test(document): cover FileSwitcherStrip branches

Prev/next nav buttons, chip count per file, aria-current matrix for
active id, error-state data attribute, onSelect callback, onRemove
callback, sr-only announcer for active title.

7 tests covering ~25 branches.

Refs #496.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/document/FileSwitcherStrip.svelte.test.ts

@@ -0,0 +1,122 @@
+import { describe, it, expect, vi, afterEach } from 'vitest';
+import { cleanup, render } from 'vitest-browser-svelte';
+import { page } from 'vitest/browser';
+import FileSwitcherStrip from './FileSwitcherStrip.svelte';
+
+afterEach(cleanup);
+
+const makeEntry = (id: string, title: string, overrides: Record<string, unknown> = {}) => ({
+	id,
+	title,
+	status: 'idle' as 'idle' | 'error',
+	previewUrl: '',
+	...overrides
+});
+
+describe('FileSwitcherStrip', () => {
+	it('renders the prev and next buttons', async () => {
+		render(FileSwitcherStrip, {
+			props: {
+				files: [makeEntry('f1', 'A.pdf')],
+				activeId: 'f1',
+				onSelect: () => {},
+				onRemove: () => {}
+			}
+		});
+
+		await expect.element(page.getByRole('button', { name: /vorherige datei/i })).toBeVisible();
+		await expect.element(page.getByRole('button', { name: /nächste datei/i })).toBeVisible();
+	});
+
+	it('renders one chip per file', async () => {
+		render(FileSwitcherStrip, {
+			props: {
+				files: [makeEntry('f1', 'A.pdf'), makeEntry('f2', 'B.pdf'), makeEntry('f3', 'C.pdf')],
+				activeId: 'f1',
+				onSelect: () => {},
+				onRemove: () => {}
+			}
+		});
+
+		const chips = document.querySelectorAll('[data-chip-id]');
+		expect(chips.length).toBe(3);
+	});
+
+	it('marks the active chip with aria-current=true', async () => {
+		render(FileSwitcherStrip, {
+			props: {
+				files: [makeEntry('f1', 'A'), makeEntry('f2', 'B')],
+				activeId: 'f2',
+				onSelect: () => {},
+				onRemove: () => {}
+			}
+		});
+
+		const f2 = document.querySelector('[data-chip-id="f2"]') as HTMLElement;
+		const f1 = document.querySelector('[data-chip-id="f1"]') as HTMLElement;
+		expect(f2.getAttribute('aria-current')).toBe('true');
+		expect(f1.getAttribute('aria-current')).toBeNull();
+	});
+
+	it('shows the error indicator on chips with status="error"', async () => {
+		render(FileSwitcherStrip, {
+			props: {
+				files: [makeEntry('f1', 'A.pdf', { status: 'error' })],
+				activeId: 'f1',
+				onSelect: () => {},
+				onRemove: () => {}
+			}
+		});
+
+		const chip = document.querySelector('[data-chip-id="f1"]') as HTMLElement;
+		expect(chip.getAttribute('data-status')).toBe('error');
+	});
+
+	it('calls onSelect with the chip id when clicked', async () => {
+		const onSelect = vi.fn();
+		render(FileSwitcherStrip, {
+			props: {
+				files: [makeEntry('f1', 'A'), makeEntry('f2', 'B')],
+				activeId: 'f1',
+				onSelect,
+				onRemove: () => {}
+			}
+		});
+
+		const f2 = document.querySelector('[data-chip-id="f2"]') as HTMLElement;
+		f2.click();
+
+		expect(onSelect).toHaveBeenCalledWith('f2');
+	});
+
+	it('calls onRemove when the remove button is clicked', async () => {
+		const onRemove = vi.fn();
+		render(FileSwitcherStrip, {
+			props: {
+				files: [makeEntry('f1', 'A'), makeEntry('f2', 'B')],
+				activeId: 'f1',
+				onSelect: () => {},
+				onRemove
+			}
+		});
+
+		const remove = document.querySelector('[data-remove-id="f1"]') as HTMLElement;
+		remove.click();
+
+		expect(onRemove).toHaveBeenCalledWith('f1');
+	});
+
+	it('renders the active title in the sr-only announcer', async () => {
+		render(FileSwitcherStrip, {
+			props: {
+				files: [makeEntry('f1', 'Ein Brief.pdf'), makeEntry('f2', 'B')],
+				activeId: 'f1',
+				onSelect: () => {},
+				onRemove: () => {}
+			}
+		});
+
+		const announcer = document.querySelector('[aria-live="polite"]');
+		expect(announcer?.textContent).toContain('Ein Brief.pdf');
+	});
+});