Introduction to pytest: A Beginner's Guide (https://youtu.be/Kt6QqGoAlvI)

reply.py

import datetime


class Reply:
    def __init__(self, body: str, user: str, created: datetime.datetime) -> None:
        self.body = body
        self.user = user
        self.created = created
    
    def __repr__(self) -> str:
        return f"<Reply from '{self.user}' on '{self.created.strftime('%Y-%m-%d %H:%M')}'>"

    def __eq__(self, __value: object) -> bool:
        if not isinstance(__value, Reply):
            return False
        return (
            self.body == __value.body and
            self.user == __value.user and
            self.created == __value.created
        )

test_reply.py

import datetime

import pytest
from reply import Reply


def test_init():
    body = "Hello, World!"
    user = "user1"
    created = datetime.datetime.now()

    reply = Reply(body, user, created)

    assert reply.body == body
    assert reply.user == user
    assert reply.created == created


def test_repr():
    body = "Hello, World!"
    user = "user1"
    created = datetime.datetime(2023, 1, 1, 0, 0, 0)

    reply = Reply(body, user, created)
    expected_repr = f"<Reply from '{user}' on '2023-01-01 00:00'>"

    assert repr(reply) == expected_repr


def test_repr_without_date():
    body = "Hello, World!"
    user = "user1"
    created = "2021-02-07 12:00"

    reply = Reply(body, user, created)

    with pytest.raises(AttributeError):
        assert repr(reply) == f"<Reply from '{user}' on '2021-02-07 12:00'>"


def test_eq_same_values():
    body = "Hello, World!"
    user = "user1"
    created = datetime.datetime.now()

    reply1 = Reply(body, user, created)
    reply2 = Reply(body, user, created)

    assert reply1 == reply2


def test_eq_different_values():
    body1 = "Hello, World!"
    user1 = "user1"
    created1 = datetime.datetime.now()

    body2 = "Goodbye, World!"
    user2 = "user2"
    created2 = created1 + datetime.timedelta(minutes=1)

    reply1 = Reply(body1, user1, created1)
    reply2 = Reply(body2, user2, created2)

    assert reply1 != reply2


def test_eq_different_types():
    body = "Hello, World!"
    user = "user1"
    created = datetime.datetime.now()

    reply = Reply(body, user, created)
    non_reply = "Not a reply object"

    assert reply != non_reply

test_simple.py

# import os
import pytest


def test_simple_add():
	assert 1 + 1 == 2


# @pytest.mark.xfail
# @pytest.mark.skip
# @pytest.mark.skipif(os.name == "posix", reason="does not work on mac")
def test_failing():
    assert 'a' == 'b'

test_thread.py

import datetime

import pytest
from reply import Reply
from thread import Thread


@pytest.fixture
def thread():
    """This fixture returns a Thread object"""
    title = "Hello, World!"
    user = "user1"
    replies = [
        Reply("Hello, World!", "user1", datetime.datetime(2023, 1, 1, 0, 0, 0)),
        Reply("Goodbye, World!", "user2", datetime.datetime(2023, 1, 2, 0, 0, 0)),
    ]
    return Thread(title, user, replies)


def test_init():
    title = "Hello, World!"
    user = "user1"
    replies = [
        Reply("Hello, World!", "user1", datetime.datetime(2023, 1, 1, 0, 0, 0)),
        Reply("Goodbye, World!", "user2", datetime.datetime(2023, 1, 2, 0, 0, 0)),
    ]

    thread = Thread(title, user, replies)

    assert thread.title == "Hello, World!"
    assert thread.user == "user1"
    assert thread.replies == replies


def test_repr(thread):
    assert repr(thread) == "<Thread 'Hello, World!' by 'user1'>"


def test_reply(thread):
    new_reply = Reply("Hello, World!", "user1", datetime.datetime(2023, 1, 3, 0, 0, 0))

    thread.reply(new_reply)

    assert new_reply in thread.replies


def test_reply_more_recent(thread):
    new_reply = Reply("Hello, World!", "user1", datetime.datetime(2023, 1, 1, 0, 0, 0))

    with pytest.raises(ValueError):
        thread.reply(new_reply)

thread.py

from reply import Reply


class Thread:
    def __init__(self, title: str, user: str, replies: list[Reply] = None) -> None:
        self.title = title
        self.user = user
        self.replies = replies or []
    
    def __repr__(self) -> str:
        return f"<Thread '{self.title}' by '{self.user}'>"
    
    def reply(self, reply: Reply) -> None:
        if reply.created < self.replies[-1].created:
            raise ValueError("New reply is older than the last reply")
        self.replies.append(reply)