Add unit test for ToggleThemeButton

Author: fzaninotto

packages/ra-ui-materialui/src/button/ToggleThemeButton.spec.tsx

@@ -0,0 +1,26 @@
+import * as React from 'react';
+import { render, screen } from '@testing-library/react';
+import expect from 'expect';
+
+import { Basic } from './ToggleThemeButton.stories';
+
+describe('ToggleThemeButton', () => {
+    it('should display a button', () => {
+        render(<Basic />);
+        screen.getByLabelText('Toggle Theme');
+    });
+    it('should allow to change the theme between light and dark', () => {
+        const { container } = render(<Basic />);
+        const root = container.querySelector<HTMLDivElement>(
+            '.MuiScopedCssBaseline-root'
+        );
+        if (!root) {
+            throw new Error('No root element found');
+        }
+        expect(getComputedStyle(root).colorScheme).toBe('light');
+        screen.getByLabelText('Toggle Theme').click();
+        expect(getComputedStyle(root).colorScheme).toBe('dark');
+        screen.getByLabelText('Toggle Theme').click();
+        expect(getComputedStyle(root).colorScheme).toBe('light');
+    });
+});