test: cover grid filter OR/AND (extract pure fn + unit + real e2e)

The two filter-search cases were test.fixme placeholders (expect(true).toBe(true)),
so the OR/AND chip rules were untested.

- Extract the grid-filter predicate from feed/+page.svelte into a pure
  filterUploads(uploads, filters) in $lib/feed-filter (behavior-preserving) and
  unit-test it (9 cases): tag OR, user OR, tag+user AND, AND-excludes-partial,
  case-insensitive caption match, null caption.
- Replace the e2e fixmes with real tests that seed known captions/uploaders, switch
  to grid view, activate chips via the search suggestions, and count grid tiles:
  OR widens 1→2, AND narrows 2→1.

Frontend unit: 27 passing. filter-search e2e: 3 passing.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/lib/feed-filter.test.ts

@@ -0,0 +1,59 @@
+import { describe, it, expect } from 'vitest';
+import { filterUploads, type FeedFilter } from './feed-filter';
+
+// filterUploads only reads `caption` and `uploader_name`, so a partial shape suffices.
+const u = (id: string, uploader_name: string, caption: string | null) =>
+	({ id, uploader_name, caption }) as any;
+
+const uploads = [
+	u('1', 'Alice', 'pic #wedding'),
+	u('2', 'Bob', 'party #party'),
+	u('3', 'Alice', 'more #wedding #party'),
+	u('4', 'Carol', 'no tags here'),
+	u('5', 'Bob', null), // no caption
+];
+
+const ids = (r: any[]) => r.map((x) => x.id);
+const tag = (value: string): FeedFilter => ({ type: 'tag', value });
+const user = (value: string): FeedFilter => ({ type: 'user', value });
+
+describe('filterUploads', () => {
+	it('no filters → returns all uploads unchanged', () => {
+		expect(filterUploads(uploads, [])).toBe(uploads);
+	});
+
+	it('a single tag matches uploads whose caption contains it', () => {
+		expect(ids(filterUploads(uploads, [tag('wedding')]))).toEqual(['1', '3']);
+	});
+
+	it('two tags combine with OR', () => {
+		expect(ids(filterUploads(uploads, [tag('wedding'), tag('party')]))).toEqual(['1', '2', '3']);
+	});
+
+	it('a single user matches only that uploader', () => {
+		expect(ids(filterUploads(uploads, [user('Alice')]))).toEqual(['1', '3']);
+	});
+
+	it('two users combine with OR', () => {
+		expect(ids(filterUploads(uploads, [user('Alice'), user('Bob')]))).toEqual(['1', '2', '3', '5']);
+	});
+
+	it('a user chip and a tag chip combine with AND', () => {
+		// Alice AND #wedding → only Alice's wedding uploads (not Bob's #wedding, not Alice's #party-only)
+		expect(ids(filterUploads(uploads, [user('Alice'), tag('wedding')]))).toEqual(['1', '3']);
+	});
+
+	it('AND excludes an uploader-match that lacks the tag', () => {
+		// Bob AND #wedding → none (Bob has #party and a null caption, no #wedding)
+		expect(filterUploads(uploads, [user('Bob'), tag('wedding')])).toHaveLength(0);
+	});
+
+	it('tag matching is case-insensitive against the caption', () => {
+		expect(filterUploads([u('9', 'X', 'PIC #WeDDing')], [tag('wedding')])).toHaveLength(1);
+	});
+
+	it('a null caption never matches a tag but can match a user', () => {
+		expect(filterUploads([u('5', 'Bob', null)], [tag('party')])).toHaveLength(0);
+		expect(filterUploads([u('5', 'Bob', null)], [user('Bob')])).toHaveLength(1);
+	});
+});

frontend/src/lib/feed-filter.ts

@@ -0,0 +1,35 @@
+// Grid-view feed filtering. Extracted from feed/+page.svelte so the OR/AND
+// combination rules are unit-testable without mounting the page.
+
+import type { FeedUpload } from './types';
+
+export interface FeedFilter {
+	type: 'tag' | 'user';
+	value: string;
+}
+
+/**
+ * Apply the active grid filters to a list of uploads.
+ *
+ * Combination rules (mirroring the chip UI):
+ *  - Tags combine with **OR**: a card passes the tag group if its caption contains
+ *    ANY selected `#tag`.
+ *  - Users combine with **OR** within the user group (uploader is one of the
+ *    selected names).
+ *  - The tag group and the user group combine with **AND**: a card must satisfy
+ *    both groups. An empty group is a pass-through.
+ *
+ * Tags are matched against the caption text (the autocomplete source), so `value`
+ * is expected lowercase (as produced by the tag suggestions).
+ */
+export function filterUploads(uploads: FeedUpload[], filters: FeedFilter[]): FeedUpload[] {
+	if (filters.length === 0) return uploads;
+	const tags = filters.filter((f) => f.type === 'tag').map((f) => f.value);
+	const users = filters.filter((f) => f.type === 'user').map((f) => f.value);
+	return uploads.filter((u) => {
+		const cap = (u.caption ?? '').toLowerCase();
+		const passTag = !tags.length || tags.some((t) => cap.includes('#' + t));
+		const passUser = !users.length || users.includes(u.uploader_name);
+		return passTag && passUser;
+	});
+}

frontend/src/routes/feed/+page.svelte

@@ -15,6 +15,7 @@
 	import { toast, toastError } from '$lib/toast-store';
 	import { pullToRefresh } from '$lib/actions/pull-to-refresh';
 	import { vibrate } from '$lib/haptics';
+	import { filterUploads } from '$lib/feed-filter';
 	import type { FeedUpload, FeedResponse, HashtagCount, DeltaResponse } from '$lib/types';
 
 	let uploads = $state<FeedUpload[]>([]);
@@ -149,14 +150,7 @@
 	// ── Filtered uploads for grid view ───────────────────────────────────────
 	let displayUploads = $derived.by(() => {
 		if (viewMode === 'list' || activeFilters.length === 0) return uploads;
-		const tags = activeFilters.filter((f) => f.type === 'tag').map((f) => f.value);
-		const users = activeFilters.filter((f) => f.type === 'user').map((f) => f.value);
-		return uploads.filter((u) => {
-			const cap = (u.caption ?? '').toLowerCase();
-			const passTag = !tags.length || tags.some((t) => cap.includes('#' + t));
-			const passUser = !users.length || users.includes(u.uploader_name);
-			return passTag && passUser;
-		});
+		return filterUploads(uploads, activeFilters);
 	});
 
 	// ─────────────────────────────────────────────────────────────────────────