Migrate pytest to unittest

After a discussion in the core developers channel, we have decided to
migrate from `pytest` to `unittest` as the testing framework. This
commit sets up the repository to use `unittest` and migrates the
first couple of tests files to the new framework.

What I have done to migrate to `unitest`:

- Removed all `pytest` test files, since they are incompatible.

- Removed `pytest`-related dependencies from the Pipfile.

- Added `coverage.py` to the Pipfile dev-packages and relocked.

- Added convenience scripts to Pipfile for running the test suite.

- Adjust to `azure-pipelines.yml` to use `coverage.py` and `unittest`.

- Migrated four test files from `pytest` to `unittest` format.

In addition, I've added five helper Mock subclasses in `helpers.py`
and created a `TestCase` subclass in `base.py` to add an assertion
that asserts that no log records were logged within the context of
the context manager. Obviously, these new utility functions and
classes are fully tested in their respective `test_` files.

Finally, I've started with an introductory guide for writing tests
for our bot in `README.md`.

8 files changed, 0 insertions, 600 deletions

diff --git a/tests/cogs/__init__.py b/tests/cogs/__init__.py
deleted file mode 100644
index e69de29bb..000000000
--- a/tests/cogs/__init__.py
+++ /dev/null
diff --git a/tests/cogs/sync/__init__.py b/tests/cogs/sync/__init__.py
deleted file mode 100644
index e69de29bb..000000000
--- a/tests/cogs/sync/__init__.py
+++ /dev/null
diff --git a/tests/cogs/sync/test_roles.py b/tests/cogs/sync/test_roles.py
deleted file mode 100644
index c561ba447..000000000
--- a/tests/cogs/sync/test_roles.py
+++ /dev/null
@@ -1,103 +0,0 @@
-from bot.cogs.sync.syncers import Role, get_roles_for_sync
-
-
-def test_get_roles_for_sync_empty_return_for_equal_roles():
-    api_roles = {Role(id=41, name='name', colour=33, permissions=0x8, position=1)}
-    guild_roles = {Role(id=41, name='name', colour=33, permissions=0x8, position=1)}
-
-    assert get_roles_for_sync(guild_roles, api_roles) == (set(), set(), set())
-
-
-def test_get_roles_for_sync_returns_roles_to_update_with_non_id_diff():
-    api_roles = {Role(id=41, name='old name', colour=35, permissions=0x8, position=1)}
-    guild_roles = {Role(id=41, name='new name', colour=33, permissions=0x8, position=2)}
-
-    assert get_roles_for_sync(guild_roles, api_roles) == (
-        set(),
-        guild_roles,
-        set(),
-    )
-
-
-def test_get_roles_only_returns_roles_that_require_update():
-    api_roles = {
-        Role(id=41, name='old name', colour=33, permissions=0x8, position=1),
-        Role(id=53, name='other role', colour=55, permissions=0, position=3)
-    }
-    guild_roles = {
-        Role(id=41, name='new name', colour=35, permissions=0x8, position=2),
-        Role(id=53, name='other role', colour=55, permissions=0, position=3)
-    }
-
-    assert get_roles_for_sync(guild_roles, api_roles) == (
-        set(),
-        {Role(id=41, name='new name', colour=35, permissions=0x8, position=2)},
-        set(),
-    )
-
-
-def test_get_roles_returns_new_roles_in_first_tuple_element():
-    api_roles = {
-        Role(id=41, name='name', colour=35, permissions=0x8, position=1),
-    }
-    guild_roles = {
-        Role(id=41, name='name', colour=35, permissions=0x8, position=1),
-        Role(id=53, name='other role', colour=55, permissions=0, position=2)
-    }
-
-    assert get_roles_for_sync(guild_roles, api_roles) == (
-        {Role(id=53, name='other role', colour=55, permissions=0, position=2)},
-        set(),
-        set(),
-    )
-
-
-def test_get_roles_returns_roles_to_update_and_new_roles():
-    api_roles = {
-        Role(id=41, name='old name', colour=35, permissions=0x8, position=1),
-    }
-    guild_roles = {
-        Role(id=41, name='new name', colour=40, permissions=0x16, position=2),
-        Role(id=53, name='other role', colour=55, permissions=0, position=3)
-    }
-
-    assert get_roles_for_sync(guild_roles, api_roles) == (
-        {Role(id=53, name='other role', colour=55, permissions=0, position=3)},
-        {Role(id=41, name='new name', colour=40, permissions=0x16, position=2)},
-        set(),
-    )
-
-
-def test_get_roles_returns_roles_to_delete():
-    api_roles = {
-        Role(id=41, name='name', colour=35, permissions=0x8, position=1),
-        Role(id=61, name='to delete', colour=99, permissions=0x9, position=2),
-    }
-    guild_roles = {
-        Role(id=41, name='name', colour=35, permissions=0x8, position=1),
-    }
-
-    assert get_roles_for_sync(guild_roles, api_roles) == (
-        set(),
-        set(),
-        {Role(id=61, name='to delete', colour=99, permissions=0x9, position=2)},
-    )
-
-
-def test_get_roles_returns_roles_to_delete_update_and_new_roles():
-    api_roles = {
-        Role(id=41, name='not changed', colour=35, permissions=0x8, position=1),
-        Role(id=61, name='to delete', colour=99, permissions=0x9, position=2),
-        Role(id=71, name='to update', colour=99, permissions=0x9, position=3),
-    }
-    guild_roles = {
-        Role(id=41, name='not changed', colour=35, permissions=0x8, position=1),
-        Role(id=81, name='to create', colour=99, permissions=0x9, position=4),
-        Role(id=71, name='updated', colour=101, permissions=0x5, position=3),
-    }
-
-    assert get_roles_for_sync(guild_roles, api_roles) == (
-        {Role(id=81, name='to create', colour=99, permissions=0x9, position=4)},
-        {Role(id=71, name='updated', colour=101, permissions=0x5, position=3)},
-        {Role(id=61, name='to delete', colour=99, permissions=0x9, position=2)},
-    )
diff --git a/tests/cogs/sync/test_users.py b/tests/cogs/sync/test_users.py
deleted file mode 100644
index a863ae35b..000000000
--- a/tests/cogs/sync/test_users.py
+++ /dev/null
@@ -1,69 +0,0 @@
-from bot.cogs.sync.syncers import User, get_users_for_sync
-
-
-def fake_user(**kwargs):
-    kwargs.setdefault('id', 43)
-    kwargs.setdefault('name', 'bob the test man')
-    kwargs.setdefault('discriminator', 1337)
-    kwargs.setdefault('avatar_hash', None)
-    kwargs.setdefault('roles', (666,))
-    kwargs.setdefault('in_guild', True)
-    return User(**kwargs)
-
-
-def test_get_users_for_sync_returns_nothing_for_empty_params():
-    assert get_users_for_sync({}, {}) == (set(), set())
-
-
-def test_get_users_for_sync_returns_nothing_for_equal_users():
-    api_users = {43: fake_user()}
-    guild_users = {43: fake_user()}
-
-    assert get_users_for_sync(guild_users, api_users) == (set(), set())
-
-
-def test_get_users_for_sync_returns_users_to_update_on_non_id_field_diff():
-    api_users = {43: fake_user()}
-    guild_users = {43: fake_user(name='new fancy name')}
-
-    assert get_users_for_sync(guild_users, api_users) == (
-        set(),
-        {fake_user(name='new fancy name')}
-    )
-
-
-def test_get_users_for_sync_returns_users_to_create_with_new_ids_on_guild():
-    api_users = {43: fake_user()}
-    guild_users = {43: fake_user(), 63: fake_user(id=63)}
-
-    assert get_users_for_sync(guild_users, api_users) == (
-        {fake_user(id=63)},
-        set()
-    )
-
-
-def test_get_users_for_sync_updates_in_guild_field_on_user_leave():
-    api_users = {43: fake_user(), 63: fake_user(id=63)}
-    guild_users = {43: fake_user()}
-
-    assert get_users_for_sync(guild_users, api_users) == (
-        set(),
-        {fake_user(id=63, in_guild=False)}
-    )
-
-
-def test_get_users_for_sync_updates_and_creates_users_as_needed():
-    api_users = {43: fake_user()}
-    guild_users = {63: fake_user(id=63)}
-
-    assert get_users_for_sync(guild_users, api_users) == (
-        {fake_user(id=63)},
-        {fake_user(in_guild=False)}
-    )
-
-
-def test_get_users_for_sync_does_not_duplicate_update_users():
-    api_users = {43: fake_user(in_guild=False)}
-    guild_users = {}
-
-    assert get_users_for_sync(guild_users, api_users) == (set(), set())
diff --git a/tests/cogs/test_antispam.py b/tests/cogs/test_antispam.py
deleted file mode 100644
index 67900b275..000000000
--- a/tests/cogs/test_antispam.py
+++ /dev/null
@@ -1,30 +0,0 @@
-import pytest
-
-from bot.cogs import antispam
-
-
-def test_default_antispam_config_is_valid():
-    validation_errors = antispam.validate_config()
-    assert not validation_errors
-
-
[email protected](
-    ('config', 'expected'),
-    (
-        (
-            {'invalid-rule': {}},
-            {'invalid-rule': "`invalid-rule` is not recognized as an antispam rule."}
-        ),
-        (
-            {'burst': {'interval': 10}},
-            {'burst': "Key `max` is required but not set for rule `burst`"}
-        ),
-        (
-            {'burst': {'max': 10}},
-            {'burst': "Key `interval` is required but not set for rule `burst`"}
-        )
-    )
-)
-def test_invalid_antispam_config_returns_validation_errors(config, expected):
-    validation_errors = antispam.validate_config(config)
-    assert validation_errors == expected
diff --git a/tests/cogs/test_information.py b/tests/cogs/test_information.py
deleted file mode 100644
index 184bd2595..000000000
--- a/tests/cogs/test_information.py
+++ /dev/null
@@ -1,211 +0,0 @@
-import asyncio
-import logging
-import textwrap
-from datetime import datetime
-from unittest.mock import MagicMock, patch
-
-import pytest
-from discord import (
-    CategoryChannel,
-    Colour,
-    Permissions,
-    Role,
-    TextChannel,
-    VoiceChannel,
-)
-
-from bot.cogs import information
-from bot.constants import Emojis
-from bot.decorators import InChannelCheckFailure
-from tests.helpers import AsyncMock
-
-
[email protected]()
-def cog(simple_bot):
-    return information.Information(simple_bot)
-
-
-def role(name: str, id_: int):
-    r = MagicMock()
-    r.name = name
-    r.id = id_
-    r.mention = f'&{name}'
-    return r
-
-
-def member(status: str):
-    m = MagicMock()
-    m.status = status
-    return m
-
-
[email protected]()
-def ctx(moderator_role, simple_ctx):
-    simple_ctx.author.roles = [moderator_role]
-    simple_ctx.guild.created_at = datetime(2001, 1, 1)
-    simple_ctx.send = AsyncMock()
-    return simple_ctx
-
-
-def test_roles_info_command(cog, ctx):
-    everyone_role = MagicMock()
-    everyone_role.name = '@everyone'  # should be excluded in the output
-    ctx.author.roles.append(everyone_role)
-    ctx.guild.roles = ctx.author.roles
-
-    cog.roles_info.can_run = AsyncMock()
-    cog.roles_info.can_run.return_value = True
-
-    coroutine = cog.roles_info.callback(cog, ctx)
-
-    assert asyncio.run(coroutine) is None  # no rval
-    ctx.send.assert_called_once()
-    _, kwargs = ctx.send.call_args
-    embed = kwargs.pop('embed')
-    assert embed.title == "Role information"
-    assert embed.colour == Colour.blurple()
-    assert embed.description == f"`{ctx.guild.roles[0].id}` - {ctx.guild.roles[0].mention}\n"
-    assert embed.footer.text == "Total roles: 1"
-
-
-def test_role_info_command(cog, ctx):
-    dummy_role = MagicMock(spec=Role)
-    dummy_role.name = "Dummy"
-    dummy_role.colour = Colour.blurple()
-    dummy_role.id = 112233445566778899
-    dummy_role.position = 10
-    dummy_role.permissions = Permissions(0)
-    dummy_role.members = [ctx.author]
-
-    admin_role = MagicMock(spec=Role)
-    admin_role.name = "Admin"
-    admin_role.colour = Colour.red()
-    admin_role.id = 998877665544332211
-    admin_role.position = 3
-    admin_role.permissions = Permissions(0)
-    admin_role.members = [ctx.author]
-
-    ctx.guild.roles = [dummy_role, admin_role]
-
-    cog.role_info.can_run = AsyncMock()
-    cog.role_info.can_run.return_value = True
-
-    coroutine = cog.role_info.callback(cog, ctx, dummy_role, admin_role)
-
-    assert asyncio.run(coroutine) is None
-
-    assert ctx.send.call_count == 2
-
-    (_, dummy_kwargs), (_, admin_kwargs) = ctx.send.call_args_list
-
-    dummy_embed = dummy_kwargs["embed"]
-    admin_embed = admin_kwargs["embed"]
-
-    assert dummy_embed.title == "Dummy info"
-    assert dummy_embed.colour == Colour.blurple()
-
-    assert dummy_embed.fields[0].value == str(dummy_role.id)
-    assert dummy_embed.fields[1].value == f"#{dummy_role.colour.value:0>6x}"
-    assert dummy_embed.fields[2].value == "0.63 0.48 218"
-    assert dummy_embed.fields[3].value == "1"
-    assert dummy_embed.fields[4].value == "10"
-    assert dummy_embed.fields[5].value == "0"
-
-    assert admin_embed.title == "Admin info"
-    assert admin_embed.colour == Colour.red()
-
-# There is no argument passed in here that we can use to test,
-# so the return value would change constantly.
-@patch('bot.cogs.information.time_since')
-def test_server_info_command(time_since_patch, cog, ctx, moderator_role):
-    time_since_patch.return_value = '2 days ago'
-
-    ctx.guild.created_at = datetime(2001, 1, 1)
-    ctx.guild.features = ('lemons', 'apples')
-    ctx.guild.region = 'The Moon'
-    ctx.guild.roles = [moderator_role]
-    ctx.guild.channels = [
-        TextChannel(
-            state={},
-            guild=ctx.guild,
-            data={'id': 42, 'name': 'lemons-offering', 'position': 22, 'type': 'text'}
-        ),
-        CategoryChannel(
-            state={},
-            guild=ctx.guild,
-            data={'id': 5125, 'name': 'the-lemon-collection', 'position': 22, 'type': 'category'}
-        ),
-        VoiceChannel(
-            state={},
-            guild=ctx.guild,
-            data={'id': 15290, 'name': 'listen-to-lemon', 'position': 22, 'type': 'voice'}
-        )
-    ]
-    ctx.guild.members = [
-        member('online'), member('online'),
-        member('idle'),
-        member('dnd'), member('dnd'), member('dnd'), member('dnd'),
-        member('offline'), member('offline'), member('offline')
-    ]
-    ctx.guild.member_count = 1_234
-    ctx.guild.icon_url = 'a-lemon.png'
-
-    coroutine = cog.server_info.callback(cog, ctx)
-    assert asyncio.run(coroutine) is None  # no rval
-
-    time_since_patch.assert_called_once_with(ctx.guild.created_at, precision='days')
-    _, kwargs = ctx.send.call_args
-    embed = kwargs.pop('embed')
-    assert embed.colour == Colour.blurple()
-    assert embed.description == textwrap.dedent(f"""
-        **Server information**
-        Created: {time_since_patch.return_value}
-        Voice region: {ctx.guild.region}
-        Features: {', '.join(ctx.guild.features)}
-
-        **Counts**
-        Members: {ctx.guild.member_count:,}
-        Roles: {len(ctx.guild.roles)}
-        Text: 1
-        Voice: 1
-        Channel categories: 1
-
-        **Members**
-        {Emojis.status_online} 2
-        {Emojis.status_idle} 1
-        {Emojis.status_dnd} 4
-        {Emojis.status_offline} 3
-        """)
-    assert embed.thumbnail.url == 'a-lemon.png'
-
-
-def test_user_info_on_other_users_from_non_moderator(ctx, cog):
-    ctx.author = MagicMock()
-    ctx.author.__eq__.return_value = False
-    ctx.author.roles = []
-    coroutine = cog.user_info.callback(cog, ctx, user='scragly')  # skip checks, pass args
-
-    assert asyncio.run(coroutine) is None  # no rval
-    ctx.send.assert_called_once_with(
-        "You may not use this command on users other than yourself."
-    )
-
-
-def test_user_info_in_wrong_channel_from_non_moderator(ctx, cog):
-    ctx.author = MagicMock()
-    ctx.author.__eq__.return_value = False
-    ctx.author.roles = []
-
-    coroutine = cog.user_info.callback(cog, ctx)
-    message = 'Sorry, but you may only use this command within <#267659945086812160>.'
-    with pytest.raises(InChannelCheckFailure, match=message):
-        assert asyncio.run(coroutine) is None  # no rval
-
-
-def test_setup(simple_bot, caplog):
-    information.setup(simple_bot)
-    simple_bot.add_cog.assert_called_once()
-    [record] = caplog.records
-
-    assert record.message == "Cog loaded: Information"
-    assert record.levelno == logging.INFO
diff --git a/tests/cogs/test_security.py b/tests/cogs/test_security.py
deleted file mode 100644
index 1efb460fe..000000000
--- a/tests/cogs/test_security.py
+++ /dev/null
@@ -1,54 +0,0 @@
-import logging
-from unittest.mock import MagicMock
-
-import pytest
-from discord.ext.commands import NoPrivateMessage
-
-from bot.cogs import security
-
-
[email protected]()
-def cog():
-    bot = MagicMock()
-    return security.Security(bot)
-
-
[email protected]()
-def context():
-    return MagicMock()
-
-
-def test_check_additions(cog):
-    cog.bot.check.assert_any_call(cog.check_on_guild)
-    cog.bot.check.assert_any_call(cog.check_not_bot)
-
-
-def test_check_not_bot_for_humans(cog, context):
-    context.author.bot = False
-    assert cog.check_not_bot(context)
-
-
-def test_check_not_bot_for_robots(cog, context):
-    context.author.bot = True
-    assert not cog.check_not_bot(context)
-
-
-def test_check_on_guild_outside_of_guild(cog, context):
-    context.guild = None
-
-    with pytest.raises(NoPrivateMessage, match="This command cannot be used in private messages."):
-        cog.check_on_guild(context)
-
-
-def test_check_on_guild_on_guild(cog, context):
-    context.guild = "lemon's lemonade stand"
-    assert cog.check_on_guild(context)
-
-
-def test_security_cog_load(caplog):
-    bot = MagicMock()
-    security.setup(bot)
-    bot.add_cog.assert_called_once()
-    [record] = caplog.records
-    assert record.message == "Cog loaded: Security"
-    assert record.levelno == logging.INFO
diff --git a/tests/cogs/test_token_remover.py b/tests/cogs/test_token_remover.py
deleted file mode 100644
index 9d46b3a05..000000000
--- a/tests/cogs/test_token_remover.py
+++ /dev/null
@@ -1,133 +0,0 @@
-import asyncio
-from unittest.mock import MagicMock
-
-import pytest
-from discord import Colour
-
-from bot.cogs.token_remover import (
-    DELETION_MESSAGE_TEMPLATE,
-    TokenRemover,
-    setup as setup_cog,
-)
-from bot.constants import Channels, Colours, Event, Icons
-from tests.helpers import AsyncMock
-
-
[email protected]()
-def token_remover():
-    bot = MagicMock()
-    bot.get_cog.return_value = MagicMock()
-    bot.get_cog.return_value.send_log_message = AsyncMock()
-    return TokenRemover(bot=bot)
-
-
[email protected]()
-def message():
-    message = MagicMock()
-    message.author.__str__.return_value = 'lemon'
-    message.author.bot = False
-    message.author.avatar_url_as.return_value = 'picture-lemon.png'
-    message.author.id = 42
-    message.author.mention = '@lemon'
-    message.channel.send = AsyncMock()
-    message.channel.mention = '#lemonade-stand'
-    message.content = ''
-    message.delete = AsyncMock()
-    message.id = 555
-    return message
-
-
[email protected](
-    ('content', 'expected'),
-    (
-        ('MTIz', True),  # 123
-        ('YWJj', False),  # abc
-    )
-)
-def test_is_valid_user_id(content: str, expected: bool):
-    assert TokenRemover.is_valid_user_id(content) is expected
-
-
[email protected](
-    ('content', 'expected'),
-    (
-        ('DN9r_A', True),  # stolen from dapi, thanks to the author of the 'token' tag!
-        ('MTIz', False),  # 123
-    )
-)
-def test_is_valid_timestamp(content: str, expected: bool):
-    assert TokenRemover.is_valid_timestamp(content) is expected
-
-
-def test_mod_log_property(token_remover):
-    token_remover.bot.get_cog.return_value = 'lemon'
-    assert token_remover.mod_log == 'lemon'
-    token_remover.bot.get_cog.assert_called_once_with('ModLog')
-
-
-def test_ignores_bot_messages(token_remover, message):
-    message.author.bot = True
-    coroutine = token_remover.on_message(message)
-    assert asyncio.run(coroutine) is None
-
-
[email protected]('content', ('', 'lemon wins'))
-def test_ignores_messages_without_tokens(token_remover, message, content):
-    message.content = content
-    coroutine = token_remover.on_message(message)
-    assert asyncio.run(coroutine) is None
-
-
[email protected]('content', ('foo.bar.baz', 'x.y.'))
-def test_ignores_invalid_tokens(token_remover, message, content):
-    message.content = content
-    coroutine = token_remover.on_message(message)
-    assert asyncio.run(coroutine) is None
-
-
[email protected](
-    'content, censored_token',
-    (
-        ('MTIz.DN9R_A.xyz', 'MTIz.DN9R_A.xxx'),
-    )
-)
-def test_censors_valid_tokens(
-    token_remover, message, content, censored_token, caplog
-):
-    message.content = content
-    coroutine = token_remover.on_message(message)
-    assert asyncio.run(coroutine) is None  # still no rval
-
-    # asyncio logs some stuff about its reactor, discard it
-    [_, record] = caplog.records
-    assert record.message == (
-        "Censored a seemingly valid token sent by lemon (`42`) in #lemonade-stand, "
-        f"token was `{censored_token}`"
-    )
-
-    message.delete.assert_called_once_with()
-    message.channel.send.assert_called_once_with(
-        DELETION_MESSAGE_TEMPLATE.format(mention='@lemon')
-    )
-    token_remover.bot.get_cog.assert_called_with('ModLog')
-    message.author.avatar_url_as.assert_called_once_with(static_format='png')
-
-    mod_log = token_remover.bot.get_cog.return_value
-    mod_log.ignore.assert_called_once_with(Event.message_delete, message.id)
-    mod_log.send_log_message.assert_called_once_with(
-        icon_url=Icons.token_removed,
-        colour=Colour(Colours.soft_red),
-        title="Token removed!",
-        text=record.message,
-        thumbnail='picture-lemon.png',
-        channel_id=Channels.mod_alerts
-    )
-
-
-def test_setup(caplog):
-    bot = MagicMock()
-    setup_cog(bot)
-    [record] = caplog.records
-
-    bot.add_cog.assert_called_once()
-    assert record.message == "Cog loaded: TokenRemover"