test(DefaultPageError): add unit tests for dynamic title and error display

Cover all branches of the errors computed property:
- errors[] with items: title 'An error occurred', NcNoteCard with message
- no data: title 'Page not found', description shown, no NcNoteCard
- empty errors[] but error.message present: fallback to singular object

Signed-off-by: Vitor Mattos <1079143+vitormattos@users.noreply.github.com>

Author: vitormattos

src/tests/views/DefaultPageError.spec.ts

@@ -0,0 +1,80 @@
+/*
+ * SPDX-FileCopyrightText: 2026 LibreSign contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import { beforeEach, describe, expect, it, vi, type MockedFunction } from 'vitest'
+import { mount } from '@vue/test-utils'
+
+vi.mock('@nextcloud/initial-state', () => ({
+	loadState: vi.fn((app: string, key: string, defaultValue: unknown) => defaultValue),
+}))
+
+vi.mock('@nextcloud/l10n', () => ({
+	t: vi.fn((_app: string, text: string) => text),
+	isRTL: vi.fn(() => false),
+	getLanguage: vi.fn(() => 'en'),
+	getLocale: vi.fn(() => 'en'),
+}))
+
+vi.mock('@nextcloud/vue/components/NcEmptyContent', () => ({
+	default: {
+		name: 'NcEmptyContent',
+		template: '<div class="nc-empty-content"><slot name="action" /><span class="title">{{ name }}</span><span class="description">{{ description }}</span></div>',
+		props: ['name', 'description'],
+	},
+}))
+vi.mock('@nextcloud/vue/components/NcIconSvgWrapper', () => ({
+	default: { name: 'NcIconSvgWrapper', template: '<span />', props: ['path', 'size'] },
+}))
+vi.mock('@nextcloud/vue/components/NcNoteCard', () => ({
+	default: { name: 'NcNoteCard', template: '<div class="nc-note-card"><slot /></div>', props: ['type'] },
+}))
+
+import DefaultPageError from '../../views/DefaultPageError.vue'
+
+describe('DefaultPageError', () => {
+	let loadState: MockedFunction<typeof import('@nextcloud/initial-state').loadState>
+
+	beforeEach(async () => {
+		const { loadState: ls } = await import('@nextcloud/initial-state')
+		loadState = ls as MockedFunction<typeof import('@nextcloud/initial-state').loadState>
+		loadState.mockImplementation((_app, _key, defaultValue) => defaultValue)
+	})
+
+	it('shows "An error occurred" title and error message when errors are provided via initial state', () => {
+		loadState.mockImplementation((app, key, defaultValue) => {
+			if (app === 'libresign' && key === 'errors') {
+				return [{ message: 'This document is not yours. Log out and use the sign link again.' }]
+			}
+			return defaultValue
+		})
+
+		const wrapper = mount(DefaultPageError)
+
+		expect(wrapper.find('.title').text()).toBe('An error occurred')
+		expect(wrapper.find('.description').text()).toBe('')
+		expect(wrapper.find('.nc-note-card').text()).toContain('This document is not yours. Log out and use the sign link again.')
+	})
+
+	it('shows "Page not found" title and description when no errors are present', () => {
+		const wrapper = mount(DefaultPageError)
+
+		expect(wrapper.find('.title').text()).toBe('Page not found')
+		expect(wrapper.find('.description').text()).toContain('Sorry but the page you are looking for')
+		expect(wrapper.find('.nc-note-card').exists()).toBe(false)
+	})
+
+	it('shows error message from "error" key when "errors" array is empty', () => {
+		loadState.mockImplementation((app, key, defaultValue) => {
+			if (app === 'libresign' && key === 'errors') return []
+			if (app === 'libresign' && key === 'error') return { message: 'Something went wrong' }
+			return defaultValue
+		})
+
+		const wrapper = mount(DefaultPageError)
+
+		expect(wrapper.find('.title').text()).toBe('An error occurred')
+		expect(wrapper.find('.nc-note-card').text()).toContain('Something went wrong')
+	})
+})