claude-dev-suite Property-Based Testing
Test that properties (universal invariants) hold for all inputs, not just specific examples.
Properties for Bitcoin
Common properties:
- Round-trip:
decode(encode(x)) == xfor tx, script, address, descriptor, PSBT. - Sigops cost of any script ≤ static analysis bound.
- Miniscript satisfaction of any policy produces a valid script.
- Descriptor checksum is preserved through canonical encoding.
- Hash determinism:
H(x) == H(x)always; consistent across serialization.
Rust (proptest)
use proptest::prelude::*;
proptest! {
#[test]
fn tx_roundtrip(tx in any_tx()) {
let encoded = tx.consensus_encode_to_vec();
let decoded = Transaction::consensus_decode(&mut &encoded[..]).unwrap();
prop_assert_eq!(tx, decoded);
}
}
Rust (quickcheck)
#[quickcheck]
fn descriptor_checksum_invariant(desc: ValidDescriptor) -> bool {
let s = desc.to_string();
let with_checksum = with_checksum(&s);
parse(&with_checksum).is_ok()
}
Python (hypothesis)
from hypothesis import given, strategies as st
@given(st.binary(min_size=1, max_size=520))
def test_script_roundtrip(data):
s = Script(data)
assert Script(bytes(s)) == s
Coverage strategies
- Custom strategies for valid Bitcoin objects (txs with valid inputs/outputs, valid scripts, valid descriptors).
- Shrinking — when a counterexample is found, hypothesis/proptest reduce it to minimum failing case.
Compared to example-based
| Aspect | Example tests | Property-based |
|---|---|---|
| Coverage | known cases | random + edge |
| Setup effort | low | medium (writing strategies) |
| Bug discovery | misses unknowns | finds unknowns |
| Failure repro | trivial | needs shrinking |
Use cases
- Parser tests for tx, script, descriptor, PSBT.
- Crypto roundtrip for Schnorr / ECDSA / sighash.
- Mempool policy invariants: any tx accepted must satisfy X.
Common issues
- Custom strategies hard to get right (don't accidentally exclude important cases).
- Slow if too many runs; tune with
proptest_config!(). - Shrinking can give surprising results — verify the shrunk case actually triggers the bug.