Check your very last char!

I really don't understand, why I can't pass the first WhiteSpaceTest,
Input: "1"
Expected: False ???

Please advise!

Me too

Thank you for feedback. English not my natural language and my level must be better.
I happy by any help to doing better my kata. Because it doing this kata pretty for all.

Hi, can you point, what you don't understands?
I would be happy to make the description better.

Const: Maybe to discover some wrong parametrization (a class declared with wrong operator overload, modified the input in that overload, etc) - but, yes, in this simple case, not really applies.

Ref: if you want to avoid a complex object to be copied (an object that overloads * the operator) at every call of square.

You can't avoid recursion withouth avoiding recursion.

You have to discard leading zeros

I would approach this by coming up with all possible numbers within the test range that are consecutive square sums. The first one would be 1^2 + 2^2, then 1^2 + 2^2 + 3^2, and so on.

5, 55, 77, 181,...

Just say it then.

Why do you think it should be invalidated?

i don't see your solution?

Saw your comment and made mine non recursive :)