Merge branch 'master' into help_channel_rediscache

21 files changed, 585 insertions, 243 deletions

diff --git a/.github/workflows/codeql-analysis.yml b/.github/workflows/codeql-analysis.yml
new file mode 100644
index 000000000..8760b35ec
--- /dev/null
+++ b/.github/workflows/codeql-analysis.yml
@@ -0,0 +1,32 @@
+name: "Code scanning - action"
+
+on:
+  push:
+  pull_request:
+  schedule:
+    - cron: '0 12 * * *'
+
+jobs:
+  CodeQL-Build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout repository
+      uses: actions/checkout@v2
+      with:
+        fetch-depth: 2
+
+    - run: git checkout HEAD^2
+      if: ${{ github.event_name == 'pull_request' }}
+
+    - name: Initialize CodeQL
+      uses: github/codeql-action/init@v1
+      with:
+        languages: python
+
+    - name: Autobuild
+      uses: github/codeql-action/autobuild@v1
+
+    - name: Perform CodeQL Analysis
+      uses: github/codeql-action/analyze@v1
diff --git a/bot/cogs/filtering.py b/bot/cogs/filtering.py
index 1d9fddb12..4ebc831e1 100644
--- a/bot/cogs/filtering.py
+++ b/bot/cogs/filtering.py
@@ -1,6 +1,8 @@
+import asyncio
 import logging
 import re
-from typing import Optional, Union
+from datetime import datetime, timedelta
+from typing import List, Optional, Union
 
 import discord.errors
 from dateutil.relativedelta import relativedelta
@@ -14,6 +16,7 @@ from bot.constants import (
     Channels, Colours,
     Filter, Icons, URLs
 )
+from bot.utils.redis_cache import RedisCache
 
 log = logging.getLogger(__name__)
 
@@ -40,6 +43,8 @@ TOKEN_WATCHLIST_PATTERNS = [
 ]
 WATCHLIST_PATTERNS = WORD_WATCHLIST_PATTERNS + TOKEN_WATCHLIST_PATTERNS
 
+DAYS_BETWEEN_ALERTS = 3
+
 
 def expand_spoilers(text: str) -> str:
     """Return a string containing all interpretations of a spoilered message."""
@@ -52,8 +57,12 @@ def expand_spoilers(text: str) -> str:
 class Filtering(Cog):
     """Filtering out invites, blacklisting domains, and warning us of certain regular expressions."""
 
+    # Redis cache mapping a user ID to the last timestamp a bad nickname alert was sent
+    name_alerts = RedisCache()
+
     def __init__(self, bot: Bot):
         self.bot = bot
+        self.name_lock = asyncio.Lock()
 
         staff_mistake_str = "If you believe this was a mistake, please let staff know!"
         self.filters = {
@@ -112,6 +121,7 @@ class Filtering(Cog):
     async def on_message(self, msg: Message) -> None:
         """Invoke message filter for new messages."""
         await self._filter_message(msg)
+        await self.check_bad_words_in_name(msg.author)
 
     @Cog.listener()
     async def on_message_edit(self, before: Message, after: Message) -> None:
@@ -126,6 +136,55 @@ class Filtering(Cog):
             delta = relativedelta(after.edited_at, before.edited_at).microseconds
         await self._filter_message(after, delta)
 
+    @staticmethod
+    def get_name_matches(name: str) -> List[re.Match]:
+        """Check bad words from passed string (name). Return list of matches."""
+        matches = []
+        for pattern in WATCHLIST_PATTERNS:
+            if match := pattern.search(name):
+                matches.append(match)
+        return matches
+
+    async def check_send_alert(self, member: Member) -> bool:
+        """When there is less than 3 days after last alert, return `False`, otherwise `True`."""
+        if last_alert := await self.name_alerts.get(member.id):
+            last_alert = datetime.utcfromtimestamp(last_alert)
+            if datetime.utcnow() - timedelta(days=DAYS_BETWEEN_ALERTS) < last_alert:
+                log.trace(f"Last alert was too recent for {member}'s nickname.")
+                return False
+
+        return True
+
+    async def check_bad_words_in_name(self, member: Member) -> None:
+        """Send a mod alert every 3 days if a username still matches a watchlist pattern."""
+        # Use lock to avoid race conditions
+        async with self.name_lock:
+            # Check whether the users display name contains any words in our blacklist
+            matches = self.get_name_matches(member.display_name)
+
+            if not matches or not await self.check_send_alert(member):
+                return
+
+            log.info(f"Sending bad nickname alert for '{member.display_name}' ({member.id}).")
+
+            log_string = (
+                f"**User:** {member.mention} (`{member.id}`)\n"
+                f"**Display Name:** {member.display_name}\n"
+                f"**Bad Matches:** {', '.join(match.group() for match in matches)}"
+            )
+
+            await self.mod_log.send_log_message(
+                icon_url=Icons.token_removed,
+                colour=Colours.soft_red,
+                title="Username filtering alert",
+                text=log_string,
+                channel_id=Channels.mod_alerts,
+                thumbnail=member.avatar_url
+            )
+
+            # Update time when alert sent
+            await self.name_alerts.set(member.id, datetime.utcnow().timestamp())
+
     async def _filter_message(self, msg: Message, delta: Optional[int] = None) -> None:
         """Filter the input message to see if it violates any of our rules, and then respond accordingly."""
         # Should we filter this message?
diff --git a/bot/cogs/help_channels.py b/bot/cogs/help_channels.py
index 4c464a7d2..187adfe51 100644
--- a/bot/cogs/help_channels.py
+++ b/bot/cogs/help_channels.py
@@ -22,7 +22,7 @@ log = logging.getLogger(__name__)
 
 ASKING_GUIDE_URL = "https://pythondiscord.com/pages/asking-good-questions/"
 MAX_CHANNELS_PER_CATEGORY = 50
-EXCLUDED_CHANNELS = (constants.Channels.how_to_get_help,)
+EXCLUDED_CHANNELS = (constants.Channels.how_to_get_help, constants.Channels.cooldown)
 
 HELP_CHANNEL_TOPIC = """
 This is a Python help channel. You can claim your own help channel in the Python Help: Available category.
diff --git a/bot/cogs/moderation/modlog.py b/bot/cogs/moderation/modlog.py
index 9d28030d9..41472c64c 100644
--- a/bot/cogs/moderation/modlog.py
+++ b/bot/cogs/moderation/modlog.py
@@ -555,6 +555,10 @@ class ModLog(Cog, name="ModLog"):
         channel = message.channel
         author = message.author
 
+        # Ignore DMs.
+        if not message.guild:
+            return
+
         if message.guild.id != GuildConstant.id or channel.id in GuildConstant.modlog_blacklist:
             return
 
diff --git a/bot/cogs/moderation/silence.py b/bot/cogs/moderation/silence.py
index 25febfa51..c8ab6443b 100644
--- a/bot/cogs/moderation/silence.py
+++ b/bot/cogs/moderation/silence.py
@@ -1,7 +1,7 @@
 import asyncio
 import logging
 from contextlib import suppress
-from typing import Optional
+from typing import NamedTuple, Optional
 
 from discord import TextChannel
 from discord.ext import commands, tasks
@@ -11,10 +11,18 @@ from bot.bot import Bot
 from bot.constants import Channels, Emojis, Guild, MODERATION_ROLES, Roles
 from bot.converters import HushDurationConverter
 from bot.utils.checks import with_role_check
+from bot.utils.scheduling import Scheduler
 
 log = logging.getLogger(__name__)
 
 
+class TaskData(NamedTuple):
+    """Data for a scheduled task."""
+
+    delay: int
+    ctx: Context
+
+
 class SilenceNotifier(tasks.Loop):
     """Loop notifier for posting notices to `alert_channel` containing added channels."""
 
@@ -53,15 +61,25 @@ class SilenceNotifier(tasks.Loop):
             await self._alert_channel.send(f"<@&{Roles.moderators}> currently silenced channels: {channels_text}")
 
 
-class Silence(commands.Cog):
+class Silence(Scheduler, commands.Cog):
     """Commands for stopping channel messages for `verified` role in a channel."""
 
     def __init__(self, bot: Bot):
+        super().__init__()
         self.bot = bot
         self.muted_channels = set()
         self._get_instance_vars_task = self.bot.loop.create_task(self._get_instance_vars())
         self._get_instance_vars_event = asyncio.Event()
 
+    async def _scheduled_task(self, task: TaskData) -> None:
+        """Calls `self.unsilence` on expired silenced channel to unsilence it."""
+        await asyncio.sleep(task.delay)
+        log.info("Unsilencing channel after set delay.")
+
+        # Because `self.unsilence` explicitly cancels this scheduled task, it is shielded
+        # to avoid prematurely cancelling itself
+        await asyncio.shield(task.ctx.invoke(self.unsilence))
+
     async def _get_instance_vars(self) -> None:
         """Get instance variables after they're available to get from the guild."""
         await self.bot.wait_until_guild_available()
@@ -90,9 +108,13 @@ class Silence(commands.Cog):
             return
 
         await ctx.send(f"{Emojis.check_mark} silenced current channel for {duration} minute(s).")
-        await asyncio.sleep(duration*60)
-        log.info("Unsilencing channel after set delay.")
-        await ctx.invoke(self.unsilence)
+
+        task_data = TaskData(
+            delay=duration*60,
+            ctx=ctx
+        )
+
+        self.schedule_task(ctx.channel.id, task_data)
 
     @commands.command(aliases=("unhush",))
     async def unsilence(self, ctx: Context) -> None:
@@ -103,7 +125,9 @@ class Silence(commands.Cog):
         """
         await self._get_instance_vars_event.wait()
         log.debug(f"Unsilencing channel #{ctx.channel} from {ctx.author}'s command.")
-        if await self._unsilence(ctx.channel):
+        if not await self._unsilence(ctx.channel):
+            await ctx.send(f"{Emojis.cross_mark} current channel was not silenced.")
+        else:
             await ctx.send(f"{Emojis.check_mark} unsilenced current channel.")
 
     async def _silence(self, channel: TextChannel, persistent: bool, duration: Optional[int]) -> bool:
@@ -140,6 +164,7 @@ class Silence(commands.Cog):
         if current_overwrite.send_messages is False:
             await channel.set_permissions(self._verified_role, **dict(current_overwrite, send_messages=None))
             log.info(f"Unsilenced channel #{channel} ({channel.id}).")
+            self.cancel_task(channel.id)
             self.notifier.remove_channel(channel)
             self.muted_channels.discard(channel)
             return True
diff --git a/bot/cogs/site.py b/bot/cogs/site.py
index e61cd5003..ac29daa1d 100644
--- a/bot/cogs/site.py
+++ b/bot/cogs/site.py
@@ -33,7 +33,7 @@ class Site(Cog):
         embed.colour = Colour.blurple()
         embed.description = (
             f"[Our official website]({url}) is an open-source community project "
-            "created with Python and Flask. It contains information about the server "
+            "created with Python and Django. It contains information about the server "
             "itself, lets you sign up for upcoming events, has its own wiki, contains "
             "a list of valuable learning resources, and much more."
         )
diff --git a/bot/cogs/stats.py b/bot/cogs/stats.py
index 4ebb6423c..d42f55466 100644
--- a/bot/cogs/stats.py
+++ b/bot/cogs/stats.py
@@ -36,7 +36,8 @@ class Stats(Cog):
         if message.guild.id != Guild.id:
             return
 
-        if message.channel.category.id == Categories.modmail:
+        cat = getattr(message.channel, "category", None)
+        if cat is not None and cat.id == Categories.modmail:
             if message.channel.id != Channels.incidents:
                 # Do not report modmail channels to stats, there are too many
                 # of them for interesting statistics to be drawn out of this.
diff --git a/bot/cogs/token_remover.py b/bot/cogs/token_remover.py
index 6721f0e02..d55e079e9 100644
--- a/bot/cogs/token_remover.py
+++ b/bot/cogs/token_remover.py
@@ -2,20 +2,22 @@ import base64
 import binascii
 import logging
 import re
-import struct
 import typing as t
-from datetime import datetime
 
 from discord import Colour, Message
 from discord.ext.commands import Cog
-from discord.utils import snowflake_time
 
+from bot import utils
 from bot.bot import Bot
 from bot.cogs.moderation import ModLog
 from bot.constants import Channels, Colours, Event, Icons
 
 log = logging.getLogger(__name__)
 
+LOG_MESSAGE = (
+    "Censored a seemingly valid token sent by {author} (`{author_id}`) in {channel}, "
+    "token was `{user_id}.{timestamp}.{hmac}`"
+)
 DELETION_MESSAGE_TEMPLATE = (
     "Hey {mention}! I noticed you posted a seemingly valid Discord API "
     "token in your message and have removed your message. "
@@ -25,15 +27,22 @@ DELETION_MESSAGE_TEMPLATE = (
     "Feel free to re-post it with the token removed. "
     "If you believe this was a mistake, please let us know!"
 )
-DISCORD_EPOCH_TIMESTAMP = datetime(2017, 1, 1)
+DISCORD_EPOCH = 1_420_070_400
 TOKEN_EPOCH = 1_293_840_000
-TOKEN_RE = re.compile(
-    r"[^\s\.()\"']+"  # Matches token part 1: The user ID string, encoded as base64
-    r"\."             # Matches a literal dot between the token parts
-    r"[^\s\.()\"']+"  # Matches token part 2: The creation timestamp, as an integer
-    r"\."             # Matches a literal dot between the token parts
-    r"[^\s\.()\"']+"  # Matches token part 3: The HMAC, unused by us, but check that it isn't empty
-)
+
+# Three parts delimited by dots: user ID, creation timestamp, HMAC.
+# The HMAC isn't parsed further, but it's in the regex to ensure it at least exists in the string.
+# Each part only matches base64 URL-safe characters.
+# Padding has never been observed, but the padding character '=' is matched just in case.
+TOKEN_RE = re.compile(r"([\w\-=]+)\.([\w\-=]+)\.([\w\-=]+)", re.ASCII)
+
+
+class Token(t.NamedTuple):
+    """A Discord Bot token."""
+
+    user_id: str
+    timestamp: str
+    hmac: str
 
 
 class TokenRemover(Cog):
@@ -65,64 +74,58 @@ class TokenRemover(Cog):
 
         See: https://discordapp.com/developers/docs/reference#snowflakes
         """
-        found_token = self.find_token_in_message(after)
-        if found_token:
-            await self.take_action(after, found_token)
+        await self.on_message(after)
 
-    async def take_action(self, msg: Message, found_token: str) -> None:
-        """Remove the `msg` containing a token an send a mod_log message."""
-        user_id, creation_timestamp, hmac = found_token.split('.')
+    async def take_action(self, msg: Message, found_token: Token) -> None:
+        """Remove the `msg` containing the `found_token` and send a mod log message."""
         self.mod_log.ignore(Event.message_delete, msg.id)
         await msg.delete()
         await msg.channel.send(DELETION_MESSAGE_TEMPLATE.format(mention=msg.author.mention))
 
-        message = (
-            "Censored a seemingly valid token sent by "
-            f"{msg.author} (`{msg.author.id}`) in {msg.channel.mention}, token was "
-            f"`{user_id}.{creation_timestamp}.{'x' * len(hmac)}`"
-        )
-        log.debug(message)
+        log_message = self.format_log_message(msg, found_token)
+        log.debug(log_message)
 
         # Send pretty mod log embed to mod-alerts
         await self.mod_log.send_log_message(
             icon_url=Icons.token_removed,
             colour=Colour(Colours.soft_red),
             title="Token removed!",
-            text=message,
+            text=log_message,
             thumbnail=msg.author.avatar_url_as(static_format="png"),
             channel_id=Channels.mod_alerts,
         )
 
         self.bot.stats.incr("tokens.removed_tokens")
 
+    @staticmethod
+    def format_log_message(msg: Message, token: Token) -> str:
+        """Return the log message to send for `token` being censored in `msg`."""
+        return LOG_MESSAGE.format(
+            author=msg.author,
+            author_id=msg.author.id,
+            channel=msg.channel.mention,
+            user_id=token.user_id,
+            timestamp=token.timestamp,
+            hmac='x' * len(token.hmac),
+        )
+
     @classmethod
-    def find_token_in_message(cls, msg: Message) -> t.Optional[str]:
+    def find_token_in_message(cls, msg: Message) -> t.Optional[Token]:
         """Return a seemingly valid token found in `msg` or `None` if no token is found."""
         if msg.author.bot:
             return
 
-        # Use findall rather than search to guard against method calls prematurely returning the
+        # Use finditer rather than search to guard against method calls prematurely returning the
         # token check (e.g. `message.channel.send` also matches our token pattern)
-        maybe_matches = TOKEN_RE.findall(msg.content)
-        for substr in maybe_matches:
-            if cls.is_maybe_token(substr):
+        for match in TOKEN_RE.finditer(msg.content):
+            token = Token(*match.groups())
+            if cls.is_valid_user_id(token.user_id) and cls.is_valid_timestamp(token.timestamp):
                 # Short-circuit on first match
-                return substr
+                return token
 
         # No matching substring
         return
 
-    @classmethod
-    def is_maybe_token(cls, test_str: str) -> bool:
-        """Check the provided string to see if it is a seemingly valid token."""
-        try:
-            user_id, creation_timestamp, hmac = test_str.split('.')
-        except ValueError:
-            return False
-
-        if cls.is_valid_user_id(user_id) and cls.is_valid_timestamp(creation_timestamp):
-            return True
-
     @staticmethod
     def is_valid_user_id(b64_content: str) -> bool:
         """
@@ -130,29 +133,41 @@ class TokenRemover(Cog):
 
         See: https://discordapp.com/developers/docs/reference#snowflakes
         """
-        b64_content += '=' * (-len(b64_content) % 4)
+        b64_content = utils.pad_base64(b64_content)
 
         try:
-            content: bytes = base64.b64decode(b64_content)
-            return content.decode('utf-8').isnumeric()
-        except (binascii.Error, UnicodeDecodeError):
+            decoded_bytes = base64.urlsafe_b64decode(b64_content)
+            string = decoded_bytes.decode('utf-8')
+
+            # isdigit on its own would match a lot of other Unicode characters, hence the isascii.
+            return string.isascii() and string.isdigit()
+        except (binascii.Error, ValueError):
             return False
 
     @staticmethod
     def is_valid_timestamp(b64_content: str) -> bool:
         """
-        Check potential token to see if it contains a valid timestamp.
+        Return True if `b64_content` decodes to a valid timestamp.
 
-        See: https://discordapp.com/developers/docs/reference#snowflakes
+        If the timestamp is greater than the Discord epoch, it's probably valid.
+        See: https://i.imgur.com/7WdehGn.png
         """
-        b64_content += '=' * (-len(b64_content) % 4)
+        b64_content = utils.pad_base64(b64_content)
 
         try:
-            content = base64.urlsafe_b64decode(b64_content)
-            snowflake = struct.unpack('i', content)[0]
-        except (binascii.Error, struct.error):
+            decoded_bytes = base64.urlsafe_b64decode(b64_content)
+            timestamp = int.from_bytes(decoded_bytes, byteorder="big")
+        except (binascii.Error, ValueError) as e:
+            log.debug(f"Failed to decode token timestamp '{b64_content}': {e}")
+            return False
+
+        # Seems like newer tokens don't need the epoch added, but add anyway since an upper bound
+        # is not checked.
+        if timestamp + TOKEN_EPOCH >= DISCORD_EPOCH:
+            return True
+        else:
+            log.debug(f"Invalid token timestamp '{b64_content}': smaller than Discord epoch")
             return False
-        return snowflake_time(snowflake + TOKEN_EPOCH) < DISCORD_EPOCH_TIMESTAMP
 
 
 def setup(bot: Bot) -> None:
diff --git a/bot/cogs/utils.py b/bot/cogs/utils.py
index 73b4a1c0a..697bf60ce 100644
--- a/bot/cogs/utils.py
+++ b/bot/cogs/utils.py
@@ -6,7 +6,7 @@ from email.parser import HeaderParser
 from io import StringIO
 from typing import Tuple, Union
 
-from discord import Colour, Embed
+from discord import Colour, Embed, utils
 from discord.ext.commands import BadArgument, Cog, Context, command
 
 from bot.bot import Bot
@@ -145,7 +145,7 @@ class Utils(Cog):
                 u_code = f"\\U{digit:>08}"
             url = f"https://www.compart.com/en/unicode/U+{digit:>04}"
             name = f"[{unicodedata.name(char, '')}]({url})"
-            info = f"`{u_code.ljust(10)}`: {name} - {char}"
+            info = f"`{u_code.ljust(10)}`: {name} - {utils.escape_markdown(char)}"
             return info, u_code
 
         charlist, rawlist = zip(*(get_info(c) for c in characters))
diff --git a/bot/constants.py b/bot/constants.py
index b31a9c99e..470221369 100644
--- a/bot/constants.py
+++ b/bot/constants.py
@@ -389,6 +389,7 @@ class Channels(metaclass=YAMLGetter):
     attachment_log: int
     big_brother_logs: int
     bot_commands: int
+    cooldown: int
     defcon: int
     dev_contrib: int
     dev_core: int
diff --git a/bot/converters.py b/bot/converters.py
index 72c46fdf0..4deb59f87 100644
--- a/bot/converters.py
+++ b/bot/converters.py
@@ -217,7 +217,10 @@ class Duration(Converter):
         delta = relativedelta(**duration_dict)
         now = datetime.utcnow()
 
-        return now + delta
+        try:
+            return now + delta
+        except ValueError:
+            raise BadArgument(f"`{duration}` results in a datetime outside the supported range.")
 
 
 class ISODateTime(Converter):
diff --git a/bot/utils/__init__.py b/bot/utils/__init__.py
index c5a12d5e3..5a6e1811b 100644
--- a/bot/utils/__init__.py
+++ b/bot/utils/__init__.py
@@ -11,3 +11,8 @@ class CogABCMeta(CogMeta, ABCMeta):
     """Metaclass for ABCs meant to be implemented as Cogs."""
 
     pass
+
+
+def pad_base64(data: str) -> str:
+    """Return base64 `data` with padding characters to ensure its length is a multiple of 4."""
+    return data + "=" * (-len(data) % 4)
diff --git a/bot/utils/messages.py b/bot/utils/messages.py
index de8e186f3..23519a514 100644
--- a/bot/utils/messages.py
+++ b/bot/utils/messages.py
@@ -97,7 +97,7 @@ async def send_attachments(
             if link_large and e.status == 413:
                 large.append(attachment)
             else:
-                log.warning(f"{failure_msg} with status {e.status}.")
+                log.warning(f"{failure_msg} with status {e.status}.", exc_info=e)
 
     if link_large and large:
         desc = "\n".join(f"[{attachment.filename}]({attachment.url})" for attachment in large)
diff --git a/bot/utils/redis_cache.py b/bot/utils/redis_cache.py
index f342bbb62..58cfe1df5 100644
--- a/bot/utils/redis_cache.py
+++ b/bot/utils/redis_cache.py
@@ -101,16 +101,7 @@ class RedisCache:
 
     def _set_namespace(self, namespace: str) -> None:
         """Try to set the namespace, but do not permit collisions."""
-        # We need a unique namespace, to prevent collisions. This loop
-        # will try appending underscores to the end of the namespace until
-        # it finds one that is unique.
-        #
-        # For example, if `john` and `john_`  are both taken, the namespace will
-        # be `john__` at the end of this loop.
-        while namespace in self._namespaces:
-            namespace += "_"
-
-        log.trace(f"RedisCache setting namespace to {self._namespace}")
+        log.trace(f"RedisCache setting namespace to {namespace}")
         self._namespaces.append(namespace)
         self._namespace = namespace
 
diff --git a/config-default.yml b/config-default.yml
index 2c85f5ef3..aff5fb2e1 100644
--- a/config-default.yml
+++ b/config-default.yml
@@ -142,6 +142,7 @@ guild:
 
         # Python Help: Available
         how_to_get_help:    704250143020417084
+        cooldown:           720603994149486673
 
         # Logs
         attachment_log:     &ATTACH_LOG     649243850006855680
@@ -297,6 +298,8 @@ filter:
         - 613425648685547541  # Discord Developers
         - 185590609631903755  # Blender Hub
         - 420324994703163402  # /r/FlutterDev
+        - 488751051629920277  # Python Atlanta
+        - 143867839282020352  # C#
 
     domain_blacklist:
         - pornhub.com
diff --git a/docker-compose.yml b/docker-compose.yml
index 9884e35f0..cff7d33d6 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -17,6 +17,14 @@ services:
     ports:
       - "127.0.0.1:6379:6379"
 
+  snekbox:
+    image: pythondiscord/snekbox:latest
+    init: true
+    ipc: none
+    ports:
+     - "127.0.0.1:8060:8060"
+    privileged: true
+
   web:
     image: pythondiscord/site:latest
     command: ["run", "--debug"]
@@ -47,6 +55,7 @@ services:
     depends_on:
       - web
       - redis
+      - snekbox
     environment:
       BOT_TOKEN: ${BOT_TOKEN}
       BOT_API_KEY: badbot13m0n8f570f942013fc818f234916ca531
diff --git a/tests/bot/cogs/moderation/test_silence.py b/tests/bot/cogs/moderation/test_silence.py
index 3fd149f04..ab3d0742a 100644
--- a/tests/bot/cogs/moderation/test_silence.py
+++ b/tests/bot/cogs/moderation/test_silence.py
@@ -127,10 +127,20 @@ class SilenceTests(unittest.IsolatedAsyncioTestCase):
             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.")
+        """Check if proper message was sent when unsilencing channel."""
+        test_cases = (
+            (True, f"{Emojis.check_mark} unsilenced current channel."),
+            (False, f"{Emojis.cross_mark} current channel was not silenced.")
+        )
+        for _unsilence_patch_return, result_message in test_cases:
+            with self.subTest(
+                starting_silenced_state=_unsilence_patch_return,
+                result_message=result_message
+            ):
+                with mock.patch.object(self.cog, "_unsilence", return_value=_unsilence_patch_return):
+                    await self.cog.unsilence.callback(self.cog, self.ctx)
+                    self.ctx.send.assert_called_once_with(result_message)
+            self.ctx.reset_mock()
 
     async def test_silence_private_for_false(self):
         """Permissions are not set and `False` is returned in an already silenced channel."""
diff --git a/tests/bot/cogs/test_token_remover.py b/tests/bot/cogs/test_token_remover.py
index 33d1ec170..a10124d2d 100644
--- a/tests/bot/cogs/test_token_remover.py
+++ b/tests/bot/cogs/test_token_remover.py
@@ -1,56 +1,89 @@
-import asyncio
-import logging
 import unittest
-from unittest.mock import AsyncMock, MagicMock
+from re import Match
+from unittest import mock
+from unittest.mock import MagicMock
 
 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 MockBot, MockMessage
+from bot import constants
+from bot.cogs import token_remover
+from bot.cogs.moderation import ModLog
+from bot.cogs.token_remover import Token, TokenRemover
+from tests.helpers import MockBot, MockMessage, autospec
 
 
-class TokenRemoverTests(unittest.TestCase):
+class TokenRemoverTests(unittest.IsolatedAsyncioTestCase):
     """Tests the `TokenRemover` cog."""
 
     def setUp(self):
         """Adds the cog, a bot, and a message to the instance for usage in tests."""
         self.bot = MockBot()
-        self.bot.get_cog.return_value = MagicMock()
-        self.bot.get_cog.return_value.send_log_message = AsyncMock()
         self.cog = TokenRemover(bot=self.bot)
 
-        self.msg = MockMessage(id=555, content='')
-        self.msg.author.__str__ = MagicMock()
-        self.msg.author.__str__.return_value = 'lemon'
-        self.msg.author.bot = False
-        self.msg.author.avatar_url_as.return_value = 'picture-lemon.png'
-        self.msg.author.id = 42
-        self.msg.author.mention = '@lemon'
+        self.msg = MockMessage(id=555, content="hello world")
         self.msg.channel.mention = "#lemonade-stand"
+        self.msg.author.__str__ = MagicMock(return_value=self.msg.author.name)
+        self.msg.author.avatar_url_as.return_value = "picture-lemon.png"
 
-    def test_is_valid_user_id_is_true_for_numeric_content(self):
-        """A string decoding to numeric characters is a valid user ID."""
-        # MTIz = base64(123)
-        self.assertTrue(TokenRemover.is_valid_user_id('MTIz'))
+    def test_is_valid_user_id_valid(self):
+        """Should consider user IDs valid if they decode entirely to ASCII digits."""
+        ids = (
+            "NDcyMjY1OTQzMDYyNDEzMzMy",
+            "NDc1MDczNjI5Mzk5NTQ3OTA0",
+            "NDY3MjIzMjMwNjUwNzc3NjQx",
+        )
+
+        for user_id in ids:
+            with self.subTest(user_id=user_id):
+                result = TokenRemover.is_valid_user_id(user_id)
+                self.assertTrue(result)
 
-    def test_is_valid_user_id_is_false_for_alphabetic_content(self):
-        """A string decoding to alphabetic characters is not a valid user ID."""
-        # YWJj = base64(abc)
-        self.assertFalse(TokenRemover.is_valid_user_id('YWJj'))
+    def test_is_valid_user_id_invalid(self):
+        """Should consider non-digit and non-ASCII IDs invalid."""
+        ids = (
+            ("SGVsbG8gd29ybGQ", "non-digit ASCII"),
+            ("0J_RgNC40LLQtdGCINC80LjRgA", "cyrillic text"),
+            ("4pO14p6L4p6C4pG34p264pGl8J-EiOKSj-KCieKBsA", "Unicode digits"),
+            ("4oaA4oaB4oWh4oWi4Lyz4Lyq4Lyr4LG9", "Unicode numerals"),
+            ("8J2fjvCdn5nwnZ-k8J2fr_Cdn7rgravvvJngr6c", "Unicode decimals"),
+            ("{hello}[world]&(bye!)", "ASCII invalid Base64"),
+            ("Þíß-ï§-ňøẗ-våłìÐ", "Unicode invalid Base64"),
+        )
 
-    def test_is_valid_timestamp_is_true_for_valid_timestamps(self):
-        """A string decoding to a valid timestamp should be recognized as such."""
-        self.assertTrue(TokenRemover.is_valid_timestamp('DN9r_A'))
+        for user_id, msg in ids:
+            with self.subTest(msg=msg):
+                result = TokenRemover.is_valid_user_id(user_id)
+                self.assertFalse(result)
 
-    def test_is_valid_timestamp_is_false_for_invalid_values(self):
-        """A string not decoding to a valid timestamp should not be recognized as such."""
-        # MTIz = base64(123)
-        self.assertFalse(TokenRemover.is_valid_timestamp('MTIz'))
+    def test_is_valid_timestamp_valid(self):
+        """Should consider timestamps valid if they're greater than the Discord epoch."""
+        timestamps = (
+            "XsyRkw",
+            "Xrim9Q",
+            "XsyR-w",
+            "XsySD_",
+            "Dn9r_A",
+        )
+
+        for timestamp in timestamps:
+            with self.subTest(timestamp=timestamp):
+                result = TokenRemover.is_valid_timestamp(timestamp)
+                self.assertTrue(result)
+
+    def test_is_valid_timestamp_invalid(self):
+        """Should consider timestamps invalid if they're before Discord epoch or can't be parsed."""
+        timestamps = (
+            ("B4Yffw", "DISCORD_EPOCH - TOKEN_EPOCH - 1"),
+            ("ew", "123"),
+            ("AoIKgA", "42076800"),
+            ("{hello}[world]&(bye!)", "ASCII invalid Base64"),
+            ("Þíß-ï§-ňøẗ-våłìÐ", "Unicode invalid Base64"),
+        )
+
+        for timestamp, msg in timestamps:
+            with self.subTest(msg=msg):
+                result = TokenRemover.is_valid_timestamp(timestamp)
+                self.assertFalse(result)
 
     def test_mod_log_property(self):
         """The `mod_log` property should ask the bot to return the `ModLog` cog."""
@@ -58,74 +91,206 @@ class TokenRemoverTests(unittest.TestCase):
         self.assertEqual(self.cog.mod_log, self.bot.get_cog.return_value)
         self.bot.get_cog.assert_called_once_with('ModLog')
 
-    def test_ignores_bot_messages(self):
-        """When the message event handler is called with a bot message, nothing is done."""
+    async def test_on_message_edit_uses_on_message(self):
+        """The edit listener should delegate handling of the message to the normal listener."""
+        self.cog.on_message = mock.create_autospec(self.cog.on_message, spec_set=True)
+
+        await self.cog.on_message_edit(MockMessage(), self.msg)
+        self.cog.on_message.assert_awaited_once_with(self.msg)
+
+    @autospec(TokenRemover, "find_token_in_message", "take_action")
+    async def test_on_message_takes_action(self, find_token_in_message, take_action):
+        """Should take action if a valid token is found when a message is sent."""
+        cog = TokenRemover(self.bot)
+        found_token = "foobar"
+        find_token_in_message.return_value = found_token
+
+        await cog.on_message(self.msg)
+
+        find_token_in_message.assert_called_once_with(self.msg)
+        take_action.assert_awaited_once_with(cog, self.msg, found_token)
+
+    @autospec(TokenRemover, "find_token_in_message", "take_action")
+    async def test_on_message_skips_missing_token(self, find_token_in_message, take_action):
+        """Shouldn't take action if a valid token isn't found when a message is sent."""
+        cog = TokenRemover(self.bot)
+        find_token_in_message.return_value = False
+
+        await cog.on_message(self.msg)
+
+        find_token_in_message.assert_called_once_with(self.msg)
+        take_action.assert_not_awaited()
+
+    @autospec("bot.cogs.token_remover", "TOKEN_RE")
+    def test_find_token_ignores_bot_messages(self, token_re):
+        """The token finder should ignore messages authored by bots."""
         self.msg.author.bot = True
-        coroutine = self.cog.on_message(self.msg)
-        self.assertIsNone(asyncio.run(coroutine))
-
-    def test_ignores_messages_without_tokens(self):
-        """Messages without anything looking like a token are ignored."""
-        for content in ('', 'lemon wins'):
-            with self.subTest(content=content):
-                self.msg.content = content
-                coroutine = self.cog.on_message(self.msg)
-                self.assertIsNone(asyncio.run(coroutine))
-
-    def test_ignores_messages_with_invalid_tokens(self):
-        """Messages with values that are invalid tokens are ignored."""
-        for content in ('foo.bar.baz', 'x.y.'):
-            with self.subTest(content=content):
-                self.msg.content = content
-                coroutine = self.cog.on_message(self.msg)
-                self.assertIsNone(asyncio.run(coroutine))
-
-    def test_censors_valid_tokens(self):
-        """Valid tokens are censored."""
-        cases = (
-            # (content, censored_token)
-            ('MTIz.DN9R_A.xyz', 'MTIz.DN9R_A.xxx'),
+
+        return_value = TokenRemover.find_token_in_message(self.msg)
+
+        self.assertIsNone(return_value)
+        token_re.finditer.assert_not_called()
+
+    @autospec("bot.cogs.token_remover", "TOKEN_RE")
+    def test_find_token_no_matches(self, token_re):
+        """None should be returned if the regex matches no tokens in a message."""
+        token_re.finditer.return_value = ()
+
+        return_value = TokenRemover.find_token_in_message(self.msg)
+
+        self.assertIsNone(return_value)
+        token_re.finditer.assert_called_once_with(self.msg.content)
+
+    @autospec(TokenRemover, "is_valid_user_id", "is_valid_timestamp")
+    @autospec("bot.cogs.token_remover", "Token")
+    @autospec("bot.cogs.token_remover", "TOKEN_RE")
+    def test_find_token_valid_match(self, token_re, token_cls, is_valid_id, is_valid_timestamp):
+        """The first match with a valid user ID and timestamp should be returned as a `Token`."""
+        matches = [
+            mock.create_autospec(Match, spec_set=True, instance=True),
+            mock.create_autospec(Match, spec_set=True, instance=True),
+        ]
+        tokens = [
+            mock.create_autospec(Token, spec_set=True, instance=True),
+            mock.create_autospec(Token, spec_set=True, instance=True),
+        ]
+
+        token_re.finditer.return_value = matches
+        token_cls.side_effect = tokens
+        is_valid_id.side_effect = (False, True)  # The 1st match will be invalid, 2nd one valid.
+        is_valid_timestamp.return_value = True
+
+        return_value = TokenRemover.find_token_in_message(self.msg)
+
+        self.assertEqual(tokens[1], return_value)
+        token_re.finditer.assert_called_once_with(self.msg.content)
+
+    @autospec(TokenRemover, "is_valid_user_id", "is_valid_timestamp")
+    @autospec("bot.cogs.token_remover", "Token")
+    @autospec("bot.cogs.token_remover", "TOKEN_RE")
+    def test_find_token_invalid_matches(self, token_re, token_cls, is_valid_id, is_valid_timestamp):
+        """None should be returned if no matches have valid user IDs or timestamps."""
+        token_re.finditer.return_value = [mock.create_autospec(Match, spec_set=True, instance=True)]
+        token_cls.return_value = mock.create_autospec(Token, spec_set=True, instance=True)
+        is_valid_id.return_value = False
+        is_valid_timestamp.return_value = False
+
+        return_value = TokenRemover.find_token_in_message(self.msg)
+
+        self.assertIsNone(return_value)
+        token_re.finditer.assert_called_once_with(self.msg.content)
+
+    def test_regex_invalid_tokens(self):
+        """Messages without anything looking like a token are not matched."""
+        tokens = (
+            "",
+            "lemon wins",
+            "..",
+            "x.y",
+            "x.y.",
+            ".y.z",
+            ".y.",
+            "..z",
+            "x..z",
+            " . . ",
+            "\n.\n.\n",
+            "hellö.world.bye",
+            "base64.nötbåse64.morebase64",
+            "19jd3J.dfkm3d.€víł§tüff",
+        )
+
+        for token in tokens:
+            with self.subTest(token=token):
+                results = token_remover.TOKEN_RE.findall(token)
+                self.assertEqual(len(results), 0)
+
+    def test_regex_valid_tokens(self):
+        """Messages that look like tokens should be matched."""
+        # Don't worry, these tokens have been invalidated.
+        tokens = (
+            "NDcyMjY1OTQzMDYy_DEzMz-y.XsyRkw.VXmErH7j511turNpfURmb0rVNm8",
+            "NDcyMjY1OTQzMDYyNDEzMzMy.Xrim9Q.Ysnu2wacjaKs7qnoo46S8Dm2us8",
+            "NDc1MDczNjI5Mzk5NTQ3OTA0.XsyR-w.sJf6omBPORBPju3WJEIAcwW9Zds",
+            "NDY3MjIzMjMwNjUwNzc3NjQx.XsySD_.s45jqDV_Iisn-symw0yDRrk_jf4",
         )
 
-        for content, censored_token in cases:
-            with self.subTest(content=content, censored_token=censored_token):
-                self.msg.content = content
-                coroutine = self.cog.on_message(self.msg)
-                with self.assertLogs(logger='bot.cogs.token_remover', level=logging.DEBUG) as cm:
-                    self.assertIsNone(asyncio.run(coroutine))  # no return value
-
-                [line] = cm.output
-                log_message = (
-                    "Censored a seemingly valid token sent by "
-                    "lemon (`42`) in #lemonade-stand, "
-                    f"token was `{censored_token}`"
-                )
-                self.assertIn(log_message, line)
-
-                self.msg.delete.assert_called_once_with()
-                self.msg.channel.send.assert_called_once_with(
-                    DELETION_MESSAGE_TEMPLATE.format(mention='@lemon')
-                )
-                self.bot.get_cog.assert_called_with('ModLog')
-                self.msg.author.avatar_url_as.assert_called_once_with(static_format='png')
-
-                mod_log = self.bot.get_cog.return_value
-                mod_log.ignore.assert_called_once_with(Event.message_delete, self.msg.id)
-                mod_log.send_log_message.assert_called_once_with(
-                    icon_url=Icons.token_removed,
-                    colour=Colour(Colours.soft_red),
-                    title="Token removed!",
-                    text=log_message,
-                    thumbnail='picture-lemon.png',
-                    channel_id=Channels.mod_alerts
-                )
-
-
-class TokenRemoverSetupTests(unittest.TestCase):
-    """Tests setup of the `TokenRemover` cog."""
-
-    def test_setup(self):
-        """Setup of the extension should call add_cog."""
+        for token in tokens:
+            with self.subTest(token=token):
+                results = token_remover.TOKEN_RE.fullmatch(token)
+                self.assertIsNotNone(results, f"{token} was not matched by the regex")
+
+    def test_regex_matches_multiple_valid(self):
+        """Should support multiple matches in the middle of a string."""
+        token_1 = "NDY3MjIzMjMwNjUwNzc3NjQx.XsyWGg.uFNEQPCc4ePwGh7egG8UicQssz8"
+        token_2 = "NDcyMjY1OTQzMDYyNDEzMzMy.XsyWMw.l8XPnDqb0lp-EiQ2g_0xVFT1pyc"
+        message = f"garbage {token_1} hello {token_2} world"
+
+        results = token_remover.TOKEN_RE.finditer(message)
+        results = [match[0] for match in results]
+        self.assertCountEqual((token_1, token_2), results)
+
+    @autospec("bot.cogs.token_remover", "LOG_MESSAGE")
+    def test_format_log_message(self, log_message):
+        """Should correctly format the log message with info from the message and token."""
+        token = Token("NDY3MjIzMjMwNjUwNzc3NjQx", "XsySD_", "s45jqDV_Iisn-symw0yDRrk_jf4")
+        log_message.format.return_value = "Howdy"
+
+        return_value = TokenRemover.format_log_message(self.msg, token)
+
+        self.assertEqual(return_value, log_message.format.return_value)
+        log_message.format.assert_called_once_with(
+            author=self.msg.author,
+            author_id=self.msg.author.id,
+            channel=self.msg.channel.mention,
+            user_id=token.user_id,
+            timestamp=token.timestamp,
+            hmac="x" * len(token.hmac),
+        )
+
+    @mock.patch.object(TokenRemover, "mod_log", new_callable=mock.PropertyMock)
+    @autospec("bot.cogs.token_remover", "log")
+    @autospec(TokenRemover, "format_log_message")
+    async def test_take_action(self, format_log_message, logger, mod_log_property):
+        """Should delete the message and send a mod log."""
+        cog = TokenRemover(self.bot)
+        mod_log = mock.create_autospec(ModLog, spec_set=True, instance=True)
+        token = mock.create_autospec(Token, spec_set=True, instance=True)
+        log_msg = "testing123"
+
+        mod_log_property.return_value = mod_log
+        format_log_message.return_value = log_msg
+
+        await cog.take_action(self.msg, token)
+
+        self.msg.delete.assert_called_once_with()
+        self.msg.channel.send.assert_called_once_with(
+            token_remover.DELETION_MESSAGE_TEMPLATE.format(mention=self.msg.author.mention)
+        )
+
+        format_log_message.assert_called_once_with(self.msg, token)
+        logger.debug.assert_called_with(log_msg)
+        self.bot.stats.incr.assert_called_once_with("tokens.removed_tokens")
+
+        mod_log.ignore.assert_called_once_with(constants.Event.message_delete, self.msg.id)
+        mod_log.send_log_message.assert_called_once_with(
+            icon_url=constants.Icons.token_removed,
+            colour=Colour(constants.Colours.soft_red),
+            title="Token removed!",
+            text=log_msg,
+            thumbnail=self.msg.author.avatar_url_as.return_value,
+            channel_id=constants.Channels.mod_alerts
+        )
+
+
+class TokenRemoverExtensionTests(unittest.TestCase):
+    """Tests for the token_remover extension."""
+
+    @autospec("bot.cogs.token_remover", "TokenRemover")
+    def test_extension_setup(self, cog):
+        """The TokenRemover cog should be added."""
         bot = MockBot()
-        setup_cog(bot)
+        token_remover.setup(bot)
+
+        cog.assert_called_once_with(bot)
         bot.add_cog.assert_called_once()
+        self.assertTrue(isinstance(bot.add_cog.call_args.args[0], TokenRemover))
diff --git a/tests/bot/test_converters.py b/tests/bot/test_converters.py
index ca8cb6825..c42111f3f 100644
--- a/tests/bot/test_converters.py
+++ b/tests/bot/test_converters.py
@@ -1,5 +1,5 @@
-import asyncio
 import datetime
+import re
 import unittest
 from unittest.mock import MagicMock, patch
 
@@ -16,7 +16,7 @@ from bot.converters import (
 )
 
 
-class ConverterTests(unittest.TestCase):
+class ConverterTests(unittest.IsolatedAsyncioTestCase):
     """Tests our custom argument converters."""
 
     @classmethod
@@ -26,7 +26,7 @@ class ConverterTests(unittest.TestCase):
 
         cls.fixed_utc_now = datetime.datetime.fromisoformat('2019-01-01T00:00:00')
 
-    def test_tag_content_converter_for_valid(self):
+    async def test_tag_content_converter_for_valid(self):
         """TagContentConverter should return correct values for valid input."""
         test_values = (
             ('hello', 'hello'),
@@ -35,10 +35,10 @@ class ConverterTests(unittest.TestCase):
 
         for content, expected_conversion in test_values:
             with self.subTest(content=content, expected_conversion=expected_conversion):
-                conversion = asyncio.run(TagContentConverter.convert(self.context, content))
+                conversion = await TagContentConverter.convert(self.context, content)
                 self.assertEqual(conversion, expected_conversion)
 
-    def test_tag_content_converter_for_invalid(self):
+    async def test_tag_content_converter_for_invalid(self):
         """TagContentConverter should raise the proper exception for invalid input."""
         test_values = (
             ('', "Tag contents should not be empty, or filled with whitespace."),
@@ -47,10 +47,10 @@ class ConverterTests(unittest.TestCase):
 
         for value, exception_message in test_values:
             with self.subTest(tag_content=value, exception_message=exception_message):
-                with self.assertRaises(BadArgument, msg=exception_message):
-                    asyncio.run(TagContentConverter.convert(self.context, value))
+                with self.assertRaisesRegex(BadArgument, re.escape(exception_message)):
+                    await TagContentConverter.convert(self.context, value)
 
-    def test_tag_name_converter_for_valid(self):
+    async def test_tag_name_converter_for_valid(self):
         """TagNameConverter should return the correct values for valid tag names."""
         test_values = (
             ('tracebacks', 'tracebacks'),
@@ -60,10 +60,10 @@ class ConverterTests(unittest.TestCase):
 
         for name, expected_conversion in test_values:
             with self.subTest(name=name, expected_conversion=expected_conversion):
-                conversion = asyncio.run(TagNameConverter.convert(self.context, name))
+                conversion = await TagNameConverter.convert(self.context, name)
                 self.assertEqual(conversion, expected_conversion)
 
-    def test_tag_name_converter_for_invalid(self):
+    async def test_tag_name_converter_for_invalid(self):
         """TagNameConverter should raise the correct exception for invalid tag names."""
         test_values = (
             ('👋', "Don't be ridiculous, you can't use that character!"),
@@ -75,29 +75,29 @@ class ConverterTests(unittest.TestCase):
 
         for invalid_name, exception_message in test_values:
             with self.subTest(invalid_name=invalid_name, exception_message=exception_message):
-                with self.assertRaises(BadArgument, msg=exception_message):
-                    asyncio.run(TagNameConverter.convert(self.context, invalid_name))
+                with self.assertRaisesRegex(BadArgument, re.escape(exception_message)):
+                    await TagNameConverter.convert(self.context, invalid_name)
 
-    def test_valid_python_identifier_for_valid(self):
+    async def test_valid_python_identifier_for_valid(self):
         """ValidPythonIdentifier returns valid identifiers unchanged."""
         test_values = ('foo', 'lemon')
 
         for name in test_values:
             with self.subTest(identifier=name):
-                conversion = asyncio.run(ValidPythonIdentifier.convert(self.context, name))
+                conversion = await ValidPythonIdentifier.convert(self.context, name)
                 self.assertEqual(name, conversion)
 
-    def test_valid_python_identifier_for_invalid(self):
+    async def test_valid_python_identifier_for_invalid(self):
         """ValidPythonIdentifier raises the proper exception for invalid identifiers."""
         test_values = ('nested.stuff', '#####')
 
         for name in test_values:
             with self.subTest(identifier=name):
                 exception_message = f'`{name}` is not a valid Python identifier'
-                with self.assertRaises(BadArgument, msg=exception_message):
-                    asyncio.run(ValidPythonIdentifier.convert(self.context, name))
+                with self.assertRaisesRegex(BadArgument, re.escape(exception_message)):
+                    await ValidPythonIdentifier.convert(self.context, name)
 
-    def test_duration_converter_for_valid(self):
+    async def test_duration_converter_for_valid(self):
         """Duration returns the correct `datetime` for valid duration strings."""
         test_values = (
             # Simple duration strings
@@ -159,35 +159,35 @@ class ConverterTests(unittest.TestCase):
                 mock_datetime.utcnow.return_value = self.fixed_utc_now
 
                 with self.subTest(duration=duration, duration_dict=duration_dict):
-                    converted_datetime = asyncio.run(converter.convert(self.context, duration))
+                    converted_datetime = await converter.convert(self.context, duration)
                     self.assertEqual(converted_datetime, expected_datetime)
 
-    def test_duration_converter_for_invalid(self):
+    async def test_duration_converter_for_invalid(self):
         """Duration raises the right exception for invalid duration strings."""
         test_values = (
             # Units in wrong order
-            ('1d1w'),
-            ('1s1y'),
+            '1d1w',
+            '1s1y',
 
             # Duplicated units
-            ('1 year 2 years'),
-            ('1 M 10 minutes'),
+            '1 year 2 years',
+            '1 M 10 minutes',
 
             # Unknown substrings
-            ('1MVes'),
-            ('1y3breads'),
+            '1MVes',
+            '1y3breads',
 
             # Missing amount
-            ('ym'),
+            'ym',
 
             # Incorrect whitespace
-            (" 1y"),
-            ("1S "),
-            ("1y  1m"),
+            " 1y",
+            "1S ",
+            "1y  1m",
 
             # Garbage
-            ('Guido van Rossum'),
-            ('lemon lemon lemon lemon lemon lemon lemon'),
+            'Guido van Rossum',
+            'lemon lemon lemon lemon lemon lemon lemon',
         )
 
         converter = Duration()
@@ -195,10 +195,21 @@ class ConverterTests(unittest.TestCase):
         for invalid_duration in test_values:
             with self.subTest(invalid_duration=invalid_duration):
                 exception_message = f'`{invalid_duration}` is not a valid duration string.'
-                with self.assertRaises(BadArgument, msg=exception_message):
-                    asyncio.run(converter.convert(self.context, invalid_duration))
+                with self.assertRaisesRegex(BadArgument, re.escape(exception_message)):
+                    await converter.convert(self.context, invalid_duration)
 
-    def test_isodatetime_converter_for_valid(self):
+    @patch("bot.converters.datetime")
+    async def test_duration_converter_out_of_range(self, mock_datetime):
+        """Duration converter should raise BadArgument if datetime raises a ValueError."""
+        mock_datetime.__add__.side_effect = ValueError
+        mock_datetime.utcnow.return_value = mock_datetime
+
+        duration = f"{datetime.MAXYEAR}y"
+        exception_message = f"`{duration}` results in a datetime outside the supported range."
+        with self.assertRaisesRegex(BadArgument, re.escape(exception_message)):
+            await Duration().convert(self.context, duration)
+
+    async def test_isodatetime_converter_for_valid(self):
         """ISODateTime converter returns correct datetime for valid datetime string."""
         test_values = (
             # `YYYY-mm-ddTHH:MM:SSZ` | `YYYY-mm-dd HH:MM:SSZ`
@@ -243,37 +254,37 @@ class ConverterTests(unittest.TestCase):
 
         for datetime_string, expected_dt in test_values:
             with self.subTest(datetime_string=datetime_string, expected_dt=expected_dt):
-                converted_dt = asyncio.run(converter.convert(self.context, datetime_string))
+                converted_dt = await converter.convert(self.context, datetime_string)
                 self.assertIsNone(converted_dt.tzinfo)
                 self.assertEqual(converted_dt, expected_dt)
 
-    def test_isodatetime_converter_for_invalid(self):
+    async def test_isodatetime_converter_for_invalid(self):
         """ISODateTime converter raises the correct exception for invalid datetime strings."""
         test_values = (
             # Make sure it doesn't interfere with the Duration converter
-            ('1Y'),
-            ('1d'),
-            ('1H'),
+            '1Y',
+            '1d',
+            '1H',
 
             # Check if it fails when only providing the optional time part
-            ('10:10:10'),
-            ('10:00'),
+            '10:10:10',
+            '10:00',
 
             # Invalid date format
-            ('19-01-01'),
+            '19-01-01',
 
             # Other non-valid strings
-            ('fisk the tag master'),
+            'fisk the tag master',
         )
 
         converter = ISODateTime()
         for datetime_string in test_values:
             with self.subTest(datetime_string=datetime_string):
                 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))
+                with self.assertRaisesRegex(BadArgument, re.escape(exception_message)):
+                    await converter.convert(self.context, datetime_string)
 
-    def test_hush_duration_converter_for_valid(self):
+    async def test_hush_duration_converter_for_valid(self):
         """HushDurationConverter returns correct value for minutes duration or `"forever"` strings."""
         test_values = (
             ("0", 0),
@@ -286,10 +297,10 @@ class ConverterTests(unittest.TestCase):
         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))
+                converted = await converter.convert(self.context, minutes_string)
                 self.assertEqual(expected_minutes, converted)
 
-    def test_hush_duration_converter_for_invalid(self):
+    async 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."),
@@ -299,5 +310,5 @@ class ConverterTests(unittest.TestCase):
         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))
+                with self.assertRaisesRegex(BadArgument, re.escape(exception_message)):
+                    await converter.convert(self.context, invalid_minutes_string)
diff --git a/tests/bot/utils/test_redis_cache.py b/tests/bot/utils/test_redis_cache.py
index 62c411681..a2f0fe55d 100644
--- a/tests/bot/utils/test_redis_cache.py
+++ b/tests/bot/utils/test_redis_cache.py
@@ -44,16 +44,6 @@ class RedisCacheTests(unittest.IsolatedAsyncioTestCase):
         with self.assertRaises(RuntimeError):
             await bad_cache.set("test", "me_up_deadman")
 
-    def test_namespace_collision(self):
-        """Test that we prevent colliding namespaces."""
-        bob_cache_1 = RedisCache()
-        bob_cache_1._set_namespace("BobRoss")
-        self.assertEqual(bob_cache_1._namespace, "BobRoss")
-
-        bob_cache_2 = RedisCache()
-        bob_cache_2._set_namespace("BobRoss")
-        self.assertEqual(bob_cache_2._namespace, "BobRoss_")
-
     async def test_set_get_item(self):
         """Test that users can set and get items from the RedisDict."""
         test_cases = (
diff --git a/tests/helpers.py b/tests/helpers.py
index faa839370..facc4e1af 100644
--- a/tests/helpers.py
+++ b/tests/helpers.py
@@ -5,7 +5,7 @@ import itertools
 import logging
 import unittest.mock
 from asyncio import AbstractEventLoop
-from typing import Iterable, Optional
+from typing import Callable, Iterable, Optional
 
 import discord
 from aiohttp import ClientSession
@@ -26,6 +26,24 @@ for logger in logging.Logger.manager.loggerDict.values():
     logger.setLevel(logging.CRITICAL)
 
 
+def autospec(target, *attributes: str, **kwargs) -> Callable:
+    """Patch multiple `attributes` of a `target` with autospecced mocks and `spec_set` as True."""
+    # Caller's kwargs should take priority and overwrite the defaults.
+    kwargs = {'spec_set': True, 'autospec': True, **kwargs}
+
+    # Import the target if it's a string.
+    # This is to support both object and string targets like patch.multiple.
+    if type(target) is str:
+        target = unittest.mock._importer(target)
+
+    def decorator(func):
+        for attribute in attributes:
+            patcher = unittest.mock.patch.object(target, attribute, **kwargs)
+            func = patcher(func)
+        return func
+    return decorator
+
+
 class HashableMixin(discord.mixins.EqualityComparable):
     """
     Mixin that provides similar hashing and equality functionality as discord.py's `Hashable` mixin.