montest

A stochastic testing framework for Python designed to test non-deterministic systems by evaluating statistical evidence across repeated observations instead of relying on one-shot binary assertions.

Core install

pip install montest

The base install ships the core stochastic engine only and has no runtime dependencies.

Quick start

import math
import random

from montest import Decision, SequentialIterator, sprt


def bernoulli_llr(value: int) -> float:
    return math.log(0.6 / 0.3) if value else math.log(0.4 / 0.7)


rng = random.Random(42)
criterion = sprt(llr=bernoulli_llr, alpha=0.05, beta=0.10)

for sample in SequentialIterator(lambda: int(rng.random() < 0.6), criterion):
    print(sample.index, sample.value, sample.decision.value)
    if sample.decision is not Decision.CONTINUE:
        break

Future testing-tool integrations are intended to live behind optional install groups such as montest[pytest] and montest[behave]; this release only ships the zero-dependency core.

Documentation

Build local documentation with:

task docs

Development Setup

Prerequisites (without Nix)

You will need the following tools installed on your system:

• Python 3.11, 3.12, 3.13, and 3.14 — all four versions must be discoverable on $PATH as python3.11, python3.12, python3.13, and python3.14
• uv — fast Python package and project manager
• Task (go-task) — task runner used to execute all CI steps

Once the tools are available, install the project dependencies:

task sync

Then you can run the individual workflow steps:

task lint        # ruff linter
task typecheck   # mypy type checker
task test        # run tests with the default tox env (py311)
task test TOX_ENV=py313  # run tests against a specific Python version

Prerequisites (with Nix)

If you have Nix with flakes enabled, all required tools are provided automatically by the dev shell — no manual installation needed:

nix develop

This drops you into a shell that has uv, task, and Python 3.11–3.14 all ready to use. The same task commands above apply once you are inside the dev shell.

License

Copyright 2026 Banco Bilbao Vizcaya Argentaria, S.A.

Licensed under the Apache License, Version 2.0. See the NOTICE file for additional attribution information.