Scala translation

What is the reason to have an empty array as an argument in one the tests when Node isn't even similar to an array?

The context is non-sensical: a tree having children defined as a list should NEVER have anything else than a list for the children property. A leaf is just a node with an empty list. Using None/null/... or anything that isn't a list (or at the very least an iterable, let's say) just implies the initial design is... bad.

So:

• empty nodes must be replaced with empty lists/arrays
• explicit tests with an empty tree must be added as fixed test
• the random tests must be updated and tweaked a bit so that some empty trees will be sent to the user.

Cheers

No random tests

There is already a calculator kata (https://www.codewars.com/kata/calculator, 3 kyu), so it's definitely a duplicate.