Travis CI ".travis.yml" config file for ESP8266 and Arduino IDE

.travis.yml

language: c
env:
  - BD=esp8266:esp8266:nodemcuv2:CpuFrequency=80,FlashSize=4M3M
before_install:
  - "/sbin/start-stop-daemon --start --quiet --pidfile /tmp/custom_xvfb_1.pid --make-pidfile --background --exec /usr/bin/Xvfb -- :1 -ac -screen 0 1280x1024x16"
  - sleep 3
  - export DISPLAY=:1.0
  - wget http://downloads.arduino.cc/arduino-1.8.2-linux64.tar.xz
  - tar xf arduino-1.8.2-linux64.tar.xz
  - sudo mv arduino-1.8.2 /usr/local/share/arduino
  - sudo ln -s /usr/local/share/arduino/arduino /usr/local/bin/arduino
install:
  - ln -s $PWD /usr/local/share/arduino/libraries/
  - arduino --pref "boardsmanager.additional.urls=http://arduino.esp8266.com/stable/package_esp8266com_index.json" --save-prefs
  - arduino --install-boards esp8266:esp8266
  - arduino --board $BD --save-prefs
  - arduino --pref "compiler.warning_level=all" --save-prefs
  
  # install lib
  # add your libs here, example:
  #- git clone https://github.com/squix78/esp8266-oled-ssd1306 /usr/local/share/arduino/libraries/esp8266-oled-ssd1306
  
script:
#compile the code, example:
# - arduino --verify --board $BD $PWD/path_to_the_file/file.ino

notifications:
  email:
    on_success: change
    on_failure: change

A possible problem could occur with the Arduino version.
For ESP8266: version 1.8.2
For Arduino: 1.6.9