Fixing "act(...) wraps test-utils" in React Router v6

If you’ve upgraded to React Router v6 and started seeing this warning in your tests, it’s almost always one missing wrapper.

The warning

Warning: An update to App inside a test was not wrapped in act(...).

The cause

React Router’s navigation triggers state updates outside of the render you’re directly testing, and render() from @testing-library/react doesn’t automatically wrap router-driven updates in act().

The fix

Wrap renders that trigger navigation in await act(async () => { ... }), or — cleaner — use findBy* queries instead of getBy* right after a navigation, since they wait for the next tick:

test("navigates to dashboard", async () => {
  render(<App />, { wrapper: MemoryRouterWrapper });
  fireEvent.click(screen.getByText("Login"));
  expect(await screen.findByText("Dashboard")).toBeInTheDocument();
});

That single change — swapping getByText for await screen.findByText after any action that triggers routing — made the warning disappear across the whole test suite.