How to use travis-ci to test an application built on Laravel?

I have a written application with the support of Laravel Framework. I would like to carry out the implantation and unit test via Travis CI. Taking an example of the repository itself I was able to reach this solution:

language: php

env:
  global:
    - setup=stable

matrix:
  fast_finish: true
  include:
    - php: 7.1
    - php: 7.1
      env: setup=lowest
    - php: 7.2
    - php: 7.2
      env: setup=lowest

sudo: false

cache:
  directories:
    - $HOME/.composer/cache

services:
  - memcached
  - mysql

before_script:
  - cp .env.example .env
  - php artisan key:generate

before_install:
  - phpenv config-rm xdebug.ini || true
  - echo "extension = memcached.so" >> ~/.phpenv/versions/$(phpenv version-name)/etc/php.ini
  - travis_retry composer self-update
  - mysql -e 'CREATE DATABASE homestead CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;'
  - mysql -e "CREATE USER 'homestead'@'127.0.0.1' IDENTIFIED BY 'secret'; GRANT ALL PRIVILEGES ON *.* TO 'homestead'@'127.0.0.1' WITH GRANT OPTION; FLUSH PRIVILEGES;"
  - sudo service mysql restart

install:
  - if [[ $setup = 'stable' ]]; then travis_retry composer update --prefer-dist --no-interaction --prefer-stable --no-suggest; fi
  - if [[ $setup = 'lowest' ]]; then travis_retry composer update --prefer-dist --no-interaction --prefer-lowest --prefer-stable --no-suggest; fi

script:
  - vendor/bin/phpunit

Apparently it works perfectly, but is this approach correct against possible test / deployment patterns?

Another thing I did not understand very well was:

if [[ $setup = 'lowest' ]]; then travis_retry composer update --prefer-dist --no-interaction --prefer-lowest --prefer-stable --no-suggest;