test(10-02): add failing EmptyState tests (RED)

- 7 it() blocks covering prop rendering, slot rendering, and size variants
- Tests stub AppIcon via global.stubs to avoid ordering dependency
- All 7 tests fail with module-not-found (EmptyState.vue not yet created)

frontend/src/components/ui/__tests__/EmptyState.test.js

@@ -0,0 +1,80 @@
+import { describe, it, expect } from 'vitest'
+import { mount } from '@vue/test-utils'
+import EmptyState from '../EmptyState.vue'
+
+describe('EmptyState', () => {
+  it('renders headline text from the headline prop', () => {
+    const w = mount(EmptyState, {
+      props: { headline: 'Nothing here' },
+      global: { stubs: { AppIcon: true } },
+    })
+    expect(w.text()).toContain('Nothing here')
+  })
+
+  it('renders subtext when provided; omits when empty', () => {
+    const w = mount(EmptyState, {
+      props: { headline: 'Title', subtext: 'hello' },
+      global: { stubs: { AppIcon: true } },
+    })
+    expect(w.text()).toContain('hello')
+
+    const w2 = mount(EmptyState, {
+      props: { headline: 'Title' },
+      global: { stubs: { AppIcon: true } },
+    })
+    const paragraphs = w2.findAll('p')
+    expect(paragraphs.length).toBe(1)
+  })
+
+  it('renders AppIcon when icon prop is set; renders no icon when null', () => {
+    const w = mount(EmptyState, {
+      props: { headline: 'Title', icon: 'folder' },
+      global: { stubs: { AppIcon: true } },
+    })
+    expect(w.findComponent({ name: 'AppIcon' }).exists()).toBe(true)
+
+    const w2 = mount(EmptyState, {
+      props: { headline: 'Title', icon: null },
+      global: { stubs: { AppIcon: true } },
+    })
+    expect(w2.findComponent({ name: 'AppIcon' }).exists()).toBe(false)
+  })
+
+  it('renders nothing in the CTA area when #cta slot is empty', () => {
+    const w = mount(EmptyState, {
+      props: { headline: 'Title' },
+      global: { stubs: { AppIcon: true } },
+    })
+    expect(w.find('button').exists()).toBe(false)
+    expect(w.find('a').exists()).toBe(false)
+  })
+
+  it('renders the #cta slot content when provided', () => {
+    const w = mount(EmptyState, {
+      props: { headline: 'Title' },
+      slots: { cta: '<button data-test="cta-btn">Upload</button>' },
+      global: { stubs: { AppIcon: true } },
+    })
+    expect(w.find('[data-test="cta-btn"]').exists()).toBe(true)
+  })
+
+  it("size='sm' applies the sidebar micro layout (flex container with gap-2)", () => {
+    const w = mount(EmptyState, {
+      props: { headline: 'No folders yet', size: 'sm' },
+      global: { stubs: { AppIcon: true } },
+    })
+    const root = w.element
+    expect(root.classList.contains('flex')).toBe(true)
+    expect(root.classList.contains('gap-2')).toBe(true)
+  })
+
+  it('default size (md) applies the centered layout (text-center py-10)', () => {
+    const w = mount(EmptyState, {
+      props: { headline: 'Nothing here' },
+      global: { stubs: { AppIcon: true } },
+    })
+    const root = w.element
+    expect(root.classList.contains('text-center')).toBe(true)
+    expect(root.classList.contains('py-10')).toBe(true)
+  })
+})