Guará

Guará is a Python framework for business logic expression. It allows you to write production code and tests as executable domain language, combining:

• Business Logic Language → expresses domain behavior using Ubiquitous Language (DDD)
• Test Framework → orchestrates scenarios using Given / When / Then

Instead of focusing only on technical assertions, Guará enables you to describe business scenarios as code, making production code and tests readable by developers and domain experts.

Core Idea

Guará turns code into business narratives:

• Transactions → represent actions (use cases)
• Assertions (it) → represent business expectations
• Application DSL → orchestrates flows in domain language

Syntax

Application.when(DoSomething [,with_parameter=value, ...]).expects(it.Matches, a_condition)

Example in Action

Modeling

from guara.application import Application
from guara import it
from transactions import HasBalance, BuyAsset, UpdatePortfolio


def main():
    finance_app = Application()
    (
        finance_app.given(HasBalance)
        .when(BuyAsset, symbol="AAPL", amount=2000)
        .and_(UpdatePortfolio)
        .expects(it.IsEqualTo, 20)
    )

UI Testing

from guara.application import Application
from guara import it
from selenium import webdriver
from transactions import OpenApp, ChangeToPortuguese, NavigateToInfoPage, CloseApp


def test_sample_web_page():
    app = Application(webdriver.Chrome())
    app.given(OpenApp, url="https://anyhost.com/")
    app.when(ChangeToPortuguese).expects(it.IsEqualTo, CONTENT_IN_PORTUGUESE)
    app.when(NavigateToInfoPage).then(it.Contains, "This project was born")
    app.execute(CloseApp)

Documentation

For more information, check: https://guara.readthedocs.io/en/latest/