diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..8b7ef35
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+/vendor
+composer.lock
diff --git a/.travis.yml b/.travis.yml
index 9e68280..8c11a5a 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,17 +2,20 @@ language: php
 sudo: false
 
 php:
-  - 5.5
   - 5.6
   - 7.0
 
 env:
-  matrix:
-  - DRUPAL_CORE=8.1.x
-  - DRUPAL_CORE=8.2.x
-  global:
-    MODULE_NAME='message_subscribe'
-    CODER_VERSION='8.2.*'
+  - TEST_SUITE=8.1.x
+  - TEST_SUITE=8.2.x
+  - TEST_SUITE=8.3.x
+  - TEST_SUITE=PHP_CodeSniffer
+
+# Only run the coding standards check once.
+matrix:
+  exclude:
+    - php: 5.6
+      env: TEST_SUITE=PHP_CodeSniffer
 
 mysql:
   database: drupal
@@ -25,8 +28,14 @@ before_script:
   # We also don't care if that file exists or not on PHP 7.
   - phpenv config-rm xdebug.ini || true
 
+  # Make sure Composer is up to date.
+  - composer self-update
+
   # Remember the current directory for later use in the Drupal installation.
-  - TESTDIR=$(pwd)
+  - MODULE_DIR=$(pwd)
+
+  # Install Composer dependencies.
+  - composer install
 
   # Navigate out of module directory to prevent blown stack by recursive module
   # lookup.
@@ -35,45 +44,25 @@ before_script:
   # Create database.
   - mysql -e 'create database drupal'
 
-  # Export database variable for kernel tests.
-  - export SIMPLETEST_DB=mysql://root:@127.0.0.1/drupal
+  # Download Drupal 8 core. Skip this for the coding standards test.
+  - test ${TEST_SUITE} == "PHP_CodeSniffer" || travis_retry git clone --branch $TEST_SUITE --depth 1 https://git.drupal.org/project/drupal.git
 
-  # Download Drupal 8 core.
-  - travis_retry git clone --branch $DRUPAL_CORE --depth 1 https://git.drupal.org/project/drupal.git
-  - cd drupal
-
-  # Download dependencies.
-  # @todo Specify in `require` and `require-dev` in `composer.json`
-  - cd modules
-  - travis_retry git clone --branch 8.x-1.x --depth 1 https://github.com/Gizra/og.git
-  - travis_retry git clone --branch 8.x-4.x --depth 1 https://git.drupal.org/project/flag.git
-  - travis_retry git clone --branch 8.x-1.x --depth 1 https://github.com/Gizra/message.git
-  - travis_retry git clone --branch 8.x-1.x --depth 1 https://github.com/Gizra/message_notify.git
-  - cd ..
+  # Remember the Drupal installation path.
+  - DRUPAL_DIR=$(pwd)/drupal
 
-  # Install Composer dependencies on 8.1.x and above.
-  - test ${DRUPAL_CORE} == "8.0.x" || composer self-update && composer install
-
-  # Coder.
-  - composer global require drupal/coder:$CODER_VERSION
-  - ln -s ~/.composer/vendor/drupal/coder/coder_sniffer/Drupal ~/.composer/vendor/squizlabs/php_codesniffer/CodeSniffer/Standards/
-
-  # Reference OG in the Drupal site.
-  - ln -s $TESTDIR modules/$MODULE_NAME
+  # Install Composer dependencies for core. Skip this for the coding standards test.
+  - test ${TEST_SUITE} == "PHP_CodeSniffer" || composer install --working-dir=$DRUPAL_DIR
 
   # Start a web server on port 8888 in the background.
-  - nohup php -S localhost:8888 > /dev/null 2>&1 &
+  - test ${TEST_SUITE} == "PHP_CodeSniffer" || nohup php -S localhost:8888 --docroot $DRUPAL_DIR > /dev/null 2>&1 &
 
   # Wait until the web server is responding.
-  - until curl -s localhost:8888; do true; done > /dev/null
+  - test ${TEST_SUITE} == "PHP_CodeSniffer" || until curl -s localhost:8888; do true; done > /dev/null
 
   # Export web server URL for browser tests.
   - export SIMPLETEST_BASE_URL=http://localhost:8888
 
-script:
-  # Coding standards.
-  - $HOME/.composer/vendor/bin/phpcs --report=full --standard=Drupal $TESTDIR
-  # Run the PHPUnit tests which also include the kernel tests.
-  - ./vendor/phpunit/phpunit/phpunit -c ./core/phpunit.xml.dist ./modules/$MODULE_NAME
-  # Run legacy simpletests.
-  - php core/scripts/run-tests.sh --color --verbose --php `which php` --directory modules/$MODULE_NAME/src/Tests --dburl $SIMPLETEST_DB --url $SIMPLETEST_BASE_URL --sqlite ./.db.sqlite
+  # Export database variable for kernel tests.
+  - export SIMPLETEST_DB=mysql://root:@127.0.0.1/drupal
+
+script: DRUPAL_DIR=$DRUPAL_DIR MODULE_DIR=$MODULE_DIR $MODULE_DIR/scripts/travis-ci/run-test.sh $TEST_SUITE
diff --git a/composer.json b/composer.json
index 6f25798..0cfcf7a 100644
--- a/composer.json
+++ b/composer.json
@@ -15,7 +15,8 @@
       "drupal/message_notify": "~8.1.0"
     },
     "require-dev": {
-      "drupal/og": "~8.1.0"
+      "drupal/og": "~8.1.0",
+      "drupal/coder": "^8.2"
     },
     "minimum-stability": "dev"
 }
diff --git a/phpcs-ruleset.xml.dist b/phpcs-ruleset.xml.dist
new file mode 100644
index 0000000..6141b63
--- /dev/null
+++ b/phpcs-ruleset.xml.dist
@@ -0,0 +1,17 @@
+<?xml version="1.0"?>
+<!-- PHP_CodeSniffer standard for Drupal modules. -->
+<!-- See http://pear.php.net/manual/en/package.php.php-codesniffer.annotated-ruleset.php -->
+<ruleset name="Drupal Module">
+    <description>Drupal coding standard for contributed modules</description>
+
+    <!-- Exclude unsupported file types. -->
+    <exclude-pattern>*.gif</exclude-pattern>
+    <exclude-pattern>*.less</exclude-pattern>
+    <exclude-pattern>*.png</exclude-pattern>
+
+    <!-- Minified files don't have to comply with coding standards. -->
+    <exclude-pattern>*.min.css</exclude-pattern>
+    <exclude-pattern>*.min.js</exclude-pattern>
+
+    <rule ref="./vendor/drupal/coder/coder_sniffer/Drupal" />
+</ruleset>
diff --git a/phpcs.xml b/phpcs.xml
new file mode 100644
index 0000000..56d8b74
--- /dev/null
+++ b/phpcs.xml
@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ruleset name="pbm_default">
+  <description>Default PHP CodeSniffer configuration for Messages.</description>
+  <rule ref="phpcs-ruleset.xml.dist"/>
+  <arg name="extensions" value="php,inc,module,install,info,test,profile,theme,css,js"/>
+  <arg name="report" value="full"/>
+  <arg value="p"/>
+  <file>.</file>
+  <exclude-pattern>./vendor</exclude-pattern>
+</ruleset>
diff --git a/scripts/travis-ci/run-test.sh b/scripts/travis-ci/run-test.sh
new file mode 100755
index 0000000..42b57b1
--- /dev/null
+++ b/scripts/travis-ci/run-test.sh
@@ -0,0 +1,18 @@
+#!/bin/bash
+
+# Run either PHPUnit tests or PHP_CodeSniffer tests on Travis CI, depending
+# on the passed in parameter.
+
+case "$1" in
+    PHP_CodeSniffer)
+        cd $MODULE_DIR
+        composer install
+        ./vendor/bin/phpcs
+        exit $?
+        ;;
+    *)
+        ln -s $MODULE_DIR $DRUPAL_DIR/modules/message_subscribe
+        cd $DRUPAL_DIR
+        ./vendor/bin/phpunit -c ./core/phpunit.xml.dist $MODULE_DIR/tests
+        exit $?
+esac