diff --git a/.dockerignore b/.dockerignore
new file mode 100644
index 00000000..88ac3066
--- /dev/null
+++ b/.dockerignore
@@ -0,0 +1,4 @@
+.git
+_build
+archlinux
+dist
diff --git a/.gitignore b/.gitignore
index 76de788b..26f66d4a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,3 +7,4 @@ tmp
 /*.geany
 *.out
 /_build
+/dist
diff --git a/.travis.yml b/.travis.yml
index eb187f2e..4cb97d3e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,70 +3,15 @@
 dist: xenial
 sudo: required
 language: python
-python: 2.7
+python: 3.7
 
-env:
--   MAX_CPU_PERCENT=20 MAX_MEM_PERCENT=5
+services:
+-   docker
 
 install:
 -   sudo apt-key update
 -   sudo apt-get -yq update
--   sudo apt -yq install xvfb gnome-shell
-
-# Install NodeJS from upstream, since the version that comes with Ubuntu 14 is ancient.
-# https://askubuntu.com/a/548776/13217
--   sudo apt-get -yq install curl
--   curl -sL https://deb.nodesource.com/setup_8.x | sudo -E bash -
--   sudo apt-get install -yq nodejs
-
-# Necessary on some versions of Ubuntu 14, which has a malformed npm/nodejs package.
--   sudo bash -c "[ ! -f /usr/bin/node ] && ln -s /usr/bin/nodejs /usr/bin/node || true"
--   which nodejs
--   which node
-
-# Install NPM from upstream.
--   git clone git://github.com/npm/cli.git
--   cd cli/scripts
--   chmod +x install.sh
--   sudo ./install.sh
--   cd ../..
-
--   sudo npm install -g eslint
-
-before_script:
-  - "export DISPLAY=:99.0"
-  - "/sbin/start-stop-daemon --start --quiet --pidfile /tmp/custom_xvfb_99.pid --make-pidfile --background --exec /usr/bin/Xvfb -- :99 -ac -screen 0 1280x1024x16"
-  - sleep 3 # give xvfb some time to start
-  - sudo gnome-shell &
-  - sleep 3 # give gnome-shell some time to start
 
 script:
-
-# Clear initial gnome-shell errors we don't care about.
--   sudo journalctl /usr/bin/gnome-shell
--   sudo journalctl --rotate
--   sudo journalctl --vacuum-time=1s
-
-# Show pre-extension gnome-shell performance.
--   ps -C gnome-shell -o %cpu,%mem,cmd
-
-# Run JSlint check.
--   cd $TRAVIS_BUILD_DIR
--   ./checkjs.sh
-
-# Install and enable extension.
--   sudo make install
--   gnome-shell-extension-tool --enable-extension=system-monitor@paradoxxx.zero.gmail.com
-
-# Give extension time to run.
--   sleep 10
-
-# Show post-extension gnome-shell performance.
--   ps -C gnome-shell -o %cpu,%mem,cmd
-# Check CPU. On localhost with 2.80GHz x 4 takes ~3%, on Travis ~15%.
--   bash -c '[[ $(bc <<< "$(ps -C gnome-shell -o %cpu|tail -1) < $MAX_CPU_PERCENT") -eq 1 ]]'
-# Check memory. On localhost with 32GB of memory, ~0.6%, on Travis ~3%.
--   bash -c '[[ $(bc <<< "$(ps -C gnome-shell -o %mem|tail -1) < $MAX_MEM_PERCENT") -eq 1 ]]'
-# Confirm extension hasn't thrown any errors.
--   sudo journalctl /usr/bin/gnome-shell
--   sudo journalctl /usr/bin/gnome-shell|grep "\-\- No entries \-\-"
+-   ./run_docker_tests.sh ubuntu1804
+-   ./run_docker_tests.sh ubuntu2004
diff --git a/Dockerfile.ubuntu1804 b/Dockerfile.ubuntu1804
new file mode 100644
index 00000000..c0c9f92a
--- /dev/null
+++ b/Dockerfile.ubuntu1804
@@ -0,0 +1,48 @@
+FROM ubuntu:18.04
+ENV PYTHONUNBUFFERED 1
+
+USER root
+ENV HOME /home/root
+
+# Install sudo. Not strictly required inside Docker, but it will allow Docker to run scripts that typically run outside Docker
+# which do use sudo.
+RUN apt update && apt -yq install sudo
+RUN sudo echo "hi"
+
+# Setup localization.
+ENV DEBIAN_FRONTEND noninteractive
+RUN apt update
+RUN apt install -y locales
+RUN rm -rf /var/lib/apt/lists/* && localedef -i en_US -c -f UTF-8 -A /usr/share/locale/locale.alias en_US.UTF-8
+RUN apt update
+ENV LANG en_US.utf8
+
+# Install dependencies
+RUN apt-get -yq update && apt-get install -y gnupg2
+RUN apt-key update
+RUN apt-get -yq update
+RUN apt-get -yq install xvfb gnome-shell git make bc dbus procps
+
+# Install NodeJS from upstream, since the version that comes with the distro is ancient.
+# https://askubuntu.com/a/548776/13217
+RUN apt-get -yq install curl
+RUN curl -sL https://deb.nodesource.com/setup_10.x | sudo -E bash -
+RUN apt-get install -yq nodejs
+
+# Necessary on some versions of Ubuntu 14, which has a malformed npm/nodejs package.
+RUN bash -c "[ ! -f /usr/bin/node ] && ln -s /usr/bin/nodejs /usr/bin/node || true"
+RUN which nodejs
+RUN which node
+
+# Install NPM from upstream.
+RUN git clone git://github.com/npm/cli.git
+RUN cd cli/scripts; chmod +x install.sh; ./install.sh
+RUN npm install -g eslint
+
+# Install code.
+RUN mkdir -p /home/root/git/gnome-shell-system-monitor-applet
+COPY . /home/root/git/gnome-shell-system-monitor-applet
+WORKDIR /home/root/git/gnome-shell-system-monitor-applet
+
+# Run test wrapper.
+CMD ./docker_cmd_ubuntu1804.sh
diff --git a/Dockerfile.ubuntu2004 b/Dockerfile.ubuntu2004
new file mode 100644
index 00000000..f3ac8767
--- /dev/null
+++ b/Dockerfile.ubuntu2004
@@ -0,0 +1,47 @@
+FROM ubuntu:20.04
+ENV PYTHONUNBUFFERED 1
+
+USER root
+
+# Install sudo. Not strictly required inside Docker, but it will allow Docker to run scripts that typically run outside Docker
+# which do use sudo.
+RUN apt update && apt -yq install sudo
+RUN sudo echo "hi"
+
+# Setup localization.
+ENV DEBIAN_FRONTEND noninteractive
+RUN apt update
+RUN apt install -y locales
+RUN rm -rf /var/lib/apt/lists/* && localedef -i en_US -c -f UTF-8 -A /usr/share/locale/locale.alias en_US.UTF-8
+RUN apt update
+ENV LANG en_US.utf8
+
+# Install dependencies
+RUN apt-get -yq update && apt-get install -y gnupg2
+RUN apt-key update
+RUN apt-get -yq update
+RUN apt-get -yq install xvfb gnome-shell git make bc dbus
+
+# Install NodeJS from upstream, since the version that comes with the distro is ancient.
+# https://askubuntu.com/a/548776/13217
+RUN apt-get -yq install curl
+RUN curl -sL https://deb.nodesource.com/setup_10.x | sudo -E bash -
+RUN apt-get install -yq nodejs
+
+# Necessary on some versions of Ubuntu 14, which has a malformed npm/nodejs package.
+RUN bash -c "[ ! -f /usr/bin/node ] && ln -s /usr/bin/nodejs /usr/bin/node || true"
+RUN which nodejs
+RUN which node
+
+# Install NPM from upstream.
+RUN git clone git://github.com/npm/cli.git
+RUN cd cli/scripts; chmod +x install.sh; ./install.sh
+RUN npm install -g eslint
+
+# Install code.
+RUN mkdir -p /home/root/git/gnome-shell-system-monitor-applet
+COPY . /home/root/git/gnome-shell-system-monitor-applet
+WORKDIR /home/root/git/gnome-shell-system-monitor-applet
+
+# Run test wrapper.
+CMD ./docker_cmd_ubuntu2004.sh
diff --git a/checkjs.sh b/checkjs.sh
index 85662761..3b578df7 100755
--- a/checkjs.sh
+++ b/checkjs.sh
@@ -1,4 +1,5 @@
 #!/bin/bash
 # Install eslint with:
 #   sudo apt-get install npm && sudo npm install -g eslint
+set -e
 eslint system-monitor@paradoxxx.zero.gmail.com
diff --git a/docker-compose.ubuntu1804.yml b/docker-compose.ubuntu1804.yml
new file mode 100644
index 00000000..c16246ec
--- /dev/null
+++ b/docker-compose.ubuntu1804.yml
@@ -0,0 +1,12 @@
+#https://docs.docker.com/compose/compose-file/#shm_size
+version: "3.5"
+services:
+
+  test:
+    build:
+      context: .
+      # Increase the size of shared memory.
+      # The default shared memory is only 64mb, causing odd Selenium errors like:
+      # selenium.common.exceptions.WebDriverException: Message: Failed to decode response from marionette
+      shm_size: '1gb'
+      dockerfile: Dockerfile.ubuntu1804
diff --git a/docker-compose.ubuntu2004.yml b/docker-compose.ubuntu2004.yml
new file mode 100644
index 00000000..26425883
--- /dev/null
+++ b/docker-compose.ubuntu2004.yml
@@ -0,0 +1,12 @@
+#https://docs.docker.com/compose/compose-file/#shm_size
+version: "3.5"
+services:
+
+  test:
+    build:
+      context: .
+      # Increase the size of shared memory.
+      # The default shared memory is only 64mb, causing odd Selenium errors like:
+      # selenium.common.exceptions.WebDriverException: Message: Failed to decode response from marionette
+      shm_size: '1gb'
+      dockerfile: Dockerfile.ubuntu2004
diff --git a/docker-compose.yml b/docker-compose.yml
new file mode 100644
index 00000000..494a0400
--- /dev/null
+++ b/docker-compose.yml
@@ -0,0 +1,11 @@
+#https://docs.docker.com/compose/compose-file/#shm_size
+version: "3.5"
+services:
+  test:
+    build:
+      context: .
+      # Increase the size of shared memory.
+      # The default shared memory is only 64mb, causing odd Selenium errors like:
+      # selenium.common.exceptions.WebDriverException: Message: Failed to decode response from marionette
+      shm_size: '1gb'
+      dockerfile: Dockerfile.${DISTRO}
diff --git a/docker_cmd_ubuntu1804.sh b/docker_cmd_ubuntu1804.sh
new file mode 100755
index 00000000..46935068
--- /dev/null
+++ b/docker_cmd_ubuntu1804.sh
@@ -0,0 +1,53 @@
+#!/bin/bash
+# Called from the Dockerfile.* to execute our tests via the CMD.
+set -e
+
+echo "[$(date)] Launching Dbus."
+mkdir -p /var/run/dbus
+dbus-daemon --config-file=/usr/share/dbus-1/system.conf --print-address
+sleep 3 # give Dbus some time to start
+
+echo "[$(date)] Launching Xvfb."
+export DISPLAY=:99.0
+/sbin/start-stop-daemon --start --quiet --pidfile /tmp/custom_xvfb_99.pid --make-pidfile --background --exec /usr/bin/Xvfb -- :99 -ac -screen 0 1280x1024x16
+sleep 3 # give xvfb some time to start
+
+echo "[$(date)] Launching Gnome-Shell."
+sudo gnome-shell &
+sleep 3 # give gnome-shell some time to start
+echo "[$(date)] Confirming Gnome-Shell is running."
+pgrep gnome-shell
+
+echo "[$(date)] Showing Gnome-Shell log entries."
+sudo journalctl /usr/bin/gnome-shell || true
+echo "[$(date)] Rotating Gnome-Shell log entries."
+sudo journalctl --rotate || true
+echo "[$(date)] Clearing Gnome-Shell log entries."
+sudo journalctl --vacuum-time=1s || true
+
+echo "[$(date)] Show pre-extension Gnome-Shell performance."
+ps -C gnome-shell -o %cpu,%mem,cmd || true
+
+echo "[$(date)] Running JSLint check."
+#cd $TRAVIS_BUILD_DIR
+./checkjs.sh
+
+echo "[$(date)] Installing extension."
+sudo make install
+gnome-shell-extension-tool --enable-extension=system-monitor@paradoxxx.zero.gmail.com
+sleep 10 # Give extension time to run.
+
+echo "[$(date)] Showing post-extension Gnome-Shell performance."
+export MAX_CPU_PERCENT=20
+export MAX_MEM_PERCENT=5
+ps -C gnome-shell -o %cpu,%mem,cmd
+# Check CPU. On localhost with 2.80GHz x 4 takes ~3%, on Travis ~15%.
+bash -c '[[ $(bc <<< "$(ps -C gnome-shell -o %cpu|tail -1) < $MAX_CPU_PERCENT") -eq 1 ]]'
+# Check memory. On localhost with 32GB of memory, ~0.6%, on Travis ~3%.
+bash -c '[[ $(bc <<< "$(ps -C gnome-shell -o %mem|tail -1) < $MAX_MEM_PERCENT") -eq 1 ]]'
+
+echo "[$(date)] Confirming extension hasn't thrown any errors."
+# Note, finding no entries returns an error code of 1, which in our case means no error.
+sudo journalctl /usr/bin/gnome-shell
+sudo journalctl /usr/bin/gnome-shell|grep "\-\- No entries \-\-"
+sudo journalctl --since=$(date '+%Y-%m-%d') /usr/bin/gnome-shell|grep -i "Extension \"system-monitor@paradoxxx.zero.gmail.com\" had error"
diff --git a/docker_cmd_ubuntu2004.sh b/docker_cmd_ubuntu2004.sh
new file mode 100755
index 00000000..2e99dc64
--- /dev/null
+++ b/docker_cmd_ubuntu2004.sh
@@ -0,0 +1,49 @@
+#!/bin/bash
+# Called from the Dockerfile.* to execute our tests via the CMD.
+set -e
+
+echo "[$(date)] Launching Dbus."
+mkdir -p /var/run/dbus
+dbus-daemon --config-file=/usr/share/dbus-1/system.conf --print-address
+sleep 3 # give Dbus some time to start
+
+echo "[$(date)] Launching Xvfb."
+export DISPLAY=:99.0
+/sbin/start-stop-daemon --start --quiet --pidfile /tmp/custom_xvfb_99.pid --make-pidfile --background --exec /usr/bin/Xvfb -- :99 -ac -screen 0 1280x1024x16
+sleep 3 # give xvfb some time to start
+
+echo "[$(date)] Launching Gnome-Shell."
+sudo gnome-shell &
+sleep 3 # give gnome-shell some time to start
+
+echo "[$(date)] Clearing Gnome-Shell log entries."
+sudo journalctl /usr/bin/gnome-shell || true
+sudo journalctl --rotate
+sudo journalctl --vacuum-time=1s
+
+echo "[$(date)] Show pre-extension Gnome-Shell performance."
+ps -C gnome-shell -o %cpu,%mem,cmd
+
+echo "[$(date)] Running JSLint check."
+#cd $TRAVIS_BUILD_DIR
+./checkjs.sh
+
+echo "[$(date)] Installing extension."
+sudo make install
+gnome-shell-extension-tool --enable-extension=system-monitor@paradoxxx.zero.gmail.com
+sleep 10 # Give extension time to run.
+
+echo "[$(date)] Showing post-extension Gnome-Shell performance."
+export MAX_CPU_PERCENT=20
+export MAX_MEM_PERCENT=5
+ps -C gnome-shell -o %cpu,%mem,cmd
+# Check CPU. On localhost with 2.80GHz x 4 takes ~3%, on Travis ~15%.
+bash -c '[[ $(bc <<< "$(ps -C gnome-shell -o %cpu|tail -1) < $MAX_CPU_PERCENT") -eq 1 ]]'
+# Check memory. On localhost with 32GB of memory, ~0.6%, on Travis ~3%.
+bash -c '[[ $(bc <<< "$(ps -C gnome-shell -o %mem|tail -1) < $MAX_MEM_PERCENT") -eq 1 ]]'
+
+echo "[$(date)] Confirming extension hasn't thrown any errors."
+# Note, finding no entries returns an error code of 1, which in our case means no error.
+sudo journalctl /usr/bin/gnome-shell
+sudo journalctl /usr/bin/gnome-shell|grep "\-\- No entries \-\-"
+sudo journalctl --since=$(date '+%Y-%m-%d') /usr/bin/gnome-shell|grep -i "Extension \"system-monitor@paradoxxx.zero.gmail.com\" had error"
diff --git a/run_docker_tests.sh b/run_docker_tests.sh
new file mode 100755
index 00000000..070e0090
--- /dev/null
+++ b/run_docker_tests.sh
@@ -0,0 +1,60 @@
+#!/usr/bin/env bash
+# The top-level user script for executing tests from Docker.
+# The first argument should be a distro identifier.
+
+export DISTRO=${1:-ubuntu1804}
+
+echo "[$(date)] Running $DISTRO tests."
+
+COMPOSE_FILE_LOC="docker-compose.yml"
+
+# This must match the name in the docker-compose.*.yml file.
+TEST_CONTAINER_NAME="test"
+
+COMPOSE_PROJECT_NAME_ORIGINAL="test_${BUILD_TAG}"
+echo "[$(date)] COMPOSE_PROJECT_NAME_ORIGINAL=$COMPOSE_PROJECT_NAME_ORIGINAL"
+
+# Project name is sanitized by Compose, so we need to do the same thing.
+# See https://github.com/docker/compose/issues/2119.
+COMPOSE_PROJECT_NAME=$(echo $COMPOSE_PROJECT_NAME_ORIGINAL | awk '{print tolower($0)}' | sed 's/[^a-z0-9]*//g')
+echo "[$(date)] COMPOSE_PROJECT_NAME=$COMPOSE_PROJECT_NAME"
+TEST_CONTAINER_REF="${COMPOSE_PROJECT_NAME}_${TEST_CONTAINER_NAME}_1"
+echo "[$(date)] TEST_CONTAINER_REF=$TEST_CONTAINER_REF"
+
+# Record installed version of Docker and Compose with each build
+echo "[$(date)] Docker environment:"
+docker --version
+docker-compose --version
+
+function cleanup {
+    echo "[$(date)] Shutting down..."
+    docker-compose -f $COMPOSE_FILE_LOC -p $COMPOSE_PROJECT_NAME down --remove-orphans
+    echo "[$(date)] Stopping..."
+    docker ps -a --no-trunc | grep $COMPOSE_PROJECT_NAME | awk '{print $1}' | xargs --no-run-if-empty docker stop
+    echo "[$(date)] Removing..."
+    docker ps -a --no-trunc | grep $COMPOSE_PROJECT_NAME | awk '{print $1}' | xargs --no-run-if-empty docker rm
+    echo "[$(date)] Delete old containers."
+    docker system prune -a -f
+}
+
+function run_tests {
+    echo "[$(date)] Creating containers..."
+    docker-compose -f $COMPOSE_FILE_LOC -p $COMPOSE_PROJECT_NAME up --build --force-recreate --exit-code-from test
+    ret_code=$?
+    echo "[$(date)] Docker Compose exit code: $ret_code"
+
+    # List images and containers related to this build
+    docker images | grep $COMPOSE_PROJECT_NAME | awk '{print $0}'
+    docker ps -a | grep $COMPOSE_PROJECT_NAME | awk '{print $0}'
+
+    # Follow the container with tests...
+    docker logs -f $TEST_CONTAINER_REF
+
+    exit $ret_code
+}
+
+set -e
+cleanup # Initial cleanup.
+trap cleanup EXIT # Cleanup after tests finish running
+
+run_tests
diff --git a/system-monitor@paradoxxx.zero.gmail.com/extension.js b/system-monitor@paradoxxx.zero.gmail.com/extension.js
index 9bdfea8b..37b246a1 100644
--- a/system-monitor@paradoxxx.zero.gmail.com/extension.js
+++ b/system-monitor@paradoxxx.zero.gmail.com/extension.js
@@ -49,7 +49,7 @@ var Me = ExtensionUtils.getCurrentExtension();
 var Convenience = Me.imports.convenience;
 var Compat = Me.imports.compat;
 
-var Background, GTop, IconSize, Locale, MountsMonitor, NM, NetworkManager, Schema, StatusArea, Style, gc_timeout, menu_timeout;
+var Background, GTop, IconSize, Locale, MountsMonitor, NM, NetworkManager, Schema, StatusArea, Style, TipItem, gc_timeout, menu_timeout;
 
 try {
     GTop = imports.gi.GTop;
@@ -661,10 +661,8 @@ const Pie = class SystemMonitor_Pie extends Graph {
     }
 }
 
-var TipItem = null;
-
 if (shell_Version < '3.36') {
-    var TipItem = class SystemMonitor_TipItem extends PopupMenu.PopupBaseMenuItem {
+    TipItem = class SystemMonitor_TipItem extends PopupMenu.PopupBaseMenuItem {
         constructor() {
             super();
             // PopupMenu.PopupBaseMenuItem.prototype._init.call(this);
@@ -673,11 +671,11 @@ if (shell_Version < '3.36') {
         }
     }
 } else {
-    var TipItem = GObject.registerClass(
+    TipItem = GObject.registerClass(
         {
             GTypeName: 'TipItem'
         },
-        class TipItem extends PopupMenu.PopupBaseMenuItem {
+        class SystemMonitor_TipItem extends PopupMenu.PopupBaseMenuItem {
             _init() {
                 super._init();
                 // PopupMenu.PopupBaseMenuItem.prototype._init.call(this);
@@ -687,6 +685,7 @@ if (shell_Version < '3.36') {
         }
     );
 }
+
 const TipMenu = class SystemMonitor_TipMenu extends PopupMenu.PopupMenuBase {
     constructor(sourceActor) {
         // PopupMenu.PopupMenuBase.prototype._init.call(this, sourceActor, 'sm-tooltip-box');