Run all tests in React strict mode

Author: colinrotherham

src/setupTests.ts

@@ -1,7 +1,10 @@
 import { TextDecoder, TextEncoder } from 'node:util';
 import '@testing-library/jest-dom';
+import { configure } from '@testing-library/react';
 import { outdent } from 'outdent';
 
+configure({ reactStrictMode: true });
+
 /**
  * Polyfill TextEncoder/TextDecoder for ReactDOM
  *

src/util/components/index.ts src/util/components/index.tsxsrc/util/components/index.ts renamed to src/util/components/index.tsx

@@ -1,5 +1,5 @@
 import { render, type RenderOptions as ClientOptions } from '@testing-library/react';
-import { act, type JSX } from 'react';
+import { act, StrictMode, type JSX } from 'react';
 import { renderToString, type ServerOptions } from 'react-dom/server';
 
 type RenderOptions =
@@ -18,7 +18,7 @@ export async function renderServer(element: JSX.Element, options: RenderOptions
   document.body.appendChild(container);
 
   // Render using React DOM
-  container.innerHTML = renderToString(element, serverOptions);
+  container.innerHTML = renderToString(<StrictMode>{element}</StrictMode>, serverOptions);
 
   // Find rendered modules
   const modules = Array.from(container.querySelectorAll<HTMLElement>(selector));