Why does Codeception Acceptance tests sometimes pass tests sometimes not??

Question

Yii

$I->amOnPage(Url::to(['/user/token/run', 'token' => $I->grabFromDatabase('user_token', 'token')]));
here goes the direction to the controller
the browser opens the address
there in TokenController/actionRun
there is the code
Yii::$app->session->setFlash('success', Yii::t('user', 'You successfully changed your email.')) ;

and so in representation session the message sometimes is sometimes is not present.

Answer 1

Why is codeception selenium fooling
Or should it not work
Or should it work

Or it should either work or not work ... with the current implementation of your code
Causes of Heisenbugs
Also watch this video about Flacky tests
Andrey Solntsev - Flaky tests or an article if you don't like watching the video: https://habr.com/ru/company/ jugru/blog/416757/
Here is a link to the timing, why they happen and how to prevent them from happening: https://youtu.be/jLG3RXECQU8?t=2156