ReactDOMTestUtils deprecation warnings

Adds a deprecation warning to ReactDOMTestUtils.renderIntoDocument,
which is removed in version 19.

Also backports the deprecation warning for ReactDOMTestUtils.act.

packages/react-dom/src/__tests__/ReactDOMHydrationDiff-test.js

@@ -16,6 +16,8 @@ let usingPartialRenderer;
 const util = require('util');
 const realConsoleError = console.error;
 
+const shouldIgnoreConsoleError = require('../../../../scripts/jest/shouldIgnoreConsoleError');
+
 describe('ReactDOMServerHydration', () => {
   let container;
 
@@ -57,6 +59,9 @@ describe('ReactDOMServerHydration', () => {
       // We only want console errors in this suite.
       return null;
     }
+    if (shouldIgnoreConsoleError(format, ...rest)) {
+      return null;
+    }
     rest[rest.length - 1] = normalizeCodeLocInfo(rest[rest.length - 1]);
     return util.format(format, ...rest);
   }

packages/react-dom/src/__tests__/ReactTestUtilsAct-test.js

@@ -493,8 +493,11 @@ function runActTests(label, render, unmount, rerender) {
         // it's annoying that we have to wait a tick before this warning comes in
         await sleep(0);
         if (__DEV__) {
-          expect(console.error.calls.count()).toEqual(1);
+          expect(console.error.calls.count()).toEqual(2);
           expect(console.error.calls.argsFor(0)[0]).toMatch(
+            '`ReactDOMTestUtils.act` is deprecated ',
+          );
+          expect(console.error.calls.argsFor(1)[0]).toMatch(
             'You called act(async () => ...) without await.',
           );
         }
@@ -516,13 +519,16 @@ function runActTests(label, render, unmount, rerender) {
 
         await sleep(150);
         if (__DEV__) {
-          expect(console.error).toHaveBeenCalledTimes(2);
+          expect(console.error).toHaveBeenCalledTimes(3);
           expect(console.error.calls.argsFor(0)[0]).toMatch(
-            'You seem to have overlapping act() calls',
+            '`ReactDOMTestUtils.act` is deprecated ',
           );
           expect(console.error.calls.argsFor(1)[0]).toMatch(
             'You seem to have overlapping act() calls',
           );
+          expect(console.error.calls.argsFor(2)[0]).toMatch(
+            'You seem to have overlapping act() calls',
+          );
         }
       });
 

packages/react-dom/src/test-utils/ReactTestUtils.js

@@ -34,7 +34,7 @@ const getFiberCurrentPropsFromNode = EventInternals[2];
 const enqueueStateRestore = EventInternals[3];
 const restoreStateIfNeeded = EventInternals[4];
 
-const act = React.unstable_act;
+const reactAct = React.unstable_act;
 
 function Event(suffix) {}
 
@@ -121,7 +121,23 @@ function validateClassInstance(inst, methodName) {
  * utilities will suffice for testing purposes.
  * @lends ReactTestUtils
  */
+
+let didWarnAboutReactTestUtilsDeprecation = false;
+
 function renderIntoDocument(element) {
+  if (__DEV__) {
+    if (!didWarnAboutReactTestUtilsDeprecation) {
+      didWarnAboutReactTestUtilsDeprecation = true;
+      console.error(
+        'ReactDOMTestUtils is deprecated and will be removed in a future ' +
+          'major release, because it exposes internal implementation details ' +
+          'that are highly likely to change between releases. Upgrade to a ' +
+          'modern testing library, such as @testing-library/react. See ' +
+          'https://react.dev/warnings/react-dom-test-utils for more info.',
+      );
+    }
+  }
+
   const div = document.createElement('div');
   // None of our tests actually require attaching the container to the
   // DOM, and doing so creates a mess that we rely on test isolation to
@@ -711,6 +727,23 @@ function buildSimulators() {
 }
 buildSimulators();
 
+let didWarnAboutUsingAct = false;
+export const act = __DEV__
+  ? function actWithWarning(callback) {
+      if (__DEV__) {
+        if (!didWarnAboutUsingAct) {
+          didWarnAboutUsingAct = true;
+          console.error(
+            '`ReactDOMTestUtils.act` is deprecated in favor of `React.act`. ' +
+              'Import `act` from `react` instead of `react-dom/test-utils`. ' +
+              'See https://react.dev/warnings/react-dom-test-utils for more info.',
+          );
+        }
+      }
+      return reactAct(callback);
+    }
+  : reactAct;
+
 export {
   renderIntoDocument,
   isElement,
@@ -729,5 +762,4 @@ export {
   mockComponent,
   nativeTouchData,
   Simulate,
-  act,
 };

scripts/jest/shouldIgnoreConsoleError.js

@@ -29,7 +29,9 @@ module.exports = function shouldIgnoreConsoleError(format, args) {
         ) !== -1 ||
         format.indexOf(
           'uses the legacy childContextTypes API which is no longer supported and will be removed'
-        ) !== -1
+        ) !== -1 ||
+        format.indexOf('ReactDOMTestUtils is deprecated') !== -1 ||
+        format.indexOf('`ReactDOMTestUtils.act` is deprecated') !== -1
       ) {
         // This is a backported warning. In `main`, there's a different warning
         // (and it's fully tested). Not going to bother upgrading all the tests