Mocha and Selenium WebDriver error thrown while assertion - node.js

Question

I developing a web program with TDD methodology. Therefore, tests are using Selenium WebDriver library. But I wonder my program doesn't work correctly. Following is source codes.
public/index.html:
<h1 class="hello">Hello, world!</h1>
test/test.js:
'use strict'
var assert = require('assert')
var webdriver = require('selenium-webdriver'),
By = webdriver.By,
until = webdriver.until
var driver;
before(() => {
driver = new webdriver.Builder()
.forBrowser('chrome')
.build()
})
describe('Index page', () => {
before(() => {
driver.get('http://localhost:8080/')
})
it('should show hello greetings', () => {
let hello = driver.findElement(By.css('h1.hello'))
assert.equal(hello.getText(), 'Hello, world!')
})
})
package.json:
{
"name": "foobar",
"version": "1.0.0",
"description": "",
"main": "index.js",
"devDependencies": {
"mocha": "^2.5.3"
"selenium-webdriver": "^2.53.2"
},
"scripts": {
"start": "http-server public",
"test": "mocha"
},
"author": "",
"license": "ISC"
}
And I've run following command.
C:\Projects\foobar>npm install
So, when I run all tests with npm test command, it always failed regardless to npm start command was run or not.
C:\Projects\foobar>npm test
> foobar#1.0.0 test C:\Projects\foobar
> mocha
Index page
1) should show hello greetings
0 passing (62ms)
1 failing
1) Index page should show hello greetings:
AssertionError: ManagedPromise {
flow_:
ControlFlow {
propagateUnhandledRejections_: true,
activeQueue_:
TaskQueue {
== 'Hello, world!'
at Context.<anonymous> (C:\Projects\foobar\test\test.js:22:16)
at callFn (C:\Projects\foobar\node_modules\mocha\lib\runnable.js:326:21)
at Test.Runnable.run (C:\Projects\foobar\node_modules\mocha\lib\runnable.js:319:7)
at Runner.runTest (C:\Projects\foobar\node_modules\mocha\lib\runner.js:422:10)
at C:\Projects\foobar\node_modules\mocha\lib\runner.js:528:12
at next (C:\Projects\foobar\node_modules\mocha\lib\runner.js:342:14)
at C:\Projects\foobar\node_modules\mocha\lib\runner.js:352:7
at next (C:\Projects\foobar\node_modules\mocha\lib\runner.js:284:14)
at Immediate._onImmediate(C:\Projects\foobar\node_modules\mocha\lib\runner.js:320:5)
npm ERR! Test failed. See above for more details.
I think the main issue is in hello.getText() snippet. The getText() method couldn't get text of hello element.

Answer 1

Most driver operations are asynchronous and return a promise, not the actual return value of that operation. In your case you should change findElement but also getText to work in that manner. Also, you should set a timeout since the default one is set to 2000 ms and most pages won't have finished loading by then. Try this:
'use strict'
var assert = require('assert');
var webdriver = require('selenium-webdriver');
var By = webdriver.By;
var until = webdriver.until;
var driver;
before(function () {
driver = new webdriver.Builder()
.forBrowser('chrome')
.build();
});
describe('Index page', function () {
this.timeout(5000);
before(function () {
driver.get('http://localhost:8080/');
});
it('should show hello greetings', function (done) {
driver.findElement(By.css('h1.hello'))
.then(elem => elem.getText() )
.then(text => assert.equal(text, 'Hello, world!') )
.then(done);
});
});
Note that arrow function don't define their own this object. You have to use regular callback functions to access this.timeout. Their use is, in any case, discouraged in mocha, see following:
Passing arrow functions to Mocha is discouraged. Their lexical binding of the this value makes them unable to access the Mocha context, and statements like this.timeout(1000); will not work inside an arrow function.