Travis config for testing on several versions of Laravel (or any other composer package if needed)

.travis.yml

language: php

php:
  - 5.6
  - 7.0
  - 7.1

cache:
  directories:
    - $HOME/.composer

env:
  - LARAVEL_VERSION=5.3.*
  - LARAVEL_VERSION=5.4.*

before_script:
  - composer self-update
  - if [ "LARAVEL_VERSION" != "" ]; then composer require "laravel/framework:${LARAVEL_VERSION}" --no-update; fi;
  - composer update

script:
  - vendor/bin/phpunit