diff --git a/.travis.yml b/.travis.yml
index 0253d7d..15ed377 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,49 +1,45 @@
 sudo: required
+
 env:
-  - >
-    container_id=$(mktemp)
-    distribution=centos
-    version=7
-    init=/usr/lib/systemd/systemd
-    run_opts="--privileged --volume=/sys/fs/cgroup:/sys/fs/cgroup:ro"
-  - >
-    container_id=$(mktemp)
-    distribution=ubuntu
-    version=14.04
-    init=/sbin/init
-    run_opts=""
+  # CentOS 7.
+  - container_id: $(mktemp)
+    distribution: centos
+    version: 7
+    init: /usr/lib/systemd/systemd
+    run_opts: "--privileged --volume=/sys/fs/cgroup:/sys/fs/cgroup:ro"
+  # Ubuntu 14.04.
+  - container_id: $(mktemp)
+    distribution: ubuntu
+    version: 14.04
+    init: /sbin/init
+    run_opts: ""
 
 services:
   - docker
 
 before_install:
   - sudo apt-get update
-  # Pull container
-  - sudo docker pull ${distribution}:${version}
-  # Customize container
-  - sudo docker build --rm=true --file=tests/Dockerfile.${distribution} --tag=${distribution}:ansible tests
+  # Pull container.
+  - "sudo docker pull ${distribution}:${version}"
+  # Customize container.
+  - "sudo docker build --rm=true --file=tests/Dockerfile.${distribution} --tag=${distribution}:ansible tests"
 
 script:
-  #
-  # Run test playbook
-  #
-
-    # Run container in detached state
+  # Run container in detached state.
   - sudo docker run --detach --volume="${PWD}":/etc/ansible/roles/role_under_test:ro ${run_opts} ${distribution}:ansible "${init}" > "${container_id}"
 
-    # Syntax check
-  - sudo docker exec --tty "$(cat ${container_id})" env TERM=xterm ansible-playbook /etc/ansible/roles/role_under_test/tests/test.yml --syntax-check
-    # Test role
-  - sudo docker exec --tty "$(cat ${container_id})" env TERM=xterm ansible-playbook /etc/ansible/roles/role_under_test/tests/test.yml
-    # Idempotence test
+  # Ansible syntax check.
+  - 'sudo docker exec --tty "$(cat ${container_id})" env TERM=xterm ansible-playbook /etc/ansible/roles/role_under_test/tests/test.yml --syntax-check'
+
+  # Test role.
+  - 'sudo docker exec --tty "$(cat ${container_id})" env TERM=xterm ansible-playbook /etc/ansible/roles/role_under_test/tests/test.yml'
+
+  # Test role idempotence.
   - >
     sudo docker exec "$(cat ${container_id})" ansible-playbook /etc/ansible/roles/role_under_test/tests/test.yml
     | grep -q 'changed=0.*failed=0'
     && (echo 'Idempotence test: pass' && exit 0)
     || (echo 'Idempotence test: fail' && exit 1)
 
-    # Clean up
-  - sudo docker stop "$(cat ${container_id})"
-
-notifications:
-  email: false
+  # Clean up
+  - 'sudo docker stop "$(cat ${container_id})"'
diff --git a/tests/Dockerfile.centos b/tests/Dockerfile.centos
index 888d502..8aa0654 100644
--- a/tests/Dockerfile.centos
+++ b/tests/Dockerfile.centos
@@ -1,4 +1,5 @@
 FROM centos:7
+
 # Install systemd -- See https://hub.docker.com/_/centos/
 RUN yum -y swap -- remove fakesystemd -- install systemd systemd-libs
 RUN yum -y update; yum clean all; \
@@ -10,14 +11,17 @@ rm -f /lib/systemd/system/sockets.target.wants/*udev*; \
 rm -f /lib/systemd/system/sockets.target.wants/*initctl*; \
 rm -f /lib/systemd/system/basic.target.wants/*; \
 rm -f /lib/systemd/system/anaconda.target.wants/*;
+
 # Install Ansible
 RUN yum -y install epel-release
 RUN yum -y install git ansible sudo
 RUN yum clean all
+
 # Disable requiretty
 RUN sed -i -e 's/^\(Defaults\s*requiretty\)/#--- \1/'  /etc/sudoers
+
 # Install Ansible inventory file
 RUN echo -e '[local]\nlocalhost ansible_connection=local' > /etc/ansible/hosts
-VOLUME [ "/sys/fs/cgroup" ]
-CMD ["/usr/sbin/init"]
 
+VOLUME ["/sys/fs/cgroup"]
+CMD ["/usr/sbin/init"]
diff --git a/tests/Dockerfile.ubuntu b/tests/Dockerfile.ubuntu
index 3dd5383..1475a46 100644
--- a/tests/Dockerfile.ubuntu
+++ b/tests/Dockerfile.ubuntu
@@ -1,9 +1,10 @@
 FROM ubuntu:14.04
+
 # Install Ansible
 RUN apt-get install -y software-properties-common git
 RUN apt-add-repository -y ppa:ansible/ansible
 RUN apt-get update
 RUN apt-get install -y ansible
+
 # Install Ansible inventory file
 RUN echo "[local]\nlocalhost ansible_connection=local" > /etc/ansible/hosts
-
diff --git a/tests/test.yml b/tests/test.yml
index 1edb57a..f5c5ca6 100644
--- a/tests/test.yml
+++ b/tests/test.yml
@@ -1,5 +1,6 @@
 ---
 - hosts: all
+
   vars:
     apache_listen_port_ssl: 443
     apache_create_vhosts: true
@@ -7,5 +8,6 @@
     apache_vhosts:
       - servername: "example.com"
         documentroot: "/var/www/vhosts/example_com"
+
   roles:
     - role_under_test