diff --git a/lib/theming/src/tests/create.test.js b/lib/theming/src/tests/create.test.js
new file mode 100644
index 000000000000..83986ab9cd77
--- /dev/null
+++ b/lib/theming/src/tests/create.test.js
@@ -0,0 +1,109 @@
+import { create } from '../create';
+
+describe('create base', () => {
+  it('should create a theme with minimal viable theme', () => {
+    const result = create({ base: 'light' });
+
+    expect(result).toBeDefined();
+  });
+  it('should pick `light` when `base` is missing', () => {
+    const result = create({ base: undefined });
+
+    expect(result.base).toBe('light');
+  });
+  it('should pick `light` when nothing is given', () => {
+    const result = create();
+
+    expect(result.base).toBe('light');
+  });
+  it('should pick `dark` when base is dark', () => {
+    const result = create({ base: 'dark' });
+
+    expect(result.base).toBe('dark');
+  });
+  it('should pick `light` when base is a unknown value', () => {
+    const result = create({ base: 'foobar' });
+
+    expect(result.base).toBe('light');
+  });
+});
+
+describe('create merge', () => {
+  it('should merge colorPrimary', () => {
+    const result = create({ base: 'light', colorPrimary: 'orange' });
+
+    expect(result.color).toHaveProperty('primary', 'orange');
+  });
+  it('should merge colorSecondary', () => {
+    const result = create({ base: 'light', colorSecondary: 'orange' });
+
+    expect(result.color).toHaveProperty('secondary', 'orange');
+  });
+  it('should merge appBg', () => {
+    const result = create({ base: 'light', appBg: 'orange' });
+
+    expect(result.background).toHaveProperty('app', 'orange');
+  });
+});
+
+describe('create brand', () => {
+  it('should have default', () => {
+    const result = create({ base: 'light' });
+
+    expect(result.brand).toEqual({
+      image: undefined,
+      title: undefined,
+      url: undefined,
+    });
+  });
+  it('should accept null', () => {
+    const result = create({ base: 'light', brandTitle: null, brandUrl: null, brandImage: null });
+
+    expect(result.brand).toEqual({
+      image: null,
+      title: null,
+      url: null,
+    });
+  });
+  it('should accept values', () => {
+    const result = create({
+      base: 'light',
+      brandImage: 'https://placehold.it/350x150',
+      brandTitle: 'my custom storybook',
+      brandUrl: 'https://example.com',
+    });
+
+    expect(result.brand).toEqual({
+      image: 'https://placehold.it/350x150',
+      title: 'my custom storybook',
+      url: 'https://example.com',
+    });
+  });
+});
+
+describe('create extend', () => {
+  it('should allow custom props', () => {
+    const result = create(
+      {
+        base: 'light',
+      },
+      {
+        myCustomProperty: 42,
+      }
+    );
+
+    expect(result.myCustomProperty).toEqual(42);
+  });
+  it('should not allow overriding known properties with custom props', () => {
+    const result = create(
+      {
+        base: 'light',
+      },
+      {
+        base: 42,
+      }
+    );
+
+    expect(result.base).toEqual('light');
+  });
+});