Testing behavior, not implementation details – Testing Behavior

models.py

# behavior/models.py
from dataclasses import dataclass
from enum import Enum


class TaskStatus(str, Enum):
    OPEN = "OPEN"
    CLOSED = "CLOSED"


@dataclass
class Task:
    title: str
    status: TaskStatus

store.py

# behavior/store.py

import sqlite3
from abc import ABC

from behavior.models import Task, TaskStatus


class TaskStore(ABC):
    def add_task(self, task: Task) -> None:
        raise NotImplementedError

    def list_tasks(self) -> list[Task]:
        raise NotImplementedError


class TaskStoreSQLite(TaskStore):
    def __init__(self, connection: sqlite3.Connection):
        self._connection = connection

    def add_task(self, task: Task) -> None:
        self._connection.execute(
            "INSERT INTO tasks (title, status) VALUES (?, ?)",
            (task.title, task.status.name),
        )

    def list_tasks(self) -> list[Task]:
        cursor = self._connection.execute("SELECT title, status FROM tasks")
        return [Task(title, TaskStatus(status)) for title, status in cursor.fetchall()]

tests.py

# behavior/tests.py
import sqlite3

import pytest

from behavior.models import Task, TaskStatus
from behavior.store import TaskStoreInMemory, TaskStoreSQLite


@pytest.fixture
def connection(tmp_path) -> sqlite3.Connection:
    connection = sqlite3.connect(tmp_path / "test.db")
    connection.execute("CREATE TABLE tasks (title TEXT, status TEXT)")
    return connection


@pytest.fixture
def store(connection) -> TaskStoreSQLite:
    return TaskStoreSQLite(connection)


def test_added_task_listed(store: TaskStoreSQLite):
    task = Task(title="Do the dishes", status=TaskStatus.OPEN)

    store.add_task(task)

    assert store.list_tasks() == [task]