Gulpfile.js

var gulp    = require('gulp');
var eslint  = require('gulp-eslint');
var babel   = require('gulp-babel');
var mocha   = require('gulp-mocha');
var del     = require('del');

gulp.task('clean', (cb) => 
    del('lib', cb)
);

gulp.task('lint', () => gulp
    .src([
        'src/**/*.js',
        'test/**/*.js',
        'Gulpfile.js'
    ])
    .pipe(eslint())
    .pipe(eslint.format())
    .pipe(eslint.failAfterError())
);

gulp.task('build', gulp.series(['clean', 'lint'], () => gulp
    .src('src/**/*.js')
    .pipe(babel())
    .pipe(gulp.dest('lib'))
));

gulp.task('test', gulp.series('build', () => gulp
    .src('test/**.js')
    .pipe(mocha({
        ui:       'bdd',
        reporter: 'spec',
        timeout:  typeof v8debug === 'undefined' ? 2000 : Infinity // NOTE: disable timeouts in debug
    }))
));

gulp.task('preview', gulp.series('build', (done) => {
    var buildReporterPlugin = require('testcafe').embeddingUtils.buildReporterPlugin;
    var pluginFactory       = require('./lib');
    var reporterTestCalls   = require('./test/utils/reporter-test-calls');
    var plugin              = buildReporterPlugin(pluginFactory);

    reporterTestCalls.forEach((call) => {
        plugin[call.method].apply(plugin, call.args);
    });

    done();
}));