Aniket Manna — R51-T038: Cover the failure behavior of doubly linked list (DoublyLinkedList.js) [src/data-structures/doubly-linked-list] #38

Student: Aniket Manna

Task: R51-T038 · 8 of 10
Repository: https://github.com/S-AI-Projects/javascript-algorithms
Assigned working branch: student/e26b07f0860

Goal

Work on src/data-structures/doubly-linked-list/DoublyLinkedList.js. Exercise a documented failure or absent-result branch of doubly linked list. Where the contract is total, use its valid empty/missing-result case instead of inventing an exception. Fixture: Construct three distinct nodes A→B→C and the smallest supported list. Check values and node links separately so a value-only comparison cannot hide a broken link.

Steps

1. Read src/data-structures/doubly-linked-list/DoublyLinkedList.js, especially doubly linked list near line 1. Record its public inputs, result, mutation behavior and any external dependencies before changing it.
2. Locate the actual return, raise, rejection or fallback branch in the source and construct the smallest input reaching it.
3. Assert the intended exception/sentinel and verify that caller-owned state remains valid afterwards; include a successful call after the failure.
4. Implement work/R51-T038/check.py as a focused runner that executes the new checks and propagates failures. Native check to incorporate: run the repository test script in non-watch mode after installing from its lockfile; for browser-only code use a browser test instead of plain Node. Record the actual command and nonzero test count.
5. Create the checks specified below and run python3 work/R51-T038/check.py. Save inputs, expected versus actual results and tool versions in work/R51-T038/; a check must exit non-zero when an assertion fails.
6. Commit the repository change on branch R51-T038; prepare a PR to the organisation fork explaining the result and linking the checks. Keep each task independently reviewable. Remove work/R51-T038/ from a later upstream branch.

Done when

☐ The checked behavior is tied to doubly linked list in src/data-structures/doubly-linked-list/DoublyLinkedList.js; every assertion has an explicit expected value.
☐ Construct three distinct nodes A→B→C and the smallest supported list. Check values and node links separately so a value-only comparison cannot hide a broken link.
☐ Existing supported behavior and the public interface are preserved unless a failing regression demonstrates and documents a defect.
☐ The tested branch is named by source line and the input actually reaches it.
☐ An ordinary valid call still succeeds after the failure case.

Submission checklist

• Complete this task and its checks.
• Add the required evidence and link your pull request here.
• Select this S-AI-Projects fork as the PR base repository.
• Request instructor review.

Keep this PR focused on this task. Do not submit assignment PRs to the upstream repository.