Add simple test for the ColorPicker

packages/grafana-ui/src/components/ColorPicker/ColorPicker.test.tsx

+import React from 'react';
+import renderer from 'react-test-renderer';
+import { ColorPicker } from './ColorPicker';
+import { ColorPickerTrigger } from './ColorPickerTrigger';
+
+describe('ColorPicker', () => {
+  it('renders ColorPickerTrigger component by default', () => {
+    expect(
+      renderer.create(<ColorPicker color="#EAB839" onChange={() => {}} />).root.findByType(ColorPickerTrigger)
+    ).toBeTruthy();
+  });
+
+  it('renders custom trigger when supplied', () => {
+    const div = renderer
+      .create(
+        <ColorPicker color="#EAB839" onChange={() => {}}>
+          {() => <div>Custom trigger</div>}
+        </ColorPicker>
+      )
+      .root.findByType('div');
+    expect(div.children[0]).toBe('Custom trigger');
+  });
+});