add unit tests

tests/helpers/renderWithRouter.tsx

@@ -0,0 +1,12 @@
+import type { ReactElement } from 'react';
+import { MemoryRouter } from 'react-router-dom';
+import { render } from '@testing-library/react';
+
+type RenderWithRouterOptions = {
+    route?: string;
+};
+
+export function renderWithRouter(ui: ReactElement, options: RenderWithRouterOptions = {}) {
+    const { route = '/' } = options;
+    return render(<MemoryRouter initialEntries={[route]}>{ui}</MemoryRouter>);
+}