Hi, I adjusted the range of the arguments, so it should all work fine now, also, why do you think that test case is invalid? (-2 + 658) > 4, so only -2 is counted

Let me speak to the translator :)

Your Problem is, that you take every 2nd char to Upper. But this is not, what is said in the description. There it is said: "For every second char do a switch of the case."
That means: Lower -> Upper and Upper -> Lower!

With that modification your solution works!

(But instead of -= 77 you should generally use the %-Operator.)

Did you read my answer above?

I appear to be having the same issue (as commented elsewhere in this discussion forum). Did you get the issue resolved with the kata author?

The DecryptExampleTests work without problems?

Hi!
Which language? C#?
There are more differences. At index 13 is only the first difference.
Do you have the "-sign in your region?

Maybe past your code here (mark as spoiler!).

Can you provide one clever example of how the task at hand or its solution would change if a different system were used?

You are right but once in a while:-)

I used .net4.0,have no BigInteger Class; int,long,Decimal would be overflow .

string divided into several sections,Calculated each part separately. Then, join them.

In fact， this is a very stupid way.