diff --git a/frontend/src/components/ui/__tests__/ToastContainer.test.js b/frontend/src/components/ui/__tests__/ToastContainer.test.js
new file mode 100644
index 0000000..65fb5db
--- /dev/null
+++ b/frontend/src/components/ui/__tests__/ToastContainer.test.js
@@ -0,0 +1,57 @@
+import { describe, it, expect, beforeEach } from 'vitest'
+import { mount } from '@vue/test-utils'
+import { setActivePinia, createPinia } from 'pinia'
+import { useToastStore } from '../../../stores/toast.js'
+import ToastContainer from '../ToastContainer.vue'
+
+beforeEach(() => {
+  setActivePinia(createPinia())
+})
+
+describe('ToastContainer', () => {
+  it('renders nothing when store.toasts is empty', () => {
+    const wrapper = mount(ToastContainer, {
+      global: {
+        stubs: { AppIcon: true, Teleport: true },
+      },
+    })
+    expect(wrapper.find('[data-test="toast"]').exists()).toBe(false)
+  })
+
+  it('renders one element per toast', () => {
+    const store = useToastStore()
+    store.show('First', 'success', 0)
+    store.show('Second', 'error', 0)
+    const wrapper = mount(ToastContainer, {
+      global: {
+        stubs: { AppIcon: true, Teleport: true },
+      },
+    })
+    expect(wrapper.findAll('[data-test="toast"]').length).toBe(2)
+  })
+
+  it('clicking a toast calls dismiss(id)', async () => {
+    const store = useToastStore()
+    store.show('Click me', 'info', 0)
+    const wrapper = mount(ToastContainer, {
+      global: {
+        stubs: { AppIcon: true, Teleport: true },
+      },
+    })
+    await wrapper.find('[data-test="toast"]').trigger('click')
+    expect(store.toasts.length).toBe(0)
+  })
+
+  it('accent class matches type (success -> bg-green-500)', () => {
+    const store = useToastStore()
+    store.show('Success toast', 'success', 0)
+    const wrapper = mount(ToastContainer, {
+      global: {
+        stubs: { AppIcon: true, Teleport: true },
+      },
+    })
+    const toast = wrapper.find('[data-test="toast"]')
+    const accentBar = toast.find('.bg-green-500')
+    expect(accentBar.exists()).toBe(true)
+  })
+})
diff --git a/frontend/src/stores/__tests__/toast.test.js b/frontend/src/stores/__tests__/toast.test.js
new file mode 100644
index 0000000..e661692
--- /dev/null
+++ b/frontend/src/stores/__tests__/toast.test.js
@@ -0,0 +1,64 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest'
+import { setActivePinia, createPinia } from 'pinia'
+import { useToastStore } from '../toast.js'
+
+beforeEach(() => {
+  setActivePinia(createPinia())
+})
+
+afterEach(() => {
+  vi.useRealTimers()
+})
+
+describe('useToastStore', () => {
+  it('show(msg, type, duration) appends a toast with the given fields', () => {
+    const store = useToastStore()
+    store.show('Hi', 'success', 4000)
+    expect(store.toasts.length).toBe(1)
+    expect(store.toasts[0].message).toBe('Hi')
+    expect(store.toasts[0].type).toBe('success')
+    expect(store.toasts[0].duration).toBe(4000)
+  })
+
+  it('show defaults type to success and duration to 4000', () => {
+    const store = useToastStore()
+    store.show('Hi')
+    expect(store.toasts[0].type).toBe('success')
+    expect(store.toasts[0].duration).toBe(4000)
+  })
+
+  it('auto-dismisses after duration using fake timers', () => {
+    vi.useFakeTimers()
+    const store = useToastStore()
+    store.show('Hi', 'success', 4000)
+    expect(store.toasts.length).toBe(1)
+    vi.advanceTimersByTime(4000)
+    expect(store.toasts.length).toBe(0)
+  })
+
+  it('dismiss(id) removes the toast immediately', () => {
+    const store = useToastStore()
+    store.show('Hi', 'success', 0)
+    const id = store.toasts[0].id
+    store.dismiss(id)
+    expect(store.toasts.length).toBe(0)
+  })
+
+  it('duration=0 disables auto-dismiss', () => {
+    vi.useFakeTimers()
+    const store = useToastStore()
+    store.show('Hi', 'success', 0)
+    vi.advanceTimersByTime(10000)
+    expect(store.toasts.length).toBe(1)
+  })
+
+  it('multiple toasts stack with unique ids', () => {
+    const store = useToastStore()
+    store.show('A')
+    store.show('B')
+    store.show('C')
+    expect(store.toasts.length).toBe(3)
+    const ids = store.toasts.map(t => t.id)
+    expect(new Set(ids).size).toBe(3)
+  })
+})