Merge branch 'master' into remove_periodic_ping

14 files changed, 354 insertions, 63 deletions

diff --git a/bot/cogs/antimalware.py b/bot/cogs/antimalware.py
index 66b5073e8..ea257442e 100644
--- a/bot/cogs/antimalware.py
+++ b/bot/cogs/antimalware.py
@@ -1,4 +1,5 @@
 import logging
+import typing as t
 from os.path import splitext
 
 from discord import Embed, Message, NotFound
@@ -9,6 +10,27 @@ from bot.constants import AntiMalware as AntiMalwareConfig, Channels, STAFF_ROLE
 
 log = logging.getLogger(__name__)
 
+PY_EMBED_DESCRIPTION = (
+    "It looks like you tried to attach a Python file - "
+    f"please use a code-pasting service such as {URLs.site_schema}{URLs.site_paste}"
+)
+
+TXT_EMBED_DESCRIPTION = (
+    "**Uh-oh!** It looks like your message got zapped by our spam filter. "
+    "We currently don't allow `.txt` attachments, so here are some tips to help you travel safely: \n\n"
+    "• If you attempted to send a message longer than 2000 characters, try shortening your message "
+    "to fit within the character limit or use a pasting service (see below) \n\n"
+    "• If you tried to show someone your code, you can use codeblocks \n(run `!code-blocks` in "
+    "{cmd_channel_mention} for more information) or use a pasting service like: "
+    f"\n\n{URLs.site_schema}{URLs.site_paste}"
+)
+
+DISALLOWED_EMBED_DESCRIPTION = (
+    "It looks like you tried to attach file type(s) that we do not allow ({blocked_extensions_str}). "
+    f"We currently allow the following file types: **{', '.join(AntiMalwareConfig.whitelist)}**.\n\n"
+    "Feel free to ask in {meta_channel_mention} if you think this is a mistake."
+)
+
 
 class AntiMalware(Cog):
     """Delete messages which contain attachments with non-whitelisted file extensions."""
@@ -29,34 +51,20 @@ class AntiMalware(Cog):
             return
 
         embed = Embed()
-        file_extensions = {splitext(attachment.filename.lower())[1] for attachment in message.attachments}
-        extensions_blocked = file_extensions - set(AntiMalwareConfig.whitelist)
+        extensions_blocked = self.get_disallowed_extensions(message)
         blocked_extensions_str = ', '.join(extensions_blocked)
         if ".py" in extensions_blocked:
             # Short-circuit on *.py files to provide a pastebin link
-            embed.description = (
-                "It looks like you tried to attach a Python file - "
-                f"please use a code-pasting service such as {URLs.site_schema}{URLs.site_paste}"
-            )
+            embed.description = PY_EMBED_DESCRIPTION
         elif ".txt" in extensions_blocked:
             # Work around Discord AutoConversion of messages longer than 2000 chars to .txt
             cmd_channel = self.bot.get_channel(Channels.bot_commands)
-            embed.description = (
-                "**Uh-oh!** It looks like your message got zapped by our spam filter. "
-                "We currently don't allow `.txt` attachments, so here are some tips to help you travel safely: \n\n"
-                "• If you attempted to send a message longer than 2000 characters, try shortening your message "
-                "to fit within the character limit or use a pasting service (see below) \n\n"
-                "• If you tried to show someone your code, you can use codeblocks \n(run `!code-blocks` in "
-                f"{cmd_channel.mention} for more information) or use a pasting service like: "
-                f"\n\n{URLs.site_schema}{URLs.site_paste}"
-            )
+            embed.description = TXT_EMBED_DESCRIPTION.format(cmd_channel_mention=cmd_channel.mention)
         elif extensions_blocked:
-            whitelisted_types = ', '.join(AntiMalwareConfig.whitelist)
             meta_channel = self.bot.get_channel(Channels.meta)
-            embed.description = (
-                f"It looks like you tried to attach file type(s) that we do not allow ({blocked_extensions_str}). "
-                f"We currently allow the following file types: **{whitelisted_types}**.\n\n"
-                f"Feel free to ask in {meta_channel.mention} if you think this is a mistake."
+            embed.description = DISALLOWED_EMBED_DESCRIPTION.format(
+                blocked_extensions_str=blocked_extensions_str,
+                meta_channel_mention=meta_channel.mention,
             )
 
         if embed.description:
@@ -73,6 +81,13 @@ class AntiMalware(Cog):
             except NotFound:
                 log.info(f"Tried to delete message `{message.id}`, but message could not be found.")
 
+    @classmethod
+    def get_disallowed_extensions(cls, message: Message) -> t.Iterable[str]:
+        """Get an iterable containing all the disallowed extensions of attachments."""
+        file_extensions = {splitext(attachment.filename.lower())[1] for attachment in message.attachments}
+        extensions_blocked = file_extensions - set(AntiMalwareConfig.whitelist)
+        return extensions_blocked
+
 
 def setup(bot: Bot) -> None:
     """Load the AntiMalware cog."""
diff --git a/bot/cogs/moderation/infractions.py b/bot/cogs/moderation/infractions.py
index e62a36c43..5bfaad796 100644
--- a/bot/cogs/moderation/infractions.py
+++ b/bot/cogs/moderation/infractions.py
@@ -1,4 +1,5 @@
 import logging
+import textwrap
 import typing as t
 
 import discord
@@ -225,7 +226,7 @@ class Infractions(InfractionScheduler, commands.Cog):
 
         self.mod_log.ignore(Event.member_remove, user.id)
 
-        action = user.kick(reason=reason)
+        action = user.kick(reason=textwrap.shorten(reason, width=512, placeholder="..."))
         await self.apply_infraction(ctx, infraction, user, action)
 
     @respect_role_hierarchy()
@@ -258,7 +259,9 @@ class Infractions(InfractionScheduler, commands.Cog):
 
         self.mod_log.ignore(Event.member_remove, user.id)
 
-        action = ctx.guild.ban(user, reason=reason, delete_message_days=0)
+        truncated_reason = textwrap.shorten(reason, width=512, placeholder="...")
+
+        action = ctx.guild.ban(user, reason=truncated_reason, delete_message_days=0)
         await self.apply_infraction(ctx, infraction, user, action)
 
         if infraction.get('expires_at') is not None:
diff --git a/bot/cogs/moderation/modlog.py b/bot/cogs/moderation/modlog.py
index beef7a8ef..9d28030d9 100644
--- a/bot/cogs/moderation/modlog.py
+++ b/bot/cogs/moderation/modlog.py
@@ -98,7 +98,10 @@ class ModLog(Cog, name="ModLog"):
         footer: t.Optional[str] = None,
     ) -> Context:
         """Generate log embed and send to logging channel."""
-        embed = discord.Embed(description=text)
+        # Truncate string directly here to avoid removing newlines
+        embed = discord.Embed(
+            description=text[:2045] + "..." if len(text) > 2048 else text
+        )
 
         if title and icon_url:
             embed.set_author(name=title, icon_url=icon_url)
diff --git a/bot/cogs/moderation/scheduler.py b/bot/cogs/moderation/scheduler.py
index 012432e60..f0a3ad1b1 100644
--- a/bot/cogs/moderation/scheduler.py
+++ b/bot/cogs/moderation/scheduler.py
@@ -101,33 +101,17 @@ class InfractionScheduler(Scheduler):
 
         dm_result = ""
         dm_log_text = ""
-        expiry_log_text = f"Expires: {expiry}" if expiry else ""
+        expiry_log_text = f"\nExpires: {expiry}" if expiry else ""
         log_title = "applied"
         log_content = None
-
-        # DM the user about the infraction if it's not a shadow/hidden infraction.
-        if not infraction["hidden"]:
-            dm_result = f"{constants.Emojis.failmail} "
-            dm_log_text = "\nDM: **Failed**"
-
-            # Sometimes user is a discord.Object; make it a proper user.
-            try:
-                if not isinstance(user, (discord.Member, discord.User)):
-                    user = await self.bot.fetch_user(user.id)
-            except discord.HTTPException as e:
-                log.error(f"Failed to DM {user.id}: could not fetch user (status {e.status})")
-            else:
-                # Accordingly display whether the user was successfully notified via DM.
-                if await utils.notify_infraction(user, infr_type, expiry, reason, icon):
-                    dm_result = ":incoming_envelope: "
-                    dm_log_text = "\nDM: Sent"
+        failed = False
 
         if infraction["actor"] == self.bot.user.id:
             log.trace(
                 f"Infraction #{id_} actor is bot; including the reason in the confirmation message."
             )
 
-            end_msg = f" (reason: {infraction['reason']})"
+            end_msg = f" (reason: {textwrap.shorten(reason, width=1500, placeholder='...')})"
         elif ctx.channel.id not in STAFF_CHANNELS:
             log.trace(
                 f"Infraction #{id_} context is not in a staff channel; omitting infraction count."
@@ -164,12 +148,43 @@ class InfractionScheduler(Scheduler):
                     log.warning(f"{log_msg}: bot lacks permissions.")
                 else:
                     log.exception(log_msg)
+                failed = True
+
+        # DM the user about the infraction if it's not a shadow/hidden infraction.
+        # Don't send DM when applying failed.
+        if not infraction["hidden"] and not failed:
+            dm_result = f"{constants.Emojis.failmail} "
+            dm_log_text = "\nDM: **Failed**"
+
+            # Sometimes user is a discord.Object; make it a proper user.
+            try:
+                if not isinstance(user, (discord.Member, discord.User)):
+                    user = await self.bot.fetch_user(user.id)
+            except discord.HTTPException as e:
+                log.error(f"Failed to DM {user.id}: could not fetch user (status {e.status})")
+            else:
+                # Accordingly display whether the user was successfully notified via DM.
+                if await utils.notify_infraction(user, infr_type, expiry, reason, icon):
+                    dm_result = ":incoming_envelope: "
+                    dm_log_text = "\nDM: Sent"
+
+        if failed:
+            dm_log_text = "\nDM: **Canceled**"
+            dm_result = f"{constants.Emojis.failmail} "
+            log.trace(f"Deleted infraction {infraction['id']} from database because applying infraction failed.")
+            try:
+                await self.bot.api_client.delete(f"bot/infractions/{id_}")
+            except ResponseCodeError as e:
+                confirm_msg += " and failed to delete"
+                log_title += " and failed to delete"
+                log.error(f"Deletion of {infr_type} infraction #{id_} failed with error code {e.status}.")
+            infr_message = ""
+        else:
+            infr_message = f" **{infr_type}** to {user.mention}{expiry_msg}{end_msg}"
 
         # Send a confirmation message to the invoking context.
         log.trace(f"Sending infraction #{id_} confirmation message.")
-        await ctx.send(
-            f"{dm_result}{confirm_msg} **{infr_type}** to {user.mention}{expiry_msg}{end_msg}."
-        )
+        await ctx.send(f"{dm_result}{confirm_msg}{infr_message}.")
 
         # Send a log message to the mod log.
         log.trace(f"Sending apply mod log for infraction #{id_}.")
@@ -180,9 +195,8 @@ class InfractionScheduler(Scheduler):
             thumbnail=user.avatar_url_as(static_format="png"),
             text=textwrap.dedent(f"""
                 Member: {user.mention} (`{user.id}`)
-                Actor: {ctx.message.author}{dm_log_text}
+                Actor: {ctx.message.author}{dm_log_text}{expiry_log_text}
                 Reason: {reason}
-                {expiry_log_text}
             """),
             content=log_content,
             footer=f"ID {infraction['id']}"
@@ -294,6 +308,9 @@ class InfractionScheduler(Scheduler):
                 f"{log_text.get('Failure', '')}"
             )
 
+        # Move reason to end of entry to avoid cutting out some keys
+        log_text["Reason"] = log_text.pop("Reason")
+
         # Send a log message to the mod log.
         await self.mod_log.send_log_message(
             icon_url=utils.INFRACTION_ICONS[infr_type][1],
@@ -407,6 +424,9 @@ class InfractionScheduler(Scheduler):
             user = self.bot.get_user(user_id)
             avatar = user.avatar_url_as(static_format="png") if user else None
 
+            # Move reason to end so when reason is too long, this is not gonna cut out required items.
+            log_text["Reason"] = log_text.pop("Reason")
+
             log.trace(f"Sending deactivation mod log for infraction #{id_}.")
             await self.mod_log.send_log_message(
                 icon_url=utils.INFRACTION_ICONS[type_][1],
@@ -416,7 +436,6 @@ class InfractionScheduler(Scheduler):
                 text="\n".join(f"{k}: {v}" for k, v in log_text.items()),
                 footer=f"ID: {id_}",
                 content=log_content,
-
             )
 
         return log_text
diff --git a/bot/cogs/moderation/superstarify.py b/bot/cogs/moderation/superstarify.py
index 29855c325..45a010f00 100644
--- a/bot/cogs/moderation/superstarify.py
+++ b/bot/cogs/moderation/superstarify.py
@@ -183,10 +183,10 @@ class Superstarify(InfractionScheduler, Cog):
             text=textwrap.dedent(f"""
                 Member: {member.mention} (`{member.id}`)
                 Actor: {ctx.message.author}
-                Reason: {reason}
                 Expires: {expiry_str}
                 Old nickname: `{old_nick}`
                 New nickname: `{forced_nick}`
+                Reason: {reason}
             """),
             footer=f"ID {id_}"
         )
diff --git a/bot/cogs/moderation/utils.py b/bot/cogs/moderation/utils.py
index e4e0f1ec2..1b716b2ea 100644
--- a/bot/cogs/moderation/utils.py
+++ b/bot/cogs/moderation/utils.py
@@ -143,12 +143,14 @@ async def notify_infraction(
     """DM a user about their new infraction and return True if the DM is successful."""
     log.trace(f"Sending {user} a DM about their {infr_type} infraction.")
 
+    text = textwrap.dedent(f"""
+        **Type:** {infr_type.capitalize()}
+        **Expires:** {expires_at or "N/A"}
+        **Reason:** {reason or "No reason provided."}
+    """)
+
     embed = discord.Embed(
-        description=textwrap.dedent(f"""
-            **Type:** {infr_type.capitalize()}
-            **Expires:** {expires_at or "N/A"}
-            **Reason:** {reason or "No reason provided."}
-            """),
+        description=textwrap.shorten(text, width=2048, placeholder="..."),
         colour=Colours.soft_red
     )
 
diff --git a/bot/cogs/tags.py b/bot/cogs/tags.py
index bc7f53f68..6f03a3475 100644
--- a/bot/cogs/tags.py
+++ b/bot/cogs/tags.py
@@ -44,7 +44,7 @@ class Tags(Cog):
                 tag = {
                     "title": tag_title,
                     "embed": {
-                        "description": file.read_text(),
+                        "description": file.read_text(encoding="utf8"),
                     },
                     "restricted_to": "developers",
                 }
diff --git a/bot/cogs/watchchannels/bigbrother.py b/bot/cogs/watchchannels/bigbrother.py
index e4fb173e0..702d371f4 100644
--- a/bot/cogs/watchchannels/bigbrother.py
+++ b/bot/cogs/watchchannels/bigbrother.py
@@ -1,4 +1,5 @@
 import logging
+import textwrap
 from collections import ChainMap
 
 from discord.ext.commands import Cog, Context, group
@@ -97,8 +98,8 @@ class BigBrother(WatchChannel, Cog, name="Big Brother"):
 
             if len(history) > 1:
                 total = f"({len(history) // 2} previous infractions in total)"
-                end_reason = history[0]["reason"]
-                start_reason = f"Watched: {history[1]['reason']}"
+                end_reason = textwrap.shorten(history[0]["reason"], width=500, placeholder="...")
+                start_reason = f"Watched: {textwrap.shorten(history[1]['reason'], width=500, placeholder='...')}"
                 msg += f"\n\nUser's previous watch reasons {total}:```{start_reason}\n\n{end_reason}```"
         else:
             msg = ":x: Failed to post the infraction: response was empty."
diff --git a/bot/cogs/watchchannels/talentpool.py b/bot/cogs/watchchannels/talentpool.py
index cd9c7e555..14547105f 100644
--- a/bot/cogs/watchchannels/talentpool.py
+++ b/bot/cogs/watchchannels/talentpool.py
@@ -106,8 +106,8 @@ class TalentPool(WatchChannel, Cog, name="Talentpool"):
 
         if history:
             total = f"({len(history)} previous nominations in total)"
-            start_reason = f"Watched: {history[0]['reason']}"
-            end_reason = f"Unwatched: {history[0]['end_reason']}"
+            start_reason = f"Watched: {textwrap.shorten(history[0]['reason'], width=500, placeholder='...')}"
+            end_reason = f"Unwatched: {textwrap.shorten(history[0]['end_reason'], width=500, placeholder='...')}"
             msg += f"\n\nUser's previous watch reasons {total}:```{start_reason}\n\n{end_reason}```"
 
         await ctx.send(msg)
@@ -224,7 +224,7 @@ class TalentPool(WatchChannel, Cog, name="Talentpool"):
                 Status: **Active**
                 Date: {start_date}
                 Actor: {actor.mention if actor else actor_id}
-                Reason: {nomination_object["reason"]}
+                Reason: {textwrap.shorten(nomination_object["reason"], width=200, placeholder="...")}
                 Nomination ID: `{nomination_object["id"]}`
                 ===============
                 """
@@ -237,10 +237,10 @@ class TalentPool(WatchChannel, Cog, name="Talentpool"):
                 Status: Inactive
                 Date: {start_date}
                 Actor: {actor.mention if actor else actor_id}
-                Reason: {nomination_object["reason"]}
+                Reason: {textwrap.shorten(nomination_object["reason"], width=200, placeholder="...")}
 
                 End date: {end_date}
-                Unwatch reason: {nomination_object["end_reason"]}
+                Unwatch reason: {textwrap.shorten(nomination_object["end_reason"], width=200, placeholder="...")}
                 Nomination ID: `{nomination_object["id"]}`
                 ===============
                 """
diff --git a/bot/cogs/watchchannels/watchchannel.py b/bot/cogs/watchchannels/watchchannel.py
index 643cd46e4..436778c46 100644
--- a/bot/cogs/watchchannels/watchchannel.py
+++ b/bot/cogs/watchchannels/watchchannel.py
@@ -280,8 +280,9 @@ class WatchChannel(metaclass=CogABCMeta):
         else:
             message_jump = f"in [#{msg.channel.name}]({msg.jump_url})"
 
+        footer = f"Added {time_delta} by {actor} | Reason: {reason}"
         embed = Embed(description=f"{msg.author.mention} {message_jump}")
-        embed.set_footer(text=f"Added {time_delta} by {actor} | Reason: {reason}")
+        embed.set_footer(text=textwrap.shorten(footer, width=128, placeholder="..."))
 
         await self.webhook_send(embed=embed, username=msg.author.display_name, avatar_url=msg.author.avatar_url)
 
diff --git a/tests/bot/cogs/moderation/test_infractions.py b/tests/bot/cogs/moderation/test_infractions.py
new file mode 100644
index 000000000..da4e92ccc
--- /dev/null
+++ b/tests/bot/cogs/moderation/test_infractions.py
@@ -0,0 +1,55 @@
+import textwrap
+import unittest
+from unittest.mock import AsyncMock, Mock, patch
+
+from bot.cogs.moderation.infractions import Infractions
+from tests.helpers import MockBot, MockContext, MockGuild, MockMember, MockRole
+
+
+class TruncationTests(unittest.IsolatedAsyncioTestCase):
+    """Tests for ban and kick command reason truncation."""
+
+    def setUp(self):
+        self.bot = MockBot()
+        self.cog = Infractions(self.bot)
+        self.user = MockMember(id=1234, top_role=MockRole(id=3577, position=10))
+        self.target = MockMember(id=1265, top_role=MockRole(id=9876, position=0))
+        self.guild = MockGuild(id=4567)
+        self.ctx = MockContext(bot=self.bot, author=self.user, guild=self.guild)
+
+    @patch("bot.cogs.moderation.utils.get_active_infraction")
+    @patch("bot.cogs.moderation.utils.post_infraction")
+    async def test_apply_ban_reason_truncation(self, post_infraction_mock, get_active_mock):
+        """Should truncate reason for `ctx.guild.ban`."""
+        get_active_mock.return_value = None
+        post_infraction_mock.return_value = {"foo": "bar"}
+
+        self.cog.apply_infraction = AsyncMock()
+        self.bot.get_cog.return_value = AsyncMock()
+        self.cog.mod_log.ignore = Mock()
+        self.ctx.guild.ban = Mock()
+
+        await self.cog.apply_ban(self.ctx, self.target, "foo bar" * 3000)
+        self.ctx.guild.ban.assert_called_once_with(
+            self.target,
+            reason=textwrap.shorten("foo bar" * 3000, 512, placeholder="..."),
+            delete_message_days=0
+        )
+        self.cog.apply_infraction.assert_awaited_once_with(
+            self.ctx, {"foo": "bar"}, self.target, self.ctx.guild.ban.return_value
+        )
+
+    @patch("bot.cogs.moderation.utils.post_infraction")
+    async def test_apply_kick_reason_truncation(self, post_infraction_mock):
+        """Should truncate reason for `Member.kick`."""
+        post_infraction_mock.return_value = {"foo": "bar"}
+
+        self.cog.apply_infraction = AsyncMock()
+        self.cog.mod_log.ignore = Mock()
+        self.target.kick = Mock()
+
+        await self.cog.apply_kick(self.ctx, self.target, "foo bar" * 3000)
+        self.target.kick.assert_called_once_with(reason=textwrap.shorten("foo bar" * 3000, 512, placeholder="..."))
+        self.cog.apply_infraction.assert_awaited_once_with(
+            self.ctx, {"foo": "bar"}, self.target, self.target.kick.return_value
+        )
diff --git a/tests/bot/cogs/moderation/test_modlog.py b/tests/bot/cogs/moderation/test_modlog.py
new file mode 100644
index 000000000..f2809f40a
--- /dev/null
+++ b/tests/bot/cogs/moderation/test_modlog.py
@@ -0,0 +1,29 @@
+import unittest
+
+import discord
+
+from bot.cogs.moderation.modlog import ModLog
+from tests.helpers import MockBot, MockTextChannel
+
+
+class ModLogTests(unittest.IsolatedAsyncioTestCase):
+    """Tests for moderation logs."""
+
+    def setUp(self):
+        self.bot = MockBot()
+        self.cog = ModLog(self.bot)
+        self.channel = MockTextChannel()
+
+    async def test_log_entry_description_truncation(self):
+        """Test that embed description for ModLog entry is truncated."""
+        self.bot.get_channel.return_value = self.channel
+        await self.cog.send_log_message(
+            icon_url="foo",
+            colour=discord.Colour.blue(),
+            title="bar",
+            text="foo bar" * 3000
+        )
+        embed = self.channel.send.call_args[1]["embed"]
+        self.assertEqual(
+            embed.description, ("foo bar" * 3000)[:2045] + "..."
+        )
diff --git a/tests/bot/cogs/test_antimalware.py b/tests/bot/cogs/test_antimalware.py
new file mode 100644
index 000000000..f219fc1ba
--- /dev/null
+++ b/tests/bot/cogs/test_antimalware.py
@@ -0,0 +1,159 @@
+import unittest
+from unittest.mock import AsyncMock, Mock, patch
+
+from discord import NotFound
+
+from bot.cogs import antimalware
+from bot.constants import AntiMalware as AntiMalwareConfig, Channels, STAFF_ROLES
+from tests.helpers import MockAttachment, MockBot, MockMessage, MockRole
+
+MODULE = "bot.cogs.antimalware"
+
+
+@patch(f"{MODULE}.AntiMalwareConfig.whitelist", new=[".first", ".second", ".third"])
+class AntiMalwareCogTests(unittest.IsolatedAsyncioTestCase):
+    """Test the AntiMalware cog."""
+
+    def setUp(self):
+        """Sets up fresh objects for each test."""
+        self.bot = MockBot()
+        self.cog = antimalware.AntiMalware(self.bot)
+        self.message = MockMessage()
+
+    async def test_message_with_allowed_attachment(self):
+        """Messages with allowed extensions should not be deleted"""
+        attachment = MockAttachment(filename=f"python{AntiMalwareConfig.whitelist[0]}")
+        self.message.attachments = [attachment]
+
+        await self.cog.on_message(self.message)
+        self.message.delete.assert_not_called()
+
+    async def test_message_without_attachment(self):
+        """Messages without attachments should result in no action."""
+        await self.cog.on_message(self.message)
+        self.message.delete.assert_not_called()
+
+    async def test_direct_message_with_attachment(self):
+        """Direct messages should have no action taken."""
+        attachment = MockAttachment(filename="python.disallowed")
+        self.message.attachments = [attachment]
+        self.message.guild = None
+
+        await self.cog.on_message(self.message)
+
+        self.message.delete.assert_not_called()
+
+    async def test_message_with_illegal_extension_gets_deleted(self):
+        """A message containing an illegal extension should send an embed."""
+        attachment = MockAttachment(filename="python.disallowed")
+        self.message.attachments = [attachment]
+
+        await self.cog.on_message(self.message)
+
+        self.message.delete.assert_called_once()
+
+    async def test_message_send_by_staff(self):
+        """A message send by a member of staff should be ignored."""
+        staff_role = MockRole(id=STAFF_ROLES[0])
+        self.message.author.roles.append(staff_role)
+        attachment = MockAttachment(filename="python.disallowed")
+        self.message.attachments = [attachment]
+
+        await self.cog.on_message(self.message)
+
+        self.message.delete.assert_not_called()
+
+    async def test_python_file_redirect_embed_description(self):
+        """A message containing a .py file should result in an embed redirecting the user to our paste site"""
+        attachment = MockAttachment(filename="python.py")
+        self.message.attachments = [attachment]
+        self.message.channel.send = AsyncMock()
+
+        await self.cog.on_message(self.message)
+        self.message.channel.send.assert_called_once()
+        args, kwargs = self.message.channel.send.call_args
+        embed = kwargs.pop("embed")
+
+        self.assertEqual(embed.description, antimalware.PY_EMBED_DESCRIPTION)
+
+    async def test_txt_file_redirect_embed_description(self):
+        """A message containing a .txt file should result in the correct embed."""
+        attachment = MockAttachment(filename="python.txt")
+        self.message.attachments = [attachment]
+        self.message.channel.send = AsyncMock()
+        antimalware.TXT_EMBED_DESCRIPTION = Mock()
+        antimalware.TXT_EMBED_DESCRIPTION.format.return_value = "test"
+
+        await self.cog.on_message(self.message)
+        self.message.channel.send.assert_called_once()
+        args, kwargs = self.message.channel.send.call_args
+        embed = kwargs.pop("embed")
+        cmd_channel = self.bot.get_channel(Channels.bot_commands)
+
+        self.assertEqual(embed.description, antimalware.TXT_EMBED_DESCRIPTION.format.return_value)
+        antimalware.TXT_EMBED_DESCRIPTION.format.assert_called_with(cmd_channel_mention=cmd_channel.mention)
+
+    async def test_other_disallowed_extention_embed_description(self):
+        """Test the description for a non .py/.txt disallowed extension."""
+        attachment = MockAttachment(filename="python.disallowed")
+        self.message.attachments = [attachment]
+        self.message.channel.send = AsyncMock()
+        antimalware.DISALLOWED_EMBED_DESCRIPTION = Mock()
+        antimalware.DISALLOWED_EMBED_DESCRIPTION.format.return_value = "test"
+
+        await self.cog.on_message(self.message)
+        self.message.channel.send.assert_called_once()
+        args, kwargs = self.message.channel.send.call_args
+        embed = kwargs.pop("embed")
+        meta_channel = self.bot.get_channel(Channels.meta)
+
+        self.assertEqual(embed.description, antimalware.DISALLOWED_EMBED_DESCRIPTION.format.return_value)
+        antimalware.DISALLOWED_EMBED_DESCRIPTION.format.assert_called_with(
+            blocked_extensions_str=".disallowed",
+            meta_channel_mention=meta_channel.mention
+        )
+
+    async def test_removing_deleted_message_logs(self):
+        """Removing an already deleted message logs the correct message"""
+        attachment = MockAttachment(filename="python.disallowed")
+        self.message.attachments = [attachment]
+        self.message.delete = AsyncMock(side_effect=NotFound(response=Mock(status=""), message=""))
+
+        with self.assertLogs(logger=antimalware.log, level="INFO"):
+            await self.cog.on_message(self.message)
+        self.message.delete.assert_called_once()
+
+    async def test_message_with_illegal_attachment_logs(self):
+        """Deleting a message with an illegal attachment should result in a log."""
+        attachment = MockAttachment(filename="python.disallowed")
+        self.message.attachments = [attachment]
+
+        with self.assertLogs(logger=antimalware.log, level="INFO"):
+            await self.cog.on_message(self.message)
+
+    async def test_get_disallowed_extensions(self):
+        """The return value should include all non-whitelisted extensions."""
+        test_values = (
+            ([], []),
+            (AntiMalwareConfig.whitelist, []),
+            ([".first"], []),
+            ([".first", ".disallowed"], [".disallowed"]),
+            ([".disallowed"], [".disallowed"]),
+            ([".disallowed", ".illegal"], [".disallowed", ".illegal"]),
+        )
+
+        for extensions, expected_disallowed_extensions in test_values:
+            with self.subTest(extensions=extensions, expected_disallowed_extensions=expected_disallowed_extensions):
+                self.message.attachments = [MockAttachment(filename=f"filename{extension}") for extension in extensions]
+                disallowed_extensions = self.cog.get_disallowed_extensions(self.message)
+                self.assertCountEqual(disallowed_extensions, expected_disallowed_extensions)
+
+
+class AntiMalwareSetupTests(unittest.TestCase):
+    """Tests setup of the `AntiMalware` cog."""
+
+    def test_setup(self):
+        """Setup of the extension should call add_cog."""
+        bot = MockBot()
+        antimalware.setup(bot)
+        bot.add_cog.assert_called_once()
diff --git a/tests/helpers.py b/tests/helpers.py
index 13283339b..faa839370 100644
--- a/tests/helpers.py
+++ b/tests/helpers.py
@@ -208,6 +208,10 @@ class MockRole(CustomMockMixin, unittest.mock.Mock, ColourMixin, HashableMixin):
         """Simplified position-based comparisons similar to those of `discord.Role`."""
         return self.position < other.position
 
+    def __ge__(self, other):
+        """Simplified position-based comparisons similar to those of `discord.Role`."""
+        return self.position >= other.position
+
 
 # Create a Member instance to get a realistic Mock of `discord.Member`
 member_data = {'user': 'lemon', 'roles': [1]}