Add assert approx and assert false

[MerlinEgalite]

This PR has been opened to add 2 functionalities:

• assertApproxEq: allows to do testing with an approximation given as input (to avoid small rounding errors).
• assertFalse: The opposite of assertFalse for convenience.

It seems there is a duplicate PR for assertFalse here so we can just merge it and only add the commit for the assertApproxEq from this PR or simply just merge this PR 🙂

Thanks for you feedbacks!

[charlesndalton]

🥇