Testing behavior, not implementation details – Testing implementation Details

models.py

# implementation_details/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

# implementation_details/store.py
import sqlite3

from implementation_details.models import Task, TaskStatus


class TaskStoreSQLite:

    def add_task(self, connection: sqlite3.Connection, task):
        connection.execute(
            "INSERT INTO tasks (title, status) VALUES (?, ?)",
            (task.title, task.status.name),
        )

    def list_tasks(self, connection: sqlite3.Connection,):
        cursor = connection.execute("SELECT title, status FROM tasks")
        return [Task(title, TaskStatus(status)) for title, status in cursor.fetchall()]

tests.py

# implementation_details/tests.py
import sqlite3

import pytest

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


@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


def test_add_task(connection: sqlite3.Connection):
    store = TaskStoreSQLite()
    task = Task(title="Do the dishes", status=TaskStatus.OPEN)

    store.add_task(connection, task)

    task_row = connection.execute("SELECT title, status FROM tasks").fetchone()
    assert task_row[0] == "Do the dishes"
    assert task_row[1] == "OPEN"


def test_list_tasks(connection: sqlite3.Connection):
    connection.execute("INSERT INTO tasks (title, status) VALUES ('Do the dishes', 'OPEN')")
    store = TaskStoreSQLite()

    assert store.list_tasks(connection) == [Task(title="Do the dishes", status=TaskStatus.OPEN)]