wdio suite usage?

gistfile1.txt

$ npm install
$ ./node_modules/.bin/wdio --suite=test/google.js

google.js

// test/google.js

const assert = require('assert');

describe('google.com', function() {
    it('shows a title of page', function() {
        browser.url('https://google.com');
        assert(browser.getTitle() !== '');
    });
});

package.json

{
  "name": "wdio-bug",
  "version": "0.0.0",
  "private": true,
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "wdio-mocha-framework": "^0.3.1",
    "webdriverio": "^4.0.9"
  }
}

wdio.conf.js

exports.config = {
    specs: [
        './tests/*.js'
    ],
    exclude: [
    ],
    maxInstances: 10,
    capabilities: [{
        maxInstances: 5,
        browserName: 'firefox'
    }],
    sync: true,
    logLevel: 'result',
    coloredLogs: true,
    screenshotPath: './errorShots/',
    baseUrl: 'http://localhost',
    waitforTimeout: 10000,
    connectionRetryTimeout: 90000,
    connectionRetryCount: 3,
    framework: 'mocha',
    mochaOpts: {
        ui: 'bdd'
    },
}

yahoo.js

// test/yahoo.js

const assert = require('assert');

describe('yahoo.com', function() {
    it('shows a title of page', function() {
        browser.url('https://yahoo.com');
        assert(browser.getTitle() !== '');
    });
});