gulpfile.js

var gulp = require('gulp');
var connect = require('gulp-connect');
var mocha = require('gulp-mocha');
var eslint = require('gulp-eslint');

var files = ['index.js', 'gulpfile.js'];

gulp.task('lint', function () {
  return gulp.src(files).pipe(eslint()).pipe(eslint.format());
  // .pipe(eslint.failAfterError());
});

gulp.task('test', function () {
  var startServer = gulp.task('start-server');
  startServer();
  return gulp
    .src('test/*.js', { read: false })
    .pipe(mocha({ timeout: 5000 }))
    .on('end', connect.serverClose);
});

gulp.task('test:w', function () {
  var startServer = gulp.task('start-server');
  startServer();
  return gulp
    .src('test/*.js', { read: false })
    .pipe(mocha({ timeout: 5000, watch: true }))
    .on('end', connect.serverClose);
});

gulp.task('default', gulp.series(['lint', 'test']));

gulp.task('watch', function () {
  gulp.watch(files, gulp.series(['lint', 'test']));
});

gulp.task('start-server', function () {
  connect.server({
    root: './test',
    port: 1234,
  });
});

gulp.task('close-server', function () {
  connect.serverClose();
});