diff --git a/plugins/interface/components/primitives.test.tsx b/plugins/interface/components/primitives.test.tsx
new file mode 100644
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+++ b/plugins/interface/components/primitives.test.tsx
@@ -0,0 +1,165 @@
+import { describe, expect, it } from 'vitest'
+import { renderToString } from 'hono/jsx/dom/server'
+import { Avatar } from './avatar'
+import { Card } from './card'
+import { Input } from './input/Input'
+import { Label } from './label/Label'
+import { Loader } from './loader/Loader'
+import { Toggle } from './toggle'
+import { cn, getAssetImportTagsFromManifest } from '../utils'
+
+describe('interface primitives', () => {
+    it('merges Tailwind utility classes predictably', () => {
+        expect(cn('px-2 text-sm', false && 'hidden', 'px-4')).toBe(
+            'text-sm px-4'
+        )
+    })
+
+    it('renders avatar initials and image variants', () => {
+        const initialAvatar = renderToString(
+            <Avatar username="outerbase" size="sm" toggled />
+        )
+        expect(initialAvatar).toContain('<button')
+        expect(initialAvatar).toContain('ob-size-sm')
+        expect(initialAvatar).toContain('toggle')
+        expect(initialAvatar).toContain('>O</p>')
+
+        const imageAvatar = renderToString(
+            <Avatar
+                as="a"
+                href="/account"
+                image="/avatar.png"
+                username="Ada Lovelace"
+                size="lg"
+                toggled
+                class="profile-avatar"
+            />
+        )
+        expect(imageAvatar).toContain('<a href="/account"')
+        expect(imageAvatar).toContain('ob-size-lg')
+        expect(imageAvatar).toContain('profile-avatar')
+        expect(imageAvatar).toContain('src="/avatar.png"')
+        expect(imageAvatar).toContain('alt="Ada Lovelace"')
+        expect(imageAvatar).toContain('height="36"')
+    })
+
+    it('renders card element variants without dropping attributes', () => {
+        const card = renderToString(
+            <Card className="custom-card" data-testid="summary">
+                Summary
+            </Card>
+        )
+        expect(card).toContain('<div')
+        expect(card).toContain('btn-secondary')
+        expect(card).toContain('custom-card')
+        expect(card).toContain('data-testid="summary"')
+        expect(card).toContain('>Summary</div>')
+
+        const linkCard = renderToString(
+            <Card as="a" href="/settings" variant="primary">
+                Settings
+            </Card>
+        )
+        expect(linkCard).toContain('<a href="/settings"')
+        expect(linkCard).toContain('btn-primary')
+        expect(linkCard).toContain('>Settings</a>')
+    })
+
+    it('renders labels with conditional required copy', () => {
+        const invalidLabel = renderToString(
+            <Label
+                title="API key"
+                required
+                requiredDescription="required"
+                isValid={false}
+                className="field-label"
+            >
+                <input name="apiKey" />
+            </Label>
+        )
+        expect(invalidLabel).toContain('<label')
+        expect(invalidLabel).toContain('field-label')
+        expect(invalidLabel).toContain('API key')
+        expect(invalidLabel).toContain('required')
+        expect(invalidLabel).toContain('name="apiKey"')
+
+        const validLabel = renderToString(
+            <Label title="Name" required requiredDescription="required" isValid>
+                <input name="name" />
+            </Label>
+        )
+        expect(validLabel).not.toContain('text-ob-destructive')
+    })
+
+    it('renders loader sizing through inline styles', () => {
+        const loader = renderToString(<Loader class="saving" size={32} />)
+        expect(loader).toContain('<svg')
+        expect(loader).toContain('class="saving"')
+        expect(loader).toContain('style="height: 32px; width: 32px"')
+        expect(loader).toContain('<animateTransform')
+        expect(loader).toContain('repeatCount="indefinite"')
+    })
+
+    it('renders toggle size and toggled classes', () => {
+        const toggle = renderToString(
+            <Toggle onClick={() => undefined} size="lg" toggled />
+        )
+        expect(toggle).toContain('<button')
+        expect(toggle).toContain('h-7.5 w-12.5')
+        expect(toggle).toContain('dark:bg-neutral-500')
+        expect(toggle).toContain('translate-x-full')
+
+        const offToggle = renderToString(
+            <Toggle onClick={() => undefined} size="sm" toggled={false} />
+        )
+        expect(offToggle).toContain('h-5.5 w-8.5')
+        expect(offToggle).not.toContain('translate-x-full')
+    })
+
+    it('renders input standalone and decorated variants', () => {
+        const plainInput = renderToString(
+            <Input
+                name="plain"
+                initialValue="hello"
+                isValid={false}
+                onValueChange={undefined}
+                size="lg"
+                className="plain-input"
+            />
+        )
+        expect(plainInput).toContain('<input')
+        expect(plainInput).toContain('name="plain"')
+        expect(plainInput).toContain('value="hello"')
+        expect(plainInput).toContain('text-ob-destructive')
+        expect(plainInput).toContain('ob-size-lg')
+        expect(plainInput).toContain('plain-input')
+
+        const decoratedInput = renderToString(
+            <Input
+                name="amount"
+                initialValue="42"
+                onValueChange={undefined}
+                preText="$"
+                postText="USD"
+                size="sm"
+            />
+        )
+        expect(decoratedInput).toContain('<div')
+        expect(decoratedInput).toContain('ob-size-sm')
+        expect(decoratedInput).toContain('>$</span>')
+        expect(decoratedInput).toContain('value="42"')
+        expect(decoratedInput).toContain('>USD</span>')
+    })
+
+    it('builds manifest import tags for a requested page', async () => {
+        const tags = await getAssetImportTagsFromManifest('template')
+        const html = renderToString(<>{tags}</>)
+
+        expect(html).toContain('src="/assets/template.')
+        expect(html).toContain('src="/assets/vendor.')
+        expect(html).toContain('src="/assets/components.')
+        expect(html).toContain('href="/assets/template.')
+        expect(html).toContain('.css"')
+        expect(html).not.toContain('global')
+    })
+})