[Testing] Formatting assertions list

[MrYamous]

On the Testing page we have a list of assertions proposed by Symfony.

I have the impression that the current format isn't the most readable : the difference between explanations and methods/signatures isn't very clear imo.

What do you think of putting this in a block of code to obtain a result similar to this page ?

[javiereguiluz]

I agree with you that the current list doesn't look good.

I'm not sure about which format would work first though. Let's wait for more opinions. Thanks!

[OskarStark]

Would you like to make a proposal for one or two methods and add a screenshot?