CODEWITHSUNDEEP
async-awaitprotractor
ohno60
ohno60

Reputation: 11

I'd like to use Async/await and onPrepare to make sure my tests don't start until onPrepare is complete

I want onPrepare to finish before any tests are run and I'm using async / await.

I'm new to javascript and protractor but I've been writing test automation for a couple of decades. This seems like an incredibly simple thing to want to do, have onPrepare finish before a test starts, but I'm confused my everything I've seen out there. I've set SELENIUM_PROMISE_MANAGER: false so I don't want to use promises to do this, right? My landing page in anguler do I use async and await on onPrepare or browser.driver.wait or webdriver.until.elementLocated? If so, do I put 'await' before those waits? (That seems redundant)

onPrepare: async() => { 
  await browser.driver.get( 'https://localhost:8443/support-tool/#/service/config'); 
  await browser.driver.findElements(by.className('mat-table')); 
  browser.driver.wait(webdriver.until.elementLocated(by.css('mat-select-value')), 10000);//(Returns webdriver not defined)
},

first, I get webdriver not defined when I run it. Once I get it to work, will my tests wait for onPrepare to be completed before they start running?

Upvotes: 0

Views: 742

Answers (1)

DublinDev
DublinDev

Reputation: 2348

So Protractor is a wrapper for the webdriverJS and webdriverJS is completely asynchronous. To give a very high level definition, Protractor wraps webdriverJS up so that every action returns a promise (for instance .get(), .sendKeys(), .findElement()).

Previously webdriverJS had what is referred to as the 'control flow' which allowed users to write code as they would in any synchronous programming language and the fact the almost everything is a promise was handled behind the scenes. This feature has been deprecated in the latest versions and the main reason is that the introduction of the async/await style of handling promises makes it much easier for users to manage promises ourselves.

If you are using protractor 6.0+ the control flow is disabled by default but it will be disabled for you regardless as you have you have set SELENIUM_PROMISE_MANAGER: false. You will need to manually manage your promises, which you are doing, by using async/await.

browser.driver vs browser

I also want to point out the by using browser.driver.get you are referring to the underlying selenium instance and not the protractor wrapper instance therefore it will not wait for the angular page to stabilize before interacting (I could be mistaken on this). There is more info on the distinction in this thread.

Any action that involves the browser or the file system will likely be a promise so include the await before them and any function that contains an await needs to be declared async.

I would write your code as follows:

onPrepare: async() => { 
    await browser.get('https://localhost:8443/support-tool/#/service/config'); 

    let someElement = await element(by.css('mat-select-value'));
    await browser.wait(protractor.ExpectedConditions.presenceOf(someElement), 10000);
  },

Finally, as long is your onPrepare is using awaits properly it should for sure complete before your tests begin.

Hope that helps and is clear, it was longer than I anticipated.

Upvotes: 1

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