diff --git a/src/shared/ui/Popover/Popover.svelte.test.ts b/src/shared/ui/Popover/Popover.svelte.test.ts
new file mode 100644
index 0000000..603c7a9
--- /dev/null
+++ b/src/shared/ui/Popover/Popover.svelte.test.ts
@@ -0,0 +1,49 @@
+import {
+    fireEvent,
+    render,
+    screen,
+} from '@testing-library/svelte';
+import Harness from './PopoverHarness.svelte';
+
+/**
+ * Resolve the popover content element (the [popover] ancestor of the test content).
+ */
+function getContent(): HTMLElement {
+    return screen.getByTestId('content').closest('[popover]') as HTMLElement;
+}
+
+describe('Popover', () => {
+    it('renders the trigger with aria wiring, closed by default', () => {
+        render(Harness);
+        const trigger = screen.getByRole('button', { name: 'Open' });
+        expect(trigger).toHaveAttribute('aria-expanded', 'false');
+        expect(trigger).toHaveAttribute('aria-haspopup', 'dialog');
+        expect(trigger).toHaveAttribute('popovertarget');
+        expect(getContent()).toHaveAttribute('data-state', 'closed');
+    });
+
+    it('opens via the popover toggle and syncs aria-expanded + data-state', async () => {
+        render(Harness);
+        const trigger = screen.getByRole('button', { name: 'Open' });
+        // jsdom does not auto-invoke popovertarget; call the API the browser would.
+        getContent().showPopover();
+        await Promise.resolve();
+        expect(getContent()).toHaveAttribute('data-state', 'open');
+        expect(trigger).toHaveAttribute('aria-expanded', 'true');
+    });
+
+    it('opens when the parent sets open=true (state -> browser)', async () => {
+        render(Harness, { open: true });
+        await Promise.resolve();
+        expect(getContent()).toHaveAttribute('data-state', 'open');
+    });
+
+    it('close() hides the popover and resets aria-expanded', async () => {
+        render(Harness, { open: true });
+        await Promise.resolve();
+        const trigger = screen.getByRole('button', { name: 'Open' });
+        await fireEvent.click(screen.getByTestId('close'));
+        expect(getContent()).toHaveAttribute('data-state', 'closed');
+        expect(trigger).toHaveAttribute('aria-expanded', 'false');
+    });
+});
diff --git a/src/shared/ui/Popover/PopoverHarness.svelte b/src/shared/ui/Popover/PopoverHarness.svelte
new file mode 100644
index 0000000..566e154
--- /dev/null
+++ b/src/shared/ui/Popover/PopoverHarness.svelte
@@ -0,0 +1,21 @@
+<!--
+    Component: PopoverHarness
+    Test-only fixture: renders Popover with a button trigger and simple content
+    exposing the close() callback.
+-->
+<script lang="ts">
+import Popover from './Popover.svelte';
+
+let { open = $bindable(false) }: { open?: boolean } = $props();
+</script>
+
+<Popover bind:open>
+    {#snippet trigger(props)}
+        <button {...props}>Open</button>
+    {/snippet}
+    {#snippet children({ close })}
+        <div data-testid="content">
+            <button onclick={close} data-testid="close">Close</button>
+        </div>
+    {/snippet}
+</Popover>