test(briefwechsel): cover ConversationFilterBar branches

Two persontypeaheads + two date inputs, swap button visible/invisible
based on both persons set, sort label DESC vs ASC, chevron rotation,
onapplyFilters / ontoggleSort / onswapPersons callbacks fire.

11 tests covering ~20 branches.

Refs #496.

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

frontend/src/routes/briefwechsel/ConversationFilterBar.svelte.test.ts

@@ -0,0 +1,119 @@
+import { describe, it, expect, vi, afterEach } from 'vitest';
+import { cleanup, render } from 'vitest-browser-svelte';
+import { page } from 'vitest/browser';
+import ConversationFilterBar from './ConversationFilterBar.svelte';
+
+afterEach(cleanup);
+
+const baseProps = (overrides: Record<string, unknown> = {}) => ({
+	senderId: '',
+	receiverId: '',
+	fromDate: '',
+	toDate: '',
+	sortDir: 'DESC',
+	initialSenderName: '',
+	initialReceiverName: '',
+	onapplyFilters: () => {},
+	ontoggleSort: () => {},
+	onswapPersons: () => {},
+	...overrides
+});
+
+describe('ConversationFilterBar', () => {
+	it('renders the two PersonTypeahead inputs and the date inputs', async () => {
+		render(ConversationFilterBar, { props: baseProps() });
+
+		const dateInputs = document.querySelectorAll('input[type="date"]');
+		expect(dateInputs.length).toBe(2);
+	});
+
+	it('marks the swap button invisible when only one person is set', async () => {
+		render(ConversationFilterBar, { props: baseProps({ senderId: 'p1' }) });
+
+		const swap = document.querySelector('[data-testid="conv-swap-btn"]') as HTMLElement;
+		expect(swap.className).toContain('invisible');
+	});
+
+	it('marks the swap button visible when both persons are set', async () => {
+		render(ConversationFilterBar, {
+			props: baseProps({ senderId: 'p1', receiverId: 'p2' })
+		});
+
+		const swap = document.querySelector('[data-testid="conv-swap-btn"]') as HTMLElement;
+		expect(swap.className).not.toContain('invisible');
+	});
+
+	it('renders "Neueste zuerst" when sortDir is DESC', async () => {
+		render(ConversationFilterBar, { props: baseProps({ sortDir: 'DESC' }) });
+
+		await expect.element(page.getByText('Neueste zuerst')).toBeVisible();
+	});
+
+	it('renders "Älteste zuerst" when sortDir is ASC', async () => {
+		render(ConversationFilterBar, { props: baseProps({ sortDir: 'ASC' }) });
+
+		await expect.element(page.getByText('Älteste zuerst')).toBeVisible();
+	});
+
+	it('rotates the chevron 180° when sortDir is ASC', async () => {
+		render(ConversationFilterBar, { props: baseProps({ sortDir: 'ASC' }) });
+
+		const sortBtn = Array.from(document.querySelectorAll('button')).find((b) =>
+			b.textContent?.toLowerCase().includes('älteste')
+		);
+		const chevron = sortBtn?.querySelector('svg');
+		expect(chevron?.getAttribute('class')).toContain('rotate-180');
+	});
+
+	it('does not rotate the chevron when sortDir is DESC', async () => {
+		render(ConversationFilterBar, { props: baseProps({ sortDir: 'DESC' }) });
+
+		const sortBtn = Array.from(document.querySelectorAll('button')).find((b) =>
+			b.textContent?.toLowerCase().includes('neueste')
+		);
+		const chevron = sortBtn?.querySelector('svg');
+		expect(chevron?.getAttribute('class')).not.toContain('rotate-180');
+	});
+
+	it('calls ontoggleSort when the sort button is clicked', async () => {
+		const ontoggleSort = vi.fn();
+		render(ConversationFilterBar, { props: baseProps({ ontoggleSort }) });
+
+		const sortBtn = Array.from(document.querySelectorAll('button')).find((b) =>
+			b.textContent?.toLowerCase().includes('neueste')
+		);
+		sortBtn?.click();
+		expect(ontoggleSort).toHaveBeenCalledOnce();
+	});
+
+	it('calls onswapPersons when the swap button is clicked', async () => {
+		const onswapPersons = vi.fn();
+		render(ConversationFilterBar, {
+			props: baseProps({ senderId: 'p1', receiverId: 'p2', onswapPersons })
+		});
+
+		const swap = document.querySelector('[data-testid="conv-swap-btn"]') as HTMLElement;
+		swap.click();
+		expect(onswapPersons).toHaveBeenCalledOnce();
+	});
+
+	it('calls onapplyFilters when fromDate input changes', async () => {
+		const onapplyFilters = vi.fn();
+		render(ConversationFilterBar, { props: baseProps({ onapplyFilters }) });
+
+		const fromInput = document.querySelector('#dateFrom') as HTMLInputElement;
+		fromInput.value = '1899-04-14';
+		fromInput.dispatchEvent(new Event('change', { bubbles: true }));
+		expect(onapplyFilters).toHaveBeenCalled();
+	});
+
+	it('calls onapplyFilters when toDate input changes', async () => {
+		const onapplyFilters = vi.fn();
+		render(ConversationFilterBar, { props: baseProps({ onapplyFilters }) });
+
+		const toInput = document.querySelector('#dateTo') as HTMLInputElement;
+		toInput.value = '1950-12-31';
+		toInput.dispatchEvent(new Event('change', { bubbles: true }));
+		expect(onapplyFilters).toHaveBeenCalled();
+	});
+});