CODEWITHSUNDEEP
javascripttestingautomated-testse2e-testingtestcafe
Vladimir_314159
Vladimir_314159

Reputation: 1677

The Error message ""index" argument is expected to be a number, but it was number" is unclear

While writing automated test for a website I got the following very odd error in here are the relovent lines of code: 

  68    let selected
  69    if( params.includes('-RB') ){
  70         let books = Selector('.actions > .link-learn > div').withText('VIEW PRODUCT')
  71         const index = books.count
  72         selected = books.nth( Math.floor(Math.random() * index) );
  73     }

and testcafe is making the following complaint at line 72.

 "index" argument is expected to be a number, but it was number.

And there are no strings, variables, etc. named with name number in my program. So what does this error mean and maybe this error should throw a different message that is slightly more clear.

thanks

Upvotes: 2

Views: 750

Answers (1)

Andrey Belym
Andrey Belym

Reputation: 2903

You have missed await on the line 71. It must be

const index = await books.count

Without await, you get a Promise wrapper instead of the actual count property. On the next line, the Promise turns into NaN (not a number) in the Math.random() * index expression. Type validation fails because NaN is not a valid number, but in JavaScript NaN belongs to the number type, which is reported in error message. That's why error report has the silly expected to be a number, but it was number message.

Thank your for the feedback and helping me to capture a bug, I've created an issue about it: https://github.com/DevExpress/testcafe/issues/2470. I think we will fix it in the next release.

Upvotes: 5

Related Questions