index.js

var fs = require('fs');
var path = require('path');
var yaml = require('js-yaml');

module.exports = {
    getOptions: function () {
        return [];
    },

    updateTravis,

    run: function (directory, opts) {
        return Promise.all([
            getTravisFileByName(directory, '.travis')
        ]).then(([travis]) => {
            return new Promise(function (resolve, reject) {
                if (!travis) {
                    travis = path.join(directory, '.travis.yml');
                    return resolve('');
                }
                fs.readFile(travis, {encoding: 'utf8'}, function (error, text) {
                    error ? reject(error) : resolve(text);
                });
            }).then(function (text) {
                var travis = updateTravis(text);
                return travis;
            }).then(function (newText) {
                return new Promise(function (resolve, reject) {
                    fs.writeFile(travis, newText, function (error) {
                        error ? reject(error) : resolve();
                    });
                });
            });
        });
    }
};

function getTravisFileByName(directory, name){
    return new Promise((resolve, reject) => {
        fs.readdir(directory, (err, files) => {
            if(err) return reject(err);
            var fileName = files.find(item => {
                item = item.toLowerCase();
                return item.startsWith(name) && item.endsWith('yml') || item === name;
            });
            resolve(fileName ? path.join(directory, fileName) : null);
        });
    });
}

function updateTravis(text) {
    let ymlObject =  yaml.load(text);
    ymlObject.dist = "xenial";
    if (ymlObject.before_install) {
        delete ymlObject.before_install;
    }
    const services = `services:\n  - xvfb`;
    const servicesObject = yaml.load(services);
    Object.assign(ymlObject, servicesObject);
    return yaml.safeDump(ymlObject);
}