Find ways to improve UX with test API

[AndreyBelym]

Our feedback stats show that our customers have some difficulties with our asynchronous APIs sometimes. We should find a way to make our API easier to use or improve diagnostics to report "missing await" and so on as early as possible.

• Selector filters and expressions (need more examples)
• ClientFunction use cases (need more examples)
• Selector.exists is not used to check existence (Add warning messages when trying to assert Selector/ClientFunction instances #5211)
• Detailed diffs (Adding detailed diffs #5255)
• DOM snapshot property await Selector is used in assertions (Raise warnings when snapshot properties are passed to assertions #5250)
• missing awaits for DOM node snapshots (if branches, working with element text) (Add warnings for missing await when trying to get a snapshot property value #5383)
• the problematic allowUnawaitedPromise option [1]

[github-actions]

This issue has been automatically marked as stale because it has not had any activity for a long period. It will be closed and archived if no further activity occurs. However, we may return to this issue in the future. If it still affects you or you have any additional information regarding it, please leave a comment and we will keep it open.

[github-actions]

We're closing this issue after a prolonged period of inactivity. If it still affects you, please add a comment to this issue with up-to-date information. Thank you.