Which is a valid apex assignment?

When are code coverage calculations updated?

While writing an Apex class, a developer wants to make sure that all functionality being developed is handled as specified by the requirements.
Which approach should the developer use to be sure that the Apex class is working according to specifications?

Which three operations affect the number of times a trigger can fire?
Choose 3 answers

A custom Visualforce controller calls the ApexPages,addMessage () method, but no messages are rendering on the page.
Which component should be added to the Visualforce page to display the message?