Problem/Motivation
We want to get rid of simpletest.module in Drupal 9. We want to prepare the latest Drupal 8 development branch as much as possible before opening the Drupal 9 development branch (see #2608062: [policy, no patch] Pre-requisites for opening Drupal 9). Therefore we need to convert all web tests to BrowserTestBase or UnitTestBase or KernelTestBase and deprecate WebTestBase.
Proposed resolution
Open child issues to convert web tests for each core module. While doing so we should also check if the test cases actually require a browser or can be converted to unit/kernel tests.
Remaining tasks
Convert web tests in child issues.
User interface changes
None.
API changes
WebTestBase will be deprecated.
Data model changes
None.