protractor-mocha-tags.js

// Note: ES6 syntax requires a version of Node.js >= 4.0.0
'use strict';

// Can use any lib (or none, if you choose) to parse args.
// "npm install yargs --save" to use this example as-is
let argv = require('yargs').argv;

const DELIMITER = ',';
const TAG_IDENT = '#';
let tagsOpt = typeof argv.tags === 'string' && argv.tags;
let grepString, tags;

if (tagsOpt) {
    tags = tagsOpt.split(DELIMITER);
    grepString = tags.map(tag => `${TAG_IDENT}${tag}`).join('|');
}

module.exports = function getMochaTags() {
    return grepString;
};

protractor.conf.js

// Note: ES6 syntax requires a version of Node.js >= 4.0.0
'use strict';

let tags = require('./protractor-mocha-tags')();

exports.config = {
    framework: 'mocha',
    capabilities: { browserName: 'chrome' },
    specs: ['tests/**/*.spec.js'],
    mochaOpts: {
        reporter: 'spec',
        grep: tags
    }
};

test.spec.js

// Note: ES6 syntax requires a version of Node.js >= 4.0.0
'use strict';

describe('Some Feature/Page #feature1', function() {
    it('should do some thing #slow', () => {
        // assertions
    });
});