Feature Spec: Article Favorites (REST + GraphQL) test coverage

[devin-ai-integration]

Feature Spec: Article Favorites

As a registered user, I can favorite and unfavorite articles so I can curate a reading list, and any client can see accurate favorite state and counts. This spec covers the REST endpoints, the GraphQL mutations, and the favorite read-model behavior.

Behavior / Acceptance Criteria

Favorite an article (REST POST /articles/{slug}/favorite)

• AC1: An authenticated user favoriting an existing article receives 200 and the returned article.favorited is true.
• AC2: The returned article.favoritesCount reflects the article's favorite count including this user.
• AC3: Favoriting an article that does not exist returns 404.
• AC4: An unauthenticated request returns 401 and does not change favorite state.
• AC5: Favoriting an article the user has already favorited is idempotent — still 200, favorited=true, and the count is not double-incremented.

Unfavorite an article (REST DELETE /articles/{slug}/favorite)

• AC6: An authenticated user unfavoriting a previously favorited article receives 200 and article.favorited is false.
• AC7: article.favoritesCount decreases accordingly after unfavoriting.
• AC8: Unfavoriting an article that does not exist returns 404.
• AC9: An unauthenticated request returns 401.
• AC10: Unfavoriting an article the user had not favorited is a no-op — 200, favorited=false, count unchanged.

GraphQL parity

• AC11: The favoriteArticle(slug) mutation sets favorited=true and returns the updated favoritesCount, matching the REST result for the same user/article.
• AC12: The unfavoriteArticle(slug) mutation sets favorited=false, matching the REST result.

Read-model / persistence

• AC13: The favorite read model reports the correct favorited flag per (article, viewer) pair — true only for the viewing user's own favorites.
• AC14: The favorites count for an article equals the number of distinct users who have favorited it.

Notes

• Follow the repo's existing test conventions per tier.
• favorited is always relative to the authenticated/viewing user; an anonymous viewer sees favorited=false.