Merge branch 'master' into mod-utils-tests

11 files changed, 586 insertions, 63 deletions

diff --git a/tests/README.md b/tests/README.md
index be78821bf..4f62edd68 100644
--- a/tests/README.md
+++ b/tests/README.md
@@ -83,7 +83,7 @@ TagContentConverter should return correct values for valid input.
 As we are trying to test our "units" of code independently, we want to make sure that we do not rely objects and data generated by "external" code. If we we did, then we wouldn't know if the failure we're observing was caused by the code we are actually trying to test or something external to it.
 
 
-However, the features that we are trying to test often depend on those objects generated by external pieces of code. It would be difficult to test a bot command without having access to a `Context` instance. Fortunately, there's a solution for that: we use fake objects that act like the true object. We call these fake objects "mocks". 
+However, the features that we are trying to test often depend on those objects generated by external pieces of code. It would be difficult to test a bot command without having access to a `Context` instance. Fortunately, there's a solution for that: we use fake objects that act like the true object. We call these fake objects "mocks".
 
 To create these mock object, we mainly use the [`unittest.mock`](https://docs.python.org/3/library/unittest.mock.html) module. In addition, we have also defined a couple of specialized mock objects that mock specific `discord.py` types (see the section on the below.).
 
@@ -114,13 +114,13 @@ class BotCogTests(unittest.TestCase):
 
 ### Mocking coroutines
 
-By default, the `unittest.mock.Mock` and `unittest.mock.MagicMock` classes cannot mock coroutines, since the `__call__` method they provide is synchronous. In anticipation of the `AsyncMock` that will be [introduced in Python 3.8](https://docs.python.org/3.9/whatsnew/3.8.html#unittest), we have added an `AsyncMock` helper to [`helpers.py`](/tests/helpers.py). Do note that this drop-in replacement only implements an asynchronous `__call__` method, not the additional assertions that will come with the new `AsyncMock` type in Python 3.8. 
+By default, the `unittest.mock.Mock` and `unittest.mock.MagicMock` classes cannot mock coroutines, since the `__call__` method they provide is synchronous. In anticipation of the `AsyncMock` that will be [introduced in Python 3.8](https://docs.python.org/3.9/whatsnew/3.8.html#unittest), we have added an `AsyncMock` helper to [`helpers.py`](/tests/helpers.py). Do note that this drop-in replacement only implements an asynchronous `__call__` method, not the additional assertions that will come with the new `AsyncMock` type in Python 3.8.
 
 ### Special mocks for some `discord.py` types
 
 To quote Ned Batchelder, Mock objects are "automatic chameleons". This means that they will happily allow the access to any attribute or method and provide a mocked value in return. One downside to this is that if the code you are testing gets the name of the attribute wrong, your mock object will not complain and the test may still pass.
 
-In order to avoid that, we have defined a number of Mock types in [`helpers.py`](/tests/helpers.py) that follow the specifications of the actual Discord types they are mocking. This means that trying to access an attribute or method on a mocked object that does not exist on the equivalent `discord.py` object will result in an `AttributeError`. In addition, these mocks have some sensible defaults and **pass `isinstance` checks for the types they are mocking**. 
+In order to avoid that, we have defined a number of Mock types in [`helpers.py`](/tests/helpers.py) that follow the specifications of the actual Discord types they are mocking. This means that trying to access an attribute or method on a mocked object that does not exist on the equivalent `discord.py` object will result in an `AttributeError`. In addition, these mocks have some sensible defaults and **pass `isinstance` checks for the types they are mocking**.
 
 These special mocks are added when they are needed, so if you think it would be sensible to add another one, feel free to propose one in your PR.
 
@@ -144,7 +144,7 @@ Finally, there are some considerations to make when writing tests, both for writ
 
 ### Test coverage is a starting point
 
-Having test coverage is a good starting point for unit testing: If a part of your code was not covered by a test, we know that we have not tested it properly. The reverse is unfortunately not true: Even if the code we are testing has 100% branch coverage, it does not mean it's fully tested or guaranteed to work. 
+Having test coverage is a good starting point for unit testing: If a part of your code was not covered by a test, we know that we have not tested it properly. The reverse is unfortunately not true: Even if the code we are testing has 100% branch coverage, it does not mean it's fully tested or guaranteed to work.
 
 One problem is that 100% branch coverage may be misleading if we haven't tested our code against all the realistic input it may get in production. For instance, take a look at the following `member_information` function and the test we've written for it:
 
@@ -169,7 +169,7 @@ class FunctionsTests(unittest.TestCase):
 
 If you were to run this test, not only would the function pass the test, `coverage.py` will also tell us that the test provides 100% branch coverage for the function. Can you spot the bug the test suite did not catch?
 
-The problem here is that we have only tested our function with a member object that had `None` for the `member.joined` attribute. This means that `member.joined.stfptime("%d-%m-%Y")` was never executed during our test, leading to us missing the spelling mistake in `stfptime` (it should be `strftime`). 
+The problem here is that we have only tested our function with a member object that had `None` for the `member.joined` attribute. This means that `member.joined.stfptime("%d-%m-%Y")` was never executed during our test, leading to us missing the spelling mistake in `stfptime` (it should be `strftime`).
 
 Adding another test would not increase the test coverage we have, but it does ensure that we'll notice that this function can fail with realistic data:
 
diff --git a/tests/base.py b/tests/base.py
index 42174e911..d99b9ac31 100644
--- a/tests/base.py
+++ b/tests/base.py
@@ -31,7 +31,7 @@ class LoggingTestsMixin:
     """
 
     @contextmanager
-    def assertNotLogs(self, logger=None, level=None, msg=None):
+    def assertNotLogs(self, logger=None, level=None, msg=None):  # noqa: N802
         """
         Asserts that no logs of `level` and higher were emitted by `logger`.
 
@@ -81,7 +81,7 @@ class LoggingTestsMixin:
 class CommandTestCase(unittest.IsolatedAsyncioTestCase):
     """TestCase with additional assertions that are useful for testing Discord commands."""
 
-    async def assertHasPermissionsCheck(
+    async def assertHasPermissionsCheck(  # noqa: N802
         self,
         cmd: commands.Command,
         permissions: Dict[str, bool],
diff --git a/tests/bot/cogs/moderation/test_silence.py b/tests/bot/cogs/moderation/test_silence.py
new file mode 100644
index 000000000..3fd149f04
--- /dev/null
+++ b/tests/bot/cogs/moderation/test_silence.py
@@ -0,0 +1,251 @@
+import unittest
+from unittest import mock
+from unittest.mock import MagicMock, Mock
+
+from discord import PermissionOverwrite
+
+from bot.cogs.moderation.silence import Silence, SilenceNotifier
+from bot.constants import Channels, Emojis, Guild, Roles
+from tests.helpers import MockBot, MockContext, MockTextChannel
+
+
+class SilenceNotifierTests(unittest.IsolatedAsyncioTestCase):
+    def setUp(self) -> None:
+        self.alert_channel = MockTextChannel()
+        self.notifier = SilenceNotifier(self.alert_channel)
+        self.notifier.stop = self.notifier_stop_mock = Mock()
+        self.notifier.start = self.notifier_start_mock = Mock()
+
+    def test_add_channel_adds_channel(self):
+        """Channel in FirstHash with current loop is added to internal set."""
+        channel = Mock()
+        with mock.patch.object(self.notifier, "_silenced_channels") as silenced_channels:
+            self.notifier.add_channel(channel)
+        silenced_channels.__setitem__.assert_called_with(channel, self.notifier._current_loop)
+
+    def test_add_channel_starts_loop(self):
+        """Loop is started if `_silenced_channels` was empty."""
+        self.notifier.add_channel(Mock())
+        self.notifier_start_mock.assert_called_once()
+
+    def test_add_channel_skips_start_with_channels(self):
+        """Loop start is not called when `_silenced_channels` is not empty."""
+        with mock.patch.object(self.notifier, "_silenced_channels"):
+            self.notifier.add_channel(Mock())
+        self.notifier_start_mock.assert_not_called()
+
+    def test_remove_channel_removes_channel(self):
+        """Channel in FirstHash is removed from `_silenced_channels`."""
+        channel = Mock()
+        with mock.patch.object(self.notifier, "_silenced_channels") as silenced_channels:
+            self.notifier.remove_channel(channel)
+        silenced_channels.__delitem__.assert_called_with(channel)
+
+    def test_remove_channel_stops_loop(self):
+        """Notifier loop is stopped if `_silenced_channels` is empty after remove."""
+        with mock.patch.object(self.notifier, "_silenced_channels", __bool__=lambda _: False):
+            self.notifier.remove_channel(Mock())
+        self.notifier_stop_mock.assert_called_once()
+
+    def test_remove_channel_skips_stop_with_channels(self):
+        """Notifier loop is not stopped if `_silenced_channels` is not empty after remove."""
+        self.notifier.remove_channel(Mock())
+        self.notifier_stop_mock.assert_not_called()
+
+    async def test_notifier_private_sends_alert(self):
+        """Alert is sent on 15 min intervals."""
+        test_cases = (900, 1800, 2700)
+        for current_loop in test_cases:
+            with self.subTest(current_loop=current_loop):
+                with mock.patch.object(self.notifier, "_current_loop", new=current_loop):
+                    await self.notifier._notifier()
+                self.alert_channel.send.assert_called_once_with(f"<@&{Roles.moderators}> currently silenced channels: ")
+            self.alert_channel.send.reset_mock()
+
+    async def test_notifier_skips_alert(self):
+        """Alert is skipped on first loop or not an increment of 900."""
+        test_cases = (0, 15, 5000)
+        for current_loop in test_cases:
+            with self.subTest(current_loop=current_loop):
+                with mock.patch.object(self.notifier, "_current_loop", new=current_loop):
+                    await self.notifier._notifier()
+                    self.alert_channel.send.assert_not_called()
+
+
+class SilenceTests(unittest.IsolatedAsyncioTestCase):
+    def setUp(self) -> None:
+        self.bot = MockBot()
+        self.cog = Silence(self.bot)
+        self.ctx = MockContext()
+        self.cog._verified_role = None
+        # Set event so command callbacks can continue.
+        self.cog._get_instance_vars_event.set()
+
+    async def test_instance_vars_got_guild(self):
+        """Bot got guild after it became available."""
+        await self.cog._get_instance_vars()
+        self.bot.wait_until_guild_available.assert_called_once()
+        self.bot.get_guild.assert_called_once_with(Guild.id)
+
+    async def test_instance_vars_got_role(self):
+        """Got `Roles.verified` role from guild."""
+        await self.cog._get_instance_vars()
+        guild = self.bot.get_guild()
+        guild.get_role.assert_called_once_with(Roles.verified)
+
+    async def test_instance_vars_got_channels(self):
+        """Got channels from bot."""
+        await self.cog._get_instance_vars()
+        self.bot.get_channel.called_once_with(Channels.mod_alerts)
+        self.bot.get_channel.called_once_with(Channels.mod_log)
+
+    @mock.patch("bot.cogs.moderation.silence.SilenceNotifier")
+    async def test_instance_vars_got_notifier(self, notifier):
+        """Notifier was started with channel."""
+        mod_log = MockTextChannel()
+        self.bot.get_channel.side_effect = (None, mod_log)
+        await self.cog._get_instance_vars()
+        notifier.assert_called_once_with(mod_log)
+        self.bot.get_channel.side_effect = None
+
+    async def test_silence_sent_correct_discord_message(self):
+        """Check if proper message was sent when called with duration in channel with previous state."""
+        test_cases = (
+            (0.0001, f"{Emojis.check_mark} silenced current channel for 0.0001 minute(s).", True,),
+            (None, f"{Emojis.check_mark} silenced current channel indefinitely.", True,),
+            (5, f"{Emojis.cross_mark} current channel is already silenced.", False,),
+        )
+        for duration, result_message, _silence_patch_return in test_cases:
+            with self.subTest(
+                silence_duration=duration,
+                result_message=result_message,
+                starting_unsilenced_state=_silence_patch_return
+            ):
+                with mock.patch.object(self.cog, "_silence", return_value=_silence_patch_return):
+                    await self.cog.silence.callback(self.cog, self.ctx, duration)
+                    self.ctx.send.assert_called_once_with(result_message)
+            self.ctx.reset_mock()
+
+    async def test_unsilence_sent_correct_discord_message(self):
+        """Proper reply after a successful unsilence."""
+        with mock.patch.object(self.cog, "_unsilence", return_value=True):
+            await self.cog.unsilence.callback(self.cog, self.ctx)
+            self.ctx.send.assert_called_once_with(f"{Emojis.check_mark} unsilenced current channel.")
+
+    async def test_silence_private_for_false(self):
+        """Permissions are not set and `False` is returned in an already silenced channel."""
+        perm_overwrite = Mock(send_messages=False)
+        channel = Mock(overwrites_for=Mock(return_value=perm_overwrite))
+
+        self.assertFalse(await self.cog._silence(channel, True, None))
+        channel.set_permissions.assert_not_called()
+
+    async def test_silence_private_silenced_channel(self):
+        """Channel had `send_message` permissions revoked."""
+        channel = MockTextChannel()
+        self.assertTrue(await self.cog._silence(channel, False, None))
+        channel.set_permissions.assert_called_once()
+        self.assertFalse(channel.set_permissions.call_args.kwargs['send_messages'])
+
+    async def test_silence_private_preserves_permissions(self):
+        """Previous permissions were preserved when channel was silenced."""
+        channel = MockTextChannel()
+        # Set up mock channel permission state.
+        mock_permissions = PermissionOverwrite()
+        mock_permissions_dict = dict(mock_permissions)
+        channel.overwrites_for.return_value = mock_permissions
+        await self.cog._silence(channel, False, None)
+        new_permissions = channel.set_permissions.call_args.kwargs
+        # Remove 'send_messages' key because it got changed in the method.
+        del new_permissions['send_messages']
+        del mock_permissions_dict['send_messages']
+        self.assertDictEqual(mock_permissions_dict, new_permissions)
+
+    async def test_silence_private_notifier(self):
+        """Channel should be added to notifier with `persistent` set to `True`, and the other way around."""
+        channel = MockTextChannel()
+        with mock.patch.object(self.cog, "notifier", create=True):
+            with self.subTest(persistent=True):
+                await self.cog._silence(channel, True, None)
+                self.cog.notifier.add_channel.assert_called_once()
+
+        with mock.patch.object(self.cog, "notifier", create=True):
+            with self.subTest(persistent=False):
+                await self.cog._silence(channel, False, None)
+                self.cog.notifier.add_channel.assert_not_called()
+
+    async def test_silence_private_added_muted_channel(self):
+        """Channel was added to `muted_channels` on silence."""
+        channel = MockTextChannel()
+        with mock.patch.object(self.cog, "muted_channels") as muted_channels:
+            await self.cog._silence(channel, False, None)
+        muted_channels.add.assert_called_once_with(channel)
+
+    async def test_unsilence_private_for_false(self):
+        """Permissions are not set and `False` is returned in an unsilenced channel."""
+        channel = Mock()
+        self.assertFalse(await self.cog._unsilence(channel))
+        channel.set_permissions.assert_not_called()
+
+    @mock.patch.object(Silence, "notifier", create=True)
+    async def test_unsilence_private_unsilenced_channel(self, _):
+        """Channel had `send_message` permissions restored"""
+        perm_overwrite = MagicMock(send_messages=False)
+        channel = MockTextChannel(overwrites_for=Mock(return_value=perm_overwrite))
+        self.assertTrue(await self.cog._unsilence(channel))
+        channel.set_permissions.assert_called_once()
+        self.assertIsNone(channel.set_permissions.call_args.kwargs['send_messages'])
+
+    @mock.patch.object(Silence, "notifier", create=True)
+    async def test_unsilence_private_removed_notifier(self, notifier):
+        """Channel was removed from `notifier` on unsilence."""
+        perm_overwrite = MagicMock(send_messages=False)
+        channel = MockTextChannel(overwrites_for=Mock(return_value=perm_overwrite))
+        await self.cog._unsilence(channel)
+        notifier.remove_channel.assert_called_once_with(channel)
+
+    @mock.patch.object(Silence, "notifier", create=True)
+    async def test_unsilence_private_removed_muted_channel(self, _):
+        """Channel was removed from `muted_channels` on unsilence."""
+        perm_overwrite = MagicMock(send_messages=False)
+        channel = MockTextChannel(overwrites_for=Mock(return_value=perm_overwrite))
+        with mock.patch.object(self.cog, "muted_channels") as muted_channels:
+            await self.cog._unsilence(channel)
+        muted_channels.discard.assert_called_once_with(channel)
+
+    @mock.patch.object(Silence, "notifier", create=True)
+    async def test_unsilence_private_preserves_permissions(self, _):
+        """Previous permissions were preserved when channel was unsilenced."""
+        channel = MockTextChannel()
+        # Set up mock channel permission state.
+        mock_permissions = PermissionOverwrite(send_messages=False)
+        mock_permissions_dict = dict(mock_permissions)
+        channel.overwrites_for.return_value = mock_permissions
+        await self.cog._unsilence(channel)
+        new_permissions = channel.set_permissions.call_args.kwargs
+        # Remove 'send_messages' key because it got changed in the method.
+        del new_permissions['send_messages']
+        del mock_permissions_dict['send_messages']
+        self.assertDictEqual(mock_permissions_dict, new_permissions)
+
+    @mock.patch("bot.cogs.moderation.silence.asyncio")
+    @mock.patch.object(Silence, "_mod_alerts_channel", create=True)
+    def test_cog_unload_starts_task(self, alert_channel, asyncio_mock):
+        """Task for sending an alert was created with present `muted_channels`."""
+        with mock.patch.object(self.cog, "muted_channels"):
+            self.cog.cog_unload()
+            alert_channel.send.assert_called_once_with(f"<@&{Roles.moderators}> channels left silenced on cog unload: ")
+            asyncio_mock.create_task.assert_called_once_with(alert_channel.send())
+
+    @mock.patch("bot.cogs.moderation.silence.asyncio")
+    def test_cog_unload_skips_task_start(self, asyncio_mock):
+        """No task created with no channels."""
+        self.cog.cog_unload()
+        asyncio_mock.create_task.assert_not_called()
+
+    @mock.patch("bot.cogs.moderation.silence.with_role_check")
+    @mock.patch("bot.cogs.moderation.silence.MODERATION_ROLES", new=(1, 2, 3))
+    def test_cog_check(self, role_check):
+        """Role check is called with `MODERATION_ROLES`"""
+        self.cog.cog_check(self.ctx)
+        role_check.assert_called_once_with(self.ctx, *(1, 2, 3))
diff --git a/tests/bot/cogs/sync/test_base.py b/tests/bot/cogs/sync/test_base.py
index fe0594efe..70aea2bab 100644
--- a/tests/bot/cogs/sync/test_base.py
+++ b/tests/bot/cogs/sync/test_base.py
@@ -1,3 +1,4 @@
+import asyncio
 import unittest
 from unittest import mock
 
@@ -84,7 +85,7 @@ class SyncerSendPromptTests(unittest.IsolatedAsyncioTestCase):
 
                 method.assert_called_once_with(constants.Channels.dev_core)
 
-    async def test_send_prompt_returns_None_if_channel_fetch_fails(self):
+    async def test_send_prompt_returns_none_if_channel_fetch_fails(self):
         """None should be returned if there's an HTTPException when fetching the channel."""
         self.bot.get_channel.return_value = None
         self.bot.fetch_channel.side_effect = discord.HTTPException(mock.MagicMock(), "test error!")
@@ -211,7 +212,7 @@ class SyncerConfirmationTests(unittest.IsolatedAsyncioTestCase):
         subtests = (
             (constants.Emojis.check_mark, True, None),
             ("InVaLiD", False, None),
-            (None, False, TimeoutError),
+            (None, False, asyncio.TimeoutError),
         )
 
         for emoji, ret_val, side_effect in subtests:
diff --git a/tests/bot/cogs/test_cogs.py b/tests/bot/cogs/test_cogs.py
new file mode 100644
index 000000000..fdda59a8f
--- /dev/null
+++ b/tests/bot/cogs/test_cogs.py
@@ -0,0 +1,80 @@
+"""Test suite for general tests which apply to all cogs."""
+
+import importlib
+import pkgutil
+import typing as t
+import unittest
+from collections import defaultdict
+from types import ModuleType
+from unittest import mock
+
+from discord.ext import commands
+
+from bot import cogs
+
+
+class CommandNameTests(unittest.TestCase):
+    """Tests for shadowing command names and aliases."""
+
+    @staticmethod
+    def walk_commands(cog: commands.Cog) -> t.Iterator[commands.Command]:
+        """An iterator that recursively walks through `cog`'s commands and subcommands."""
+        # Can't use Bot.walk_commands() or Cog.get_commands() cause those are instance methods.
+        for command in cog.__cog_commands__:
+            if command.parent is None:
+                yield command
+                if isinstance(command, commands.GroupMixin):
+                    # Annoyingly it returns duplicates for each alias so use a set to fix that
+                    yield from set(command.walk_commands())
+
+    @staticmethod
+    def walk_modules() -> t.Iterator[ModuleType]:
+        """Yield imported modules from the bot.cogs subpackage."""
+        def on_error(name: str) -> t.NoReturn:
+            raise ImportError(name=name)  # pragma: no cover
+
+        # The mock prevents asyncio.get_event_loop() from being called.
+        with mock.patch("discord.ext.tasks.loop"):
+            for module in pkgutil.walk_packages(cogs.__path__, "bot.cogs.", onerror=on_error):
+                if not module.ispkg:
+                    yield importlib.import_module(module.name)
+
+    @staticmethod
+    def walk_cogs(module: ModuleType) -> t.Iterator[commands.Cog]:
+        """Yield all cogs defined in an extension."""
+        for obj in module.__dict__.values():
+            # Check if it's a class type cause otherwise issubclass() may raise a TypeError.
+            is_cog = isinstance(obj, type) and issubclass(obj, commands.Cog)
+            if is_cog and obj.__module__ == module.__name__:
+                yield obj
+
+    @staticmethod
+    def get_qualified_names(command: commands.Command) -> t.List[str]:
+        """Return a list of all qualified names, including aliases, for the `command`."""
+        names = [f"{command.full_parent_name} {alias}".strip() for alias in command.aliases]
+        names.append(command.qualified_name)
+
+        return names
+
+    def get_all_commands(self) -> t.Iterator[commands.Command]:
+        """Yield all commands for all cogs in all extensions."""
+        for module in self.walk_modules():
+            for cog in self.walk_cogs(module):
+                for cmd in self.walk_commands(cog):
+                    yield cmd
+
+    def test_names_dont_shadow(self):
+        """Names and aliases of commands should be unique."""
+        all_names = defaultdict(list)
+        for cmd in self.get_all_commands():
+            func_name = f"{cmd.module}.{cmd.callback.__qualname__}"
+
+            for name in self.get_qualified_names(cmd):
+                with self.subTest(cmd=func_name, name=name):
+                    if name in all_names:  # pragma: no cover
+                        conflicts = ", ".join(all_names.get(name, ""))
+                        self.fail(
+                            f"Name '{name}' of the command {func_name} conflicts with {conflicts}."
+                        )
+
+                all_names[name].append(func_name)
diff --git a/tests/bot/cogs/test_information.py b/tests/bot/cogs/test_information.py
index 5693d2946..b5f928dd6 100644
--- a/tests/bot/cogs/test_information.py
+++ b/tests/bot/cogs/test_information.py
@@ -7,7 +7,7 @@ import discord
 
 from bot import constants
 from bot.cogs import information
-from bot.decorators import InChannelCheckFailure
+from bot.decorators import InWhitelistCheckFailure
 from tests import helpers
 
 
@@ -45,10 +45,9 @@ class InformationCogTests(unittest.TestCase):
         _, kwargs = self.ctx.send.call_args
         embed = kwargs.pop('embed')
 
-        self.assertEqual(embed.title, "Role information")
+        self.assertEqual(embed.title, "Role information (Total 1 role)")
         self.assertEqual(embed.colour, discord.Colour.blurple())
-        self.assertEqual(embed.description, f"`{self.moderator_role.id}` - {self.moderator_role.mention}\n")
-        self.assertEqual(embed.footer.text, "Total roles: 1")
+        self.assertEqual(embed.description, f"\n`{self.moderator_role.id}` - {self.moderator_role.mention}\n")
 
     def test_role_info_command(self):
         """Tests the `role info` command."""
@@ -486,7 +485,7 @@ class UserEmbedTests(unittest.TestCase):
         user.avatar_url_as.return_value = "avatar url"
         embed = asyncio.run(self.cog.create_user_embed(ctx, user))
 
-        user.avatar_url_as.assert_called_once_with(format="png")
+        user.avatar_url_as.assert_called_once_with(static_format="png")
         self.assertEqual(embed.thumbnail.url, "avatar url")
 
 
@@ -526,7 +525,7 @@ class UserCommandTests(unittest.TestCase):
         ctx = helpers.MockContext(author=self.author, channel=helpers.MockTextChannel(id=100))
 
         msg = "Sorry, but you may only use this command within <#50>."
-        with self.assertRaises(InChannelCheckFailure, msg=msg):
+        with self.assertRaises(InWhitelistCheckFailure, msg=msg):
             asyncio.run(self.cog.user_info.callback(self.cog, ctx))
 
     @unittest.mock.patch("bot.cogs.information.Information.create_user_embed", new_callable=unittest.mock.AsyncMock)
diff --git a/tests/bot/cogs/test_snekbox.py b/tests/bot/cogs/test_snekbox.py
index 9cd7f0154..1dec0ccaf 100644
--- a/tests/bot/cogs/test_snekbox.py
+++ b/tests/bot/cogs/test_snekbox.py
@@ -1,11 +1,13 @@
 import asyncio
 import logging
 import unittest
-from unittest.mock import AsyncMock, MagicMock, Mock, call, patch
+from unittest.mock import AsyncMock, MagicMock, Mock, call, create_autospec, patch
 
+from discord.ext import commands
+
+from bot import constants
 from bot.cogs import snekbox
 from bot.cogs.snekbox import Snekbox
-from bot.constants import URLs
 from tests.helpers import MockBot, MockContext, MockMessage, MockReaction, MockUser
 
 
@@ -23,7 +25,7 @@ class SnekboxTests(unittest.IsolatedAsyncioTestCase):
 
         self.assertEqual(await self.cog.post_eval("import random"), "return")
         self.bot.http_session.post.assert_called_with(
-            URLs.snekbox_eval_api,
+            constants.URLs.snekbox_eval_api,
             json={"input": "import random"},
             raise_for_status=True
         )
@@ -43,10 +45,10 @@ class SnekboxTests(unittest.IsolatedAsyncioTestCase):
 
         self.assertEqual(
             await self.cog.upload_output("My awesome output"),
-            URLs.paste_service.format(key=key)
+            constants.URLs.paste_service.format(key=key)
         )
         self.bot.http_session.post.assert_called_with(
-            URLs.paste_service.format(key="documents"),
+            constants.URLs.paste_service.format(key="documents"),
             data="My awesome output",
             raise_for_status=True
         )
@@ -89,15 +91,15 @@ class SnekboxTests(unittest.IsolatedAsyncioTestCase):
                 self.assertEqual(actual, expected)
 
     @patch('bot.cogs.snekbox.Signals', side_effect=ValueError)
-    def test_get_results_message_invalid_signal(self, mock_Signals: Mock):
+    def test_get_results_message_invalid_signal(self, mock_signals: Mock):
         self.assertEqual(
             self.cog.get_results_message({'stdout': '', 'returncode': 127}),
             ('Your eval job has completed with return code 127', '')
         )
 
     @patch('bot.cogs.snekbox.Signals')
-    def test_get_results_message_valid_signal(self, mock_Signals: Mock):
-        mock_Signals.return_value.name = 'SIGTEST'
+    def test_get_results_message_valid_signal(self, mock_signals: Mock):
+        mock_signals.return_value.name = 'SIGTEST'
         self.assertEqual(
             self.cog.get_results_message({'stdout': '', 'returncode': 127}),
             ('Your eval job has completed with return code 127 (SIGTEST)', '')
@@ -279,11 +281,14 @@ class SnekboxTests(unittest.IsolatedAsyncioTestCase):
         """Test that the continue_eval function does continue if required conditions are met."""
         ctx = MockContext(message=MockMessage(add_reaction=AsyncMock(), clear_reactions=AsyncMock()))
         response = MockMessage(delete=AsyncMock())
-        new_msg = MockMessage(content='!e NewCode')
+        new_msg = MockMessage()
         self.bot.wait_for.side_effect = ((None, new_msg), None)
+        expected = "NewCode"
+        self.cog.get_code = create_autospec(self.cog.get_code, spec_set=True, return_value=expected)
 
         actual = await self.cog.continue_eval(ctx, response)
-        self.assertEqual(actual, 'NewCode')
+        self.cog.get_code.assert_awaited_once_with(new_msg)
+        self.assertEqual(actual, expected)
         self.bot.wait_for.assert_has_awaits(
             (
                 call('message_edit', check=partial_mock(snekbox.predicate_eval_message_edit, ctx), timeout=10),
@@ -302,6 +307,32 @@ class SnekboxTests(unittest.IsolatedAsyncioTestCase):
         self.assertEqual(actual, None)
         ctx.message.clear_reactions.assert_called_once()
 
+    async def test_get_code(self):
+        """Should return 1st arg (or None) if eval cmd in message, otherwise return full content."""
+        prefix = constants.Bot.prefix
+        subtests = (
+            (self.cog.eval_command, f"{prefix}{self.cog.eval_command.name} print(1)", "print(1)"),
+            (self.cog.eval_command, f"{prefix}{self.cog.eval_command.name}", None),
+            (MagicMock(spec=commands.Command), f"{prefix}tags get foo"),
+            (None, "print(123)")
+        )
+
+        for command, content, *expected_code in subtests:
+            if not expected_code:
+                expected_code = content
+            else:
+                [expected_code] = expected_code
+
+            with self.subTest(content=content, expected_code=expected_code):
+                self.bot.get_context.reset_mock()
+                self.bot.get_context.return_value = MockContext(command=command)
+                message = MockMessage(content=content)
+
+                actual_code = await self.cog.get_code(message)
+
+                self.bot.get_context.assert_awaited_once_with(message)
+                self.assertEqual(actual_code, expected_code)
+
     def test_predicate_eval_message_edit(self):
         """Test the predicate_eval_message_edit function."""
         msg0 = MockMessage(id=1, content='abc')
diff --git a/tests/bot/test_converters.py b/tests/bot/test_converters.py
index 1e5ca62ae..ca8cb6825 100644
--- a/tests/bot/test_converters.py
+++ b/tests/bot/test_converters.py
@@ -8,6 +8,7 @@ from discord.ext.commands import BadArgument
 
 from bot.converters import (
     Duration,
+    HushDurationConverter,
     ISODateTime,
     TagContentConverter,
     TagNameConverter,
@@ -271,3 +272,32 @@ class ConverterTests(unittest.TestCase):
                 exception_message = f"`{datetime_string}` is not a valid ISO-8601 datetime string"
                 with self.assertRaises(BadArgument, msg=exception_message):
                     asyncio.run(converter.convert(self.context, datetime_string))
+
+    def test_hush_duration_converter_for_valid(self):
+        """HushDurationConverter returns correct value for minutes duration or `"forever"` strings."""
+        test_values = (
+            ("0", 0),
+            ("15", 15),
+            ("10", 10),
+            ("5m", 5),
+            ("5M", 5),
+            ("forever", None),
+        )
+        converter = HushDurationConverter()
+        for minutes_string, expected_minutes in test_values:
+            with self.subTest(minutes_string=minutes_string, expected_minutes=expected_minutes):
+                converted = asyncio.run(converter.convert(self.context, minutes_string))
+                self.assertEqual(expected_minutes, converted)
+
+    def test_hush_duration_converter_for_invalid(self):
+        """HushDurationConverter raises correct exception for invalid minutes duration strings."""
+        test_values = (
+            ("16", "Duration must be at most 15 minutes."),
+            ("10d", "10d is not a valid minutes duration."),
+            ("-1", "-1 is not a valid minutes duration."),
+        )
+        converter = HushDurationConverter()
+        for invalid_minutes_string, exception_message in test_values:
+            with self.subTest(invalid_minutes_string=invalid_minutes_string, exception_message=exception_message):
+                with self.assertRaisesRegex(BadArgument, exception_message):
+                    asyncio.run(converter.convert(self.context, invalid_minutes_string))
diff --git a/tests/bot/test_decorators.py b/tests/bot/test_decorators.py
new file mode 100644
index 000000000..a17dd3e16
--- /dev/null
+++ b/tests/bot/test_decorators.py
@@ -0,0 +1,147 @@
+import collections
+import unittest
+import unittest.mock
+
+from bot import constants
+from bot.decorators import InWhitelistCheckFailure, in_whitelist
+from tests import helpers
+
+
+InWhitelistTestCase = collections.namedtuple("WhitelistedContextTestCase", ("kwargs", "ctx", "description"))
+
+
+class InWhitelistTests(unittest.TestCase):
+    """Tests for the `in_whitelist` check."""
+
+    @classmethod
+    def setUpClass(cls):
+        """Set up helpers that only need to be defined once."""
+        cls.bot_commands = helpers.MockTextChannel(id=123456789, category_id=123456)
+        cls.help_channel = helpers.MockTextChannel(id=987654321, category_id=987654)
+        cls.non_whitelisted_channel = helpers.MockTextChannel(id=666666)
+        cls.dm_channel = helpers.MockDMChannel()
+
+        cls.non_staff_member = helpers.MockMember()
+        cls.staff_role = helpers.MockRole(id=121212)
+        cls.staff_member = helpers.MockMember(roles=(cls.staff_role,))
+
+        cls.channels = (cls.bot_commands.id,)
+        cls.categories = (cls.help_channel.category_id,)
+        cls.roles = (cls.staff_role.id,)
+
+    def test_predicate_returns_true_for_whitelisted_context(self):
+        """The predicate should return `True` if a whitelisted context was passed to it."""
+        test_cases = (
+            InWhitelistTestCase(
+                kwargs={"channels": self.channels},
+                ctx=helpers.MockContext(channel=self.bot_commands, author=self.non_staff_member),
+                description="In whitelisted channels by members without whitelisted roles",
+            ),
+            InWhitelistTestCase(
+                kwargs={"redirect": self.bot_commands.id},
+                ctx=helpers.MockContext(channel=self.bot_commands, author=self.non_staff_member),
+                description="`redirect` should be implicitly added to `channels`",
+            ),
+            InWhitelistTestCase(
+                kwargs={"categories": self.categories},
+                ctx=helpers.MockContext(channel=self.help_channel, author=self.non_staff_member),
+                description="Whitelisted category without whitelisted role",
+            ),
+            InWhitelistTestCase(
+                kwargs={"roles": self.roles},
+                ctx=helpers.MockContext(channel=self.non_whitelisted_channel, author=self.staff_member),
+                description="Whitelisted role outside of whitelisted channel/category"
+            ),
+            InWhitelistTestCase(
+                kwargs={
+                    "channels": self.channels,
+                    "categories": self.categories,
+                    "roles": self.roles,
+                    "redirect": self.bot_commands,
+                },
+                ctx=helpers.MockContext(channel=self.help_channel, author=self.staff_member),
+                description="Case with all whitelist kwargs used",
+            ),
+        )
+
+        for test_case in test_cases:
+            # patch `commands.check` with a no-op lambda that just returns the predicate passed to it
+            # so we can test the predicate that was generated from the specified kwargs.
+            with unittest.mock.patch("bot.decorators.commands.check", new=lambda predicate: predicate):
+                predicate = in_whitelist(**test_case.kwargs)
+
+            with self.subTest(test_description=test_case.description):
+                self.assertTrue(predicate(test_case.ctx))
+
+    def test_predicate_raises_exception_for_non_whitelisted_context(self):
+        """The predicate should raise `InWhitelistCheckFailure` for a non-whitelisted context."""
+        test_cases = (
+            # Failing check with explicit `redirect`
+            InWhitelistTestCase(
+                kwargs={
+                    "categories": self.categories,
+                    "channels": self.channels,
+                    "roles": self.roles,
+                    "redirect": self.bot_commands.id,
+                },
+                ctx=helpers.MockContext(channel=self.non_whitelisted_channel, author=self.non_staff_member),
+                description="Failing check with an explicit redirect channel",
+            ),
+
+            # Failing check with implicit `redirect`
+            InWhitelistTestCase(
+                kwargs={
+                    "categories": self.categories,
+                    "channels": self.channels,
+                    "roles": self.roles,
+                },
+                ctx=helpers.MockContext(channel=self.non_whitelisted_channel, author=self.non_staff_member),
+                description="Failing check with an implicit redirect channel",
+            ),
+
+            # Failing check without `redirect`
+            InWhitelistTestCase(
+                kwargs={
+                    "categories": self.categories,
+                    "channels": self.channels,
+                    "roles": self.roles,
+                    "redirect": None,
+                },
+                ctx=helpers.MockContext(channel=self.non_whitelisted_channel, author=self.non_staff_member),
+                description="Failing check without a redirect channel",
+            ),
+
+            # Command issued in DM channel
+            InWhitelistTestCase(
+                kwargs={
+                    "categories": self.categories,
+                    "channels": self.channels,
+                    "roles": self.roles,
+                    "redirect": None,
+                },
+                ctx=helpers.MockContext(channel=self.dm_channel, author=self.dm_channel.me),
+                description="Commands issued in DM channel should be rejected",
+            ),
+        )
+
+        for test_case in test_cases:
+            if "redirect" not in test_case.kwargs or test_case.kwargs["redirect"] is not None:
+                # There are two cases in which we have a redirect channel:
+                #   1. No redirect channel was passed; the default value of `bot_commands` is used
+                #   2. An explicit `redirect` is set that is "not None"
+                redirect_channel = test_case.kwargs.get("redirect", constants.Channels.bot_commands)
+                redirect_message = f" here. Please use the <#{redirect_channel}> channel instead"
+            else:
+                # If an explicit `None` was passed for `redirect`, there is no redirect channel
+                redirect_message = ""
+
+            exception_message = f"You are not allowed to use that command{redirect_message}."
+
+            # patch `commands.check` with a no-op lambda that just returns the predicate passed to it
+            # so we can test the predicate that was generated from the specified kwargs.
+            with unittest.mock.patch("bot.decorators.commands.check", new=lambda predicate: predicate):
+                predicate = in_whitelist(**test_case.kwargs)
+
+            with self.subTest(test_description=test_case.description):
+                with self.assertRaisesRegex(InWhitelistCheckFailure, exception_message):
+                    predicate(test_case.ctx)
diff --git a/tests/bot/test_utils.py b/tests/bot/test_utils.py
deleted file mode 100644
index d7bcc3ba6..000000000
--- a/tests/bot/test_utils.py
+++ /dev/null
@@ -1,37 +0,0 @@
-import unittest
-
-from bot import utils
-
-
-class CaseInsensitiveDictTests(unittest.TestCase):
-    """Tests for the `CaseInsensitiveDict` container."""
-
-    def test_case_insensitive_key_access(self):
-        """Tests case insensitive key access and storage."""
-        instance = utils.CaseInsensitiveDict()
-
-        key = 'LEMON'
-        value = 'trees'
-
-        instance[key] = value
-        self.assertIn(key, instance)
-        self.assertEqual(instance.get(key), value)
-        self.assertEqual(instance.get(key.casefold()), value)
-        self.assertEqual(instance.pop(key.casefold()), value)
-        self.assertNotIn(key, instance)
-        self.assertNotIn(key.casefold(), instance)
-
-        instance.setdefault(key, value)
-        del instance[key]
-        self.assertNotIn(key, instance)
-
-    def test_initialization_from_kwargs(self):
-        """Tests creating the dictionary from keyword arguments."""
-        instance = utils.CaseInsensitiveDict({'FOO': 'bar'})
-        self.assertEqual(instance['foo'], 'bar')
-
-    def test_update_from_other_mapping(self):
-        """Tests updating the dictionary from another mapping."""
-        instance = utils.CaseInsensitiveDict()
-        instance.update({'FOO': 'bar'})
-        self.assertEqual(instance['foo'], 'bar')
diff --git a/tests/helpers.py b/tests/helpers.py
index 8e13f0f28..2b79a6c2a 100644
--- a/tests/helpers.py
+++ b/tests/helpers.py
@@ -315,7 +315,7 @@ class MockTextChannel(CustomMockMixin, unittest.mock.Mock, HashableMixin):
     """
     spec_set = channel_instance
 
-    def __init__(self, name: str = 'channel', channel_id: int = 1, **kwargs) -> None:
+    def __init__(self, **kwargs) -> None:
         default_kwargs = {'id': next(self.discord_id), 'name': 'channel', 'guild': MockGuild()}
         super().__init__(**collections.ChainMap(kwargs, default_kwargs))
 
@@ -323,6 +323,27 @@ class MockTextChannel(CustomMockMixin, unittest.mock.Mock, HashableMixin):
             self.mention = f"#{self.name}"
 
 
+# Create data for the DMChannel instance
+state = unittest.mock.MagicMock()
+me = unittest.mock.MagicMock()
+dm_channel_data = {"id": 1, "recipients": [unittest.mock.MagicMock()]}
+dm_channel_instance = discord.DMChannel(me=me, state=state, data=dm_channel_data)
+
+
+class MockDMChannel(CustomMockMixin, unittest.mock.Mock, HashableMixin):
+    """
+    A MagicMock subclass to mock TextChannel objects.
+
+    Instances of this class will follow the specifications of `discord.TextChannel` instances. For
+    more information, see the `MockGuild` docstring.
+    """
+    spec_set = dm_channel_instance
+
+    def __init__(self, **kwargs) -> None:
+        default_kwargs = {'id': next(self.discord_id), 'recipient': MockUser(), "me": MockUser()}
+        super().__init__(**collections.ChainMap(kwargs, default_kwargs))
+
+
 # Create a Message instance to get a realistic MagicMock of `discord.Message`
 message_data = {
     'id': 1,