13_palindromes: add a test case for an even-length palindrome

[Sundwalltanner]

Prerequisites

• I have thoroughly read and understand The Odin Project Contributing Guide
• I have searched the existing issues to ensure this improvement hasn't been suggested before (please have a look through our open issues list to make sure)
• The title of this issue follows the <Location of the improvement>: <Brief description of the improvement> format, e.g. Exercises: Add exercise on XYZ
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Improvement Description

Currently, all valid palindromes in /foundations/13_palindromes/palindromes.spec.js are of odd-length, meaning that if a user comes up with an improperly implemented two-pointer solution, it can still pass all of the current tests, even if it doesn't actually work for a valid even-length palindrome.

Acceptance Criteria

• An improperly implemented solution to 13_palindromes will fail the unit test for a valid even-length palindrome

(Optional) Additional Comments

No response

[CouchofTomato]

Is your proposed solution just to add some tests to capture it?

[Sundwalltanner]

Is your proposed solution just to add some tests to capture it?

Yeah, even just a single test case titled something like "detects even-length palindromes" with the word "abba". Maybe a "detects odd-length palindromes" as well so that at least 1 of each is clearly defined in the test cases in case someone in the future decides to change the strings used in the test cases again and understands that the test cases need to include at least 1 odd-length and 1 even-length valid palindrome.

[mao-sz]

I think we can just change one of the true tests to use an even-lengthed palindromic string. There's nothing conceptually different about the lengths that'd necessitate separate test cases.