256(b"".join(struct.pack("<q", u.nValue) for u in spent_utxos))
+        ss += sha256(b"".join(ser_string(u.scriptPubKey) for u in spent_utxos))
+        ss += sha256(b"".join(struct.pack("<I", i.nSequence) for i in txTo.vin))
+    if out_type == SIGHASH_ALL:
+        ss += sha256(b"".join(o.serialize() for o in txTo.vout))
+    spend_type = 0
+    if annex is not None:
+        spend_type |= 1
+    if (scriptpath):
+        spend_type |= 2
+    ss += bytes([spend_type])
+    if in_type == SIGHASH_ANYONECANPAY:
+        ss += txTo.vin[input_index].prevout.serialize()
+        ss += struct.pack("<q", spent_utxos[input_index].nValue)
+        ss += ser_string(spk)
+        ss += struct.pack("<I", txTo.vin[input_index].nSequence)
+    else:
+        ss += struct.pack("<I", input_index)
+    if (spend_type & 1):
+        ss += sha256(ser_string(annex))
+    if out_type == SIGHASH_SINGLE:
+        if input_index < len(txTo.vout):
+            ss += sha256(txTo.vout[input_index].serialize())
+        else:
+            ss += bytes(0 for _ in range(32))
+    if (scriptpath):
+        ss += TaggedHash("TapLeaf", bytes([leaf_ver]) + ser_string(script))
+        ss += bytes([0])
+        ss += struct.pack("<i", codeseparator_pos)
+    assert len(ss) ==  175 - (in_type == SIGHASH_ANYONECANPAY) * 49 - (out_type != SIGHASH_ALL and out_type != SIGHASH_SINGLE) * 32 + (annex is not None) * 32 + scriptpath * 37
+    return TaggedHash("TapSighash", ss)
+
+def taproot_tree_helper(scripts):
+    if len(scripts) == 0:
+        return ([], bytes(0 for _ in range(32)))
+    if len(scripts) == 1:
+        # One entry: treat as a leaf
+        script = scripts[0]
+        assert(not callable(script))
+        if isinstance(script, list):
+            return taproot_tree_helper(script)
+        assert(isinstance(script, tuple))
+        version = LEAF_VERSION_TAPSCRIPT
+        name = script[0]
+        code = script[1]
+        if len(script) == 3:
+            version = script[2]
+        assert version & 1 == 0
+        assert isinstance(code, bytes)
+        h = TaggedHash("TapLeaf", bytes([version]) + ser_string(code))
+        if name is None:
+            return ([], h)
+        return ([(name, version, code, bytes())], h)
+    elif len(scripts) == 2 and callable(scripts[1]):
+        # Two entries, and the right one is a function
+        left, left_h = taproot_tree_helper(scripts[0:1])
+        right_h = scripts[1](left_h)
+        left = [(name, version, script, control + right_h) for name, version, script, control in left]
+        right = []
+    else:
+        # Two or more entries: descend into each side
+        split_pos = len(scripts) // 2
+        left, left_h = taproot_tree_helper(scripts[0:split_pos])
+        right, right_h = taproot_tree_helper(scripts[split_pos:])
+        left = [(name, version, script, control + right_h) for name, version, script, control in left]
+        right = [(name, version, script, control + left_h) for name, version, script, control in right]
+    if right_h < left_h:
+        right_h, left_h = left_h, right_h
+    h = TaggedHash("TapBranch", left_h + right_h)
+    return (left + right, h)
+
+TaprootInfo = namedtuple("TaprootInfo", "scriptPubKey,inner_pubkey,negflag,tweak,leaves")
+TaprootLeafInfo = namedtuple("TaprootLeafInfo", "script,version,merklebranch")
+
+def taproot_construct(pubkey, scripts=None):
+    """Construct a tree of Taproot spending conditions
+
+    pubkey: an ECPubKey object for the internal pubkey
+    scripts: a list of items; each item is either:
+             - a (name, CScript) tuple
+             - a (name, CScript, leaf version) tuple
+             - another list of items (with the same structure)
+             - a function, which specifies how to compute the hashing partner
+               in function of the hash of whatever it is combined with
+
+    Returns: script (sPK or redeemScript), tweak, {name:(script, leaf version, negation flag, innerkey, merklepath), ...}
+    """
+    if scripts is None:
+        scripts = []
+
+    ret, h = taproot_tree_helper(scripts)
+    tweak = TaggedHash("TapTweak", pubkey + h)
+    tweaked, negated = tweak_add_pubkey(pubkey, tweak)
+    leaves = dict((name, TaprootLeafInfo(script, version, merklebranch)) for name, version, script, merklebranch in ret)
+    return TaprootInfo(CScript([OP_1, tweaked]), pubkey, negated + 0, tweak, leaves)
+
+def is_op_success(o):
+    return o == 0x50 or o == 0x62 or o == 0x89 or o == 0x8a or o == 0x8d or o == 0x8e or (o >= 0x7e and o <= 0x81) or (o >= 0x83 and o <= 0x86) or (o >= 0x95 and o <= 0x99) or (o >= 0xbb and o <= 0xfe)
diff --git a/test/functional/test_runner.py b/test/functional/test_runner.py
index b109480a59..ed6e830bb9 100755
--- a/test/functional/test_runner.py
+++ b/test/functional/test_runner.py
@@ -107,6 +107,7 @@ BASE_SCRIPTS = [
     'mempool_updatefromblock.py',
     'wallet_dump.py',
     'wallet_listtransactions.py',
+    'feature_taproot.py',
     # vv Tests less than 60s vv
     'p2p_sendheaders.py',
     'wallet_importmulti.py',