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Now that we had a look at unit tests,

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what they are, why we use them and integration tests,

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let's have a look at end-to-end tests or user interface tests. For this, I'll need to install another tool.

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So I'll quit my jest process here and I will install, with save dev, puppeteer, which is a headless version

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of Chrome, of the Chrome browser.

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So it basically is a browser we can use to interact with the DOM and so on,

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we can even run in a version with the head,

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so where we see the browser and we can basically define steps that should be executed in that browser

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so that we can automate certain processes on our web page

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and then of course test the result of these processes as well.

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Now this download will take a while because in the end it downloads the entire Chrome codebase because

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it needs that to be able to simulate that browser

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ANd once it's done, I'll be back.

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So I'm done installing it,

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LEt's start using puppeteer now and for that, I'll go to my utiltest.js file and I will import puppeteer.

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So I'll import puppeteer by requiring it from puppeteer like this and I will write a new test

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now and there, I will just write should click around for now, we'll fix this later or change this later

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and in this function which should be executed here, I want to use puppeteer.

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Now how can I use it?

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First of all I set up a browser by using puppeteer launch.

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Now this will launch a browser with some options which I can define here,

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for example I can set headless to false to actually run a browser with a user interface as well,

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you can set a bunch of stuff here and you can find it all in the official docs of puppeteer of course.

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I will also set slomo here,

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that will basically slow down the automated operations so that we have a chance of seeing what's happening

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and I'll set it to a value of 80 and we can also set some args here which is an array where I can

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pass dash dash in and for example window size to launch this browser with these arguments and window

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size allows me to set a width height pair, so I can set this to 1920 and 1080 for

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example, like this, this should launch a browser with this size and that of course can be great

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to also test if certain responsive features are working the way you want.

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So now this will create a browser.

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Now actually, this will return a promise,

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so we can use async await here if we want to by placing async in front of this pair of arguments here

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or this empty argument list

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and now we can await this to launch. The alternative would be to just use then and catch, async await

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in the end does this for you.

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So here I'm awaiting this and storing the result in browser you could say, as a next step,

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I can now create a page object by awaiting the browser to create a new page, like this.

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Now I'll also need to tell the browser which page to load and I'll grab my URL here and then we can

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say page, go to

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and then you enter your URL which should be loaded and you also should await this because all these

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browser related things are promises that simply take some time to execute

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so you have to await each step.

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So now this should open a browser and load this page.

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Let's try this by running npm test and it should indeed open up a brand new window in Chromium which

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is basically like a Chrome or

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the core functionality of Chrome and you also see that this is being tested or controlled by automated

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test software.

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So this was opened automatically,

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now let's go back and let's add some logic here.

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We don't just want to go to that page,

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let's say we also want to enter something. For that I want to enter something into my input with the

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ID name and age,

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so in my test I will await a step or I use that page where I navigate into my app where I will then

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click into the field with that selector, so click takes the selector of the item it should click on.

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Once I click there, I will type

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and again you can find all commands in the official puppeteer docs, so you can really like instruct

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the browser, the headless browser,

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what to do. So I want to type and I want to type into the same input and we wouldn't have to click on

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it first but I want to simulate all the steps a user would do

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and I want to insert let's say Anna here to mix it up, not always Max.

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So now I type in there,

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I will repeat these steps once I type the name for the age,

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so for the age field I will enter 28 let's say. And if you save that,

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it will open up a new window where you can see that it enters

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these things. Now we can now also add another step and click on this button at the bottom of our page,

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so in app.js, in the end it's this button we're listening on for an event here with ID button add

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user. We can grab that selector and make sure we click on that in our setup and now we get a full flow setup

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where you see that this gets entered and then we click this button here at the end. You also saw that

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it didn't add an item and this already shows us that writing this text was not the worst idea because

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it looks like something was broken and indeed here in our automated test, if we open the developer tools,

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we see that it didn't find the validate input function here. So since that was missing or is missing,

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we have to check our util.js file and see what's wrong with validate input in here I'm using validate

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input here and I'm defining it as a function here

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but one thing I never did is I never recompiled my code,

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that's something we have to do because the code that gets imported in the browser is packed with webpack

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and I never recompiled it after changing my code.

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So in a separate terminal window, I'll quickly run npm start to get webpack to run my code and

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It'll now also watch my code and recompile if I change something

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and with that, it should have executed your test automatically, in case it didn't, simply add a blank and

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reopen your browser and enter and it will reopen the browser and execute this

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and now you see this works and this puppeteer being used for automated testing with a graphical user

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interface.

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Now obviously, we can automate this a bit more and check the result programmatically now to see if we

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got to the expected outcome because what I can now do is I can also await 

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and now that everything executed I can check if something is the case,

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for example I can check for the existence of this list item with a class of user item being added to

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it. So in my test, I can await my page and there, I can use $eval to get access to an element and

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I will look for the first element with a class of user item and I pass a function as a second argument

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to eval where I then define what I want to do with the element I selected there and here I will

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get an element as an input and I will for example return the text content

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and this means that now the result of this function will be returned by this overall promise,

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so I can store it here.

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Final text for example will be the text that I fetch from this element that was created and now I can

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expect final text to be Anna, 28 years old.

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Now it's again checking for that text but it's now using the full flow in the browser,

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it's not just a unit or integration test as we have it up there,

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it's really going through all the steps we would execute manually as well

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and then of course we should have that text but we could check anything here.

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We could also check for the existence of this class and we implicitly do so because if that class would

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not be there, we couldn't select the element by it and therefore for final text would certainly not be

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that text but now if I save this, it executes all our steps here and it actually fails here because it basically

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timed out and

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that's just a limit set up by jest to ensure that our tests don't take too long. What we can do for that

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is the test function actually takes a third argument and that is the maximum timeout and we can set

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this to 10 seconds to 10000 to increase the time we give our browser to complete its operation

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so that it doesn't timeout

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and now you see it finishes successfully because should click around, to which we should assign a better

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name, does give us the result we want

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and here I will now say should create an element with text and correct class, something like this.

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By the way we can of course now also set headless to true, disable the slow motion and not set these

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arguments

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and this will now speed up the testing because now it doesn't have to go through that step in a real

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browser, it does so behind the scenes

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and that's one of the advantages of having a headless browser, that you don't have to watch it execute

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the steps but it can be nice to see the steps, you can do both

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and now we got a full e-to-e test or a user interface test in place too.