Move stories and tests inside each component folders

front/src/layout/navbar/__tests__/Navbar.test.tsx

@@ -0,0 +1,17 @@
+import { render } from '@testing-library/react';
+
+import { NavbarOnInsights } from '../__stories__/Navbar.stories';
+
+it('Checks the NavItem renders', () => {
+  const { getByRole } = render(<NavbarOnInsights />);
+
+  expect(getByRole('button', { name: 'Insights' })).toHaveAttribute(
+    'aria-selected',
+    'true',
+  );
+
+  expect(getByRole('button', { name: 'Inbox' })).toHaveAttribute(
+    'aria-selected',
+    'false',
+  );
+});