diff --git a/.gitignore b/.gitignore
index 0330071..f106780 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,4 @@
 venv
+__pycache__
 .env
+.coverage
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
new file mode 100644
index 0000000..e86df46
--- /dev/null
+++ b/.gitlab-ci.yml
@@ -0,0 +1,32 @@
+stages:
+  - test-lint-format
+
+.job_setup:
+  image: python:3.9
+  before_script:
+    - pip install -r requirements.txt
+
+pylint:
+  extends:
+    - .job_setup
+  stage: test-lint-format
+  script:
+    - pylint src/ test/
+
+autopep8:
+  extends:
+    - .job_setup
+  stage: test-lint-format
+  script:
+    - autopep8 --recursive --diff src/ test/
+
+pytest:
+  extends:
+    - .job_setup
+  stage: test-lint-format
+  script:
+    - pytest --cov=src/
+    - coverage xml
+  artifacts:
+    reports:
+      cobertura: coverage.xml
diff --git a/.pylintrc b/.pylintrc
new file mode 100644
index 0000000..6df1145
--- /dev/null
+++ b/.pylintrc
@@ -0,0 +1,22 @@
+[MASTER]
+init-hook="from pylint.config import find_pylintrc; import os, sys; sys.path.append(os.path.dirname(find_pylintrc()) + '/src'); sys.path.append(os.path.dirname(find_pylintrc()) + '/test')"
+
+[MESSAGES CONTROL]
+disable=
+  missing-module-docstring,
+  missing-class-docstring,
+  missing-function-docstring,
+  global-statement,
+  too-many-arguments,
+  too-few-public-methods,
+  wrong-import-position,
+  redefined-outer-name,
+  invalid-name,
+  no-self-use
+
+[FORMAT]
+indent-string='  '
+max-line-length=160
+
+[SIMILARITIES]
+ignore-comments = no
\ No newline at end of file
diff --git a/.vscode/extensions.json b/.vscode/extensions.json
new file mode 100644
index 0000000..eea6cb0
--- /dev/null
+++ b/.vscode/extensions.json
@@ -0,0 +1,3 @@
+{
+  "recommendations": ["littlefoxteam.vscode-python-test-adapter"]
+}
diff --git a/.vscode/launch.json b/.vscode/launch.json
new file mode 100644
index 0000000..b6a65fa
--- /dev/null
+++ b/.vscode/launch.json
@@ -0,0 +1,14 @@
+{
+  // Use IntelliSense to learn about possible attributes.
+  // Hover to view descriptions of existing attributes.
+  // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+  "version": "0.2.0",
+  "configurations": [
+    {
+      "name": "pytest",
+      "type": "python",
+      "request": "launch",
+      "module": "pytest"
+    }
+  ]
+}
diff --git a/.vscode/settings.json b/.vscode/settings.json
new file mode 100644
index 0000000..e52f158
--- /dev/null
+++ b/.vscode/settings.json
@@ -0,0 +1,5 @@
+{
+  "python.pythonPath": "venv/bin/python3.9",
+  "python.testing.autoTestDiscoverOnSaveEnabled": true,
+  "pythonTestExplorer.testFramework": "pytest"
+}
diff --git a/requirements.txt b/requirements.txt
index db3ff52..04e10c6 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,19 +1,35 @@
 aiohttp==3.7.4.post0
+astroid==2.8.0
 async-timeout==3.0.1
 attrs==21.2.0
 autopep8==1.5.7
 cffi==1.14.6
 chardet==4.0.0
+coverage==5.5
 discord==1.7.3
 discord.py==1.7.3
 idna==3.2
+iniconfig==1.1.1
+isort==5.9.3
+lazy-object-proxy==1.6.0
+mccabe==0.6.1
 multidict==5.1.0
+packaging==21.0
+platformdirs==2.3.0
+pluggy==1.0.0
+py==1.10.0
 pycodestyle==2.7.0
 pycparser==2.20
+pylint==2.11.1
 PyNaCl==1.4.0
+pyparsing==2.4.7
+pytest==6.2.5
+pytest-cov==2.12.1
+pytest-mock==3.6.1
 python-dotenv==0.19.0
 six==1.16.0
 toml==0.10.2
 typing-extensions==3.10.0.2
+wrapt==1.12.1
 yarl==1.6.3
 youtube-dl==2021.6.6
diff --git a/src/bot.py b/src/bot.py
index eddb57c..9964019 100644
--- a/src/bot.py
+++ b/src/bot.py
@@ -1,11 +1,11 @@
-import asyncio
 import os
+import sys
 
-import discord
 from discord.ext import commands
 from dotenv import load_dotenv
 
 from yt import YTDLSource
+from error import ErrorHandler
 
 load_dotenv()
 
@@ -14,88 +14,43 @@ class Music(commands.Cog):
   def __init__(self, bot):
     self.bot = bot
 
-  @commands.command()
-  async def join(self, ctx, *, channel: discord.VoiceChannel):
-    """Joins a voice channel"""
-
-    if ctx.voice_client is not None:
-      return await ctx.voice_client.move_to(channel)
-
-    await channel.connect()
-
-  @commands.command()
-  async def play(self, ctx, *, query):
-    """Plays a file from the local filesystem"""
-
-    source = discord.PCMVolumeTransformer(discord.FFmpegPCMAudio(query))
-    ctx.voice_client.play(source, after=lambda e: print('Player error: %s' % e) if e else None)
-
-    await ctx.send('Now playing: {}'.format(query))
-
-  @commands.command()
-  async def yt(self, ctx, *, url):
-    """Plays from a url (almost anything youtube_dl supports)"""
-
-    async with ctx.typing():
-      player = await YTDLSource.from_url(url, loop=self.bot.loop)
-      ctx.voice_client.play(player, after=lambda e: print('Player error: %s' % e) if e else None)
-
-    await ctx.send('Now playing: {}'.format(player.title))
-
   @commands.command()
   async def stream(self, ctx, *, url):
-    """Streams from a url (same as yt, but doesn't predownload)"""
-
     async with ctx.typing():
       player = await YTDLSource.from_url(url, loop=self.bot.loop, stream=True)
-      ctx.voice_client.play(player, after=lambda e: print('Player error: %s' % e) if e else None)
+      ctx.voice_client.play(player, after=lambda e: print(f"Player error: {e}") if e else None)
 
-    await ctx.send('Now playing: {}'.format(player.title))
-
-  @commands.command()
-  async def volume(self, ctx, volume: int):
-    """Changes the player's volume"""
-
-    if ctx.voice_client is None:
-      return await ctx.send("Not connected to a voice channel.")
-
-    ctx.voice_client.source.volume = volume / 100
-    await ctx.send("Changed volume to {}%".format(volume))
+    await ctx.send(f"Now playing: {player.title}")
 
   @commands.command()
   async def stop(self, ctx):
-    """Stops and disconnects the bot from voice"""
-
     await ctx.voice_client.disconnect()
 
-  @play.before_invoke
-  @yt.before_invoke
   @stream.before_invoke
   async def ensure_voice(self, ctx):
     if ctx.voice_client is None:
       if ctx.author.voice:
         await ctx.author.voice.channel.connect()
       else:
-        await ctx.send("You are not connected to a voice channel.")
         raise commands.CommandError("Author not connected to a voice channel.")
     elif ctx.voice_client.is_playing():
       ctx.voice_client.stop()
 
 
-bot = commands.Bot(command_prefix=commands.when_mentioned_or("!"),
-                   description='Relatively simple music bot example')
+if __name__ == "__main__":
+  bot = commands.Bot(command_prefix=commands.when_mentioned_or("!"), description='Relatively simple music bot example')
 
+  @bot.event
+  async def on_ready():
+    print(f"Logged in as {bot.user} ({bot.user.id})")
+    print('------')
 
-@bot.event
-async def on_ready():
-  print('Logged in as {0} ({0.id})'.format(bot.user))
-  print('------')
+  bot.add_cog(Music(bot))
+  bot.add_cog(ErrorHandler(bot))
 
-bot.add_cog(Music(bot))
+  token = os.environ.get("BOT_TOKEN", None)
+  if not token:
+    print("No token found in BOT_TOKEN")
+    sys.exit(1)
 
-token = os.environ.get("BOT_TOKEN", None)
-if not token:
-  print("No token fouund in BOT_TOKEN")
-  exit(1)
-
-bot.run(token)
+  bot.run(token)
diff --git a/src/error.py b/src/error.py
new file mode 100644
index 0000000..2b4b457
--- /dev/null
+++ b/src/error.py
@@ -0,0 +1,25 @@
+from discord.ext import commands
+
+
+class ErrorHandler(commands.Cog):
+  """A cog for global error handling."""
+
+  def __init__(self, bot: commands.Bot):
+    self.bot = bot
+
+  @commands.Cog.listener()
+  async def on_command_error(self, ctx: commands.Context, error: commands.CommandError):
+    if isinstance(error, commands.CommandNotFound):
+      return
+    if isinstance(error, commands.MissingPermissions):
+      message = "You are missing the required permissions to run this command!"
+    elif isinstance(error, commands.UserInputError):
+      message = "Something about your input was wrong, please check your input and try again!"
+    else:
+      message = "Oh no! Something went wrong while running the command!"
+
+    await ctx.send(message)
+
+
+def setup(bot: commands.Bot):
+  bot.add_cog(ErrorHandler(bot))
diff --git a/src/yt.py b/src/yt.py
index 69d9592..8148bba 100644
--- a/src/yt.py
+++ b/src/yt.py
@@ -1,3 +1,6 @@
+import asyncio
+
+import discord
 import youtube_dl
 
 # Suppress noise about console usage from errors
diff --git a/test/conftest.py b/test/conftest.py
new file mode 100644
index 0000000..1fa415c
--- /dev/null
+++ b/test/conftest.py
@@ -0,0 +1,22 @@
+import sys
+from pathlib import Path
+from unittest.mock import Mock
+
+import pytest
+from pytest_mock import MockerFixture
+
+# Add source to PATH such that imports within src modules are properly resolved.
+SRC_PATH = str(Path(__file__).parent / '..' / 'src')
+sys.path.insert(0, SRC_PATH)
+
+
+@pytest.fixture
+def bot(mocker: MockerFixture):
+  bot_mock = mocker.patch('discord.ext.commands.Bot', autospec=True)
+  bot_mock.loop = Mock()
+  yield bot_mock
+
+
+@pytest.fixture
+def ctx(mocker: MockerFixture):
+  yield mocker.patch('discord.ext.commands.Context', autospec=True)
diff --git a/test/test_bot.py b/test/test_bot.py
new file mode 100644
index 0000000..1bbe70d
--- /dev/null
+++ b/test/test_bot.py
@@ -0,0 +1,54 @@
+from unittest.mock import Mock, AsyncMock, patch
+
+import pytest
+from discord.ext import commands
+
+from bot import Music
+
+
+@pytest.mark.asyncio
+async def test_bot_ensure_voice(bot, ctx):
+  mbot = Music(bot)
+
+  # 1. Inside a voice channel
+  # 1.1 Does not call stop if no sound is playing
+  ctx.voice_client.is_playing.return_value = False
+  await mbot.ensure_voice(ctx)
+  assert ctx.voice_client.stop.call_count == 0
+  ctx.reset_mock(return_value=True)
+
+  # 1.2 Does call stop if sound is playing
+  ctx.voice_client.is_playing.return_value = True
+  await mbot.ensure_voice(ctx)
+  assert ctx.voice_client.stop.call_count == 1
+  ctx.reset_mock(return_value=True)
+
+  # 2. Not inside a voice channel
+  # 2.1 Connects to voice channel of author if possible
+  ctx.voice_client = None
+  ctx.author.voice = AsyncMock()
+  await mbot.ensure_voice(ctx)
+  assert ctx.author.voice.channel.connect.call_count == 1
+  ctx.reset_mock(return_value=True)
+
+  # 2.2 Error if author not inside a channel
+  ctx.voice_client = None
+  ctx.author.voice = None
+  with pytest.raises(commands.CommandError):
+    await mbot.ensure_voice(ctx)
+
+
+@pytest.mark.asyncio
+async def test_bot_stream(bot, ctx):
+  mbot = Music(bot)
+
+  with patch('bot.YTDLSource', new_callable=AsyncMock) as ytdl_source:
+    player = Mock()
+    ytdl_source.from_url.return_value = player
+    url = 'A Day To Remember - All I Want'
+    # pylint: disable=too-many-function-args
+    await mbot.stream(mbot, ctx, url=url)
+    assert ytdl_source.from_url.await_args.args == (url,)
+    assert ytdl_source.from_url.await_args.kwargs == {"loop": bot.loop, "stream": True}
+    assert ctx.voice_client.play.call_args.args == (player,)
+    assert ctx.send.call_count == 1