Problem/Motivation
#2757007: Convert all book web tests to BrowserTestBase uses a method for this, but I believe it should be added to WebAssert. I've already seen similar implementations in contrib.
Proposed resolution
Add the method to WebAssert.
Remaining tasks
- Agree.
- Decide if this needs a test.
- Search for @todos connected with this issue and update to use new assertions.
User interface changes
API changes
Testing additions.