diff --git a/compat/test/browser/Children.test.js b/compat/test/browser/Children.test.jsx
similarity index 100%
rename from compat/test/browser/Children.test.js
rename to compat/test/browser/Children.test.jsx
diff --git a/compat/test/browser/PureComponent.test.js b/compat/test/browser/PureComponent.test.jsx
similarity index 100%
rename from compat/test/browser/PureComponent.test.js
rename to compat/test/browser/PureComponent.test.jsx
diff --git a/compat/test/browser/cloneElement.test.js b/compat/test/browser/cloneElement.test.jsx
similarity index 97%
rename from compat/test/browser/cloneElement.test.js
rename to compat/test/browser/cloneElement.test.jsx
index 924c968c62..8e5c920ab8 100644
--- a/compat/test/browser/cloneElement.test.js
+++ b/compat/test/browser/cloneElement.test.jsx
@@ -1,5 +1,5 @@
 import { createElement as preactH } from 'preact';
-import React, { createElement, render, cloneElement } from 'preact/compat';
+import { createElement, render, cloneElement } from 'preact/compat';
 import { setupScratch, teardown } from '../../../test/_util/helpers';
 
 describe('compat cloneElement', () => {
diff --git a/compat/test/browser/compat.options.test.js b/compat/test/browser/compat.options.test.jsx
similarity index 99%
rename from compat/test/browser/compat.options.test.js
rename to compat/test/browser/compat.options.test.jsx
index 3b3ed87ed8..067805442b 100644
--- a/compat/test/browser/compat.options.test.js
+++ b/compat/test/browser/compat.options.test.jsx
@@ -1,5 +1,5 @@
 import { vnodeSpy, eventSpy } from '../../../test/_util/optionSpies';
-import React, {
+import {
 	createElement,
 	render,
 	Component,
diff --git a/compat/test/browser/component.test.js b/compat/test/browser/component.test.jsx
similarity index 100%
rename from compat/test/browser/component.test.js
rename to compat/test/browser/component.test.jsx
diff --git a/compat/test/browser/componentDidCatch.test.js b/compat/test/browser/componentDidCatch.test.jsx
similarity index 93%
rename from compat/test/browser/componentDidCatch.test.js
rename to compat/test/browser/componentDidCatch.test.jsx
index abfeccae19..075ce30786 100644
--- a/compat/test/browser/componentDidCatch.test.js
+++ b/compat/test/browser/componentDidCatch.test.jsx
@@ -1,4 +1,4 @@
-import React, { render, Component } from 'preact/compat';
+import { createElement, render, Component } from 'preact/compat';
 import { setupScratch, teardown } from '../../../test/_util/helpers';
 import { act } from 'preact/test-utils';
 
diff --git a/compat/test/browser/context.test.js b/compat/test/browser/context.test.jsx
similarity index 96%
rename from compat/test/browser/context.test.js
rename to compat/test/browser/context.test.jsx
index 35046c88e5..00bf308285 100644
--- a/compat/test/browser/context.test.js
+++ b/compat/test/browser/context.test.jsx
@@ -1,8 +1,9 @@
 import { setupRerender } from 'preact/test-utils';
 import { setupScratch, teardown } from '../../../test/_util/helpers';
-import React, {
+import {
 	render,
 	createElement,
+	Fragment,
 	createContext,
 	Component,
 	useState,
@@ -45,7 +46,7 @@ describe('components', () => {
 		}
 
 		/**
-		 * @extends {React.Component<{children: any}, {location: string}>}
+		 * @extends {Component<{children: any}, {location: string}>}
 		 */
 		class Router extends Component {
 			constructor(props) {
@@ -70,7 +71,7 @@ describe('components', () => {
 		}
 
 		/**
-		 * @extends {React.Component<{children: any}>}
+		 * @extends {Component<{children: any}>}
 		 */
 		class Route extends Component {
 			render() {
diff --git a/compat/test/browser/createElement.test.js b/compat/test/browser/createElement.test.jsx
similarity index 95%
rename from compat/test/browser/createElement.test.js
rename to compat/test/browser/createElement.test.jsx
index 97e948635c..4eeb1f5156 100644
--- a/compat/test/browser/createElement.test.js
+++ b/compat/test/browser/createElement.test.jsx
@@ -1,4 +1,4 @@
-import React, { createElement, render } from 'preact/compat';
+import { createElement, render } from 'preact/compat';
 import { setupScratch, teardown } from '../../../test/_util/helpers';
 import { getSymbol } from './testUtils';
 
diff --git a/compat/test/browser/createFactory.test.js b/compat/test/browser/createFactory.test.jsx
similarity index 89%
rename from compat/test/browser/createFactory.test.js
rename to compat/test/browser/createFactory.test.jsx
index 8d4f929465..6769fa7c91 100644
--- a/compat/test/browser/createFactory.test.js
+++ b/compat/test/browser/createFactory.test.jsx
@@ -1,4 +1,4 @@
-import React, { render, createElement, createFactory } from 'preact/compat';
+import { render, createElement, createFactory } from 'preact/compat';
 import { setupScratch, teardown } from '../../../test/_util/helpers';
 
 describe('createFactory', () => {
diff --git a/compat/test/browser/events.test.js b/compat/test/browser/events.test.jsx
similarity index 99%
rename from compat/test/browser/events.test.js
rename to compat/test/browser/events.test.jsx
index 9ec78b3757..92fa1166b6 100644
--- a/compat/test/browser/events.test.js
+++ b/compat/test/browser/events.test.jsx
@@ -6,7 +6,7 @@ import {
 	supportsPassiveEvents
 } from '../../../test/_util/helpers';
 
-import React, { createElement } from 'preact/compat';
+import { createElement } from 'preact/compat';
 import { vi } from 'vitest';
 
 describe('preact/compat events', () => {
diff --git a/compat/test/browser/findDOMNode.test.js b/compat/test/browser/findDOMNode.test.jsx
similarity index 100%
rename from compat/test/browser/findDOMNode.test.js
rename to compat/test/browser/findDOMNode.test.jsx
diff --git a/compat/test/browser/forwardRef.test.js b/compat/test/browser/forwardRef.test.jsx
similarity index 99%
rename from compat/test/browser/forwardRef.test.js
rename to compat/test/browser/forwardRef.test.jsx
index 259eb7f989..0a3578ca94 100644
--- a/compat/test/browser/forwardRef.test.js
+++ b/compat/test/browser/forwardRef.test.jsx
@@ -1,4 +1,4 @@
-import React, {
+import {
 	createElement,
 	render,
 	createRef,
diff --git a/compat/test/browser/hooks.test.js b/compat/test/browser/hooks.test.jsx
similarity index 99%
rename from compat/test/browser/hooks.test.js
rename to compat/test/browser/hooks.test.jsx
index d6d08adeeb..f984a7b382 100644
--- a/compat/test/browser/hooks.test.js
+++ b/compat/test/browser/hooks.test.jsx
@@ -1,5 +1,5 @@
 import { createContext } from 'preact';
-import React, {
+import {
 	createElement,
 	useDeferredValue,
 	useInsertionEffect,
diff --git a/compat/test/browser/hydrate.test.js b/compat/test/browser/hydrate.test.jsx
similarity index 93%
rename from compat/test/browser/hydrate.test.js
rename to compat/test/browser/hydrate.test.jsx
index a11d3d38b4..25706d0870 100644
--- a/compat/test/browser/hydrate.test.js
+++ b/compat/test/browser/hydrate.test.jsx
@@ -1,4 +1,4 @@
-import React, { hydrate } from 'preact/compat';
+import { createElement, hydrate } from 'preact/compat';
 import { setupScratch, teardown } from '../../../test/_util/helpers';
 import { vi } from 'vitest';
 
diff --git a/compat/test/browser/isMemo.test.js b/compat/test/browser/isMemo.test.jsx
similarity index 100%
rename from compat/test/browser/isMemo.test.js
rename to compat/test/browser/isMemo.test.jsx
diff --git a/compat/test/browser/memo.test.js b/compat/test/browser/memo.test.jsx
similarity index 100%
rename from compat/test/browser/memo.test.js
rename to compat/test/browser/memo.test.jsx
diff --git a/compat/test/browser/portals.test.js b/compat/test/browser/portals.test.jsx
similarity index 100%
rename from compat/test/browser/portals.test.js
rename to compat/test/browser/portals.test.jsx
diff --git a/compat/test/browser/render.test.js b/compat/test/browser/render.test.jsx
similarity index 100%
rename from compat/test/browser/render.test.js
rename to compat/test/browser/render.test.jsx
diff --git a/compat/test/browser/select.test.js b/compat/test/browser/select.test.jsx
similarity index 92%
rename from compat/test/browser/select.test.js
rename to compat/test/browser/select.test.jsx
index bf8c9b97ee..318eadb9b6 100644
--- a/compat/test/browser/select.test.js
+++ b/compat/test/browser/select.test.jsx
@@ -1,5 +1,5 @@
 import { setupScratch, teardown } from '../../../test/_util/helpers';
-import React, { createElement, render } from 'preact/compat';
+import { createElement, render } from 'preact/compat';
 
 describe('Select', () => {
 	let scratch;
diff --git a/compat/test/browser/suspense-hydration.test.js b/compat/test/browser/suspense-hydration.test.jsx
similarity index 100%
rename from compat/test/browser/suspense-hydration.test.js
rename to compat/test/browser/suspense-hydration.test.jsx
diff --git a/compat/test/browser/suspense.test.js b/compat/test/browser/suspense.test.jsx
similarity index 100%
rename from compat/test/browser/suspense.test.js
rename to compat/test/browser/suspense.test.jsx
diff --git a/compat/test/browser/svg.test.js b/compat/test/browser/svg.test.jsx
similarity index 100%
rename from compat/test/browser/svg.test.js
rename to compat/test/browser/svg.test.jsx
diff --git a/compat/test/browser/textarea.test.js b/compat/test/browser/textarea.test.jsx
similarity index 96%
rename from compat/test/browser/textarea.test.js
rename to compat/test/browser/textarea.test.jsx
index d7306a0a40..8a7df4b31b 100644
--- a/compat/test/browser/textarea.test.js
+++ b/compat/test/browser/textarea.test.jsx
@@ -1,4 +1,4 @@
-import React, { render, hydrate, useState } from 'preact/compat';
+import React, { createElement, render, hydrate, useState } from 'preact/compat';
 import ReactDOMServer from 'preact/compat/server';
 import { setupScratch, teardown } from '../../../test/_util/helpers';
 import { act } from 'preact/test-utils';
diff --git a/compat/test/browser/unmountComponentAtNode.test.js b/compat/test/browser/unmountComponentAtNode.test.jsx
similarity index 100%
rename from compat/test/browser/unmountComponentAtNode.test.js
rename to compat/test/browser/unmountComponentAtNode.test.jsx
diff --git a/compat/test/browser/useSyncExternalStore.test.js b/compat/test/browser/useSyncExternalStore.test.jsx
similarity index 100%
rename from compat/test/browser/useSyncExternalStore.test.js
rename to compat/test/browser/useSyncExternalStore.test.jsx
diff --git a/debug/test/browser/component-stack-2.test.js b/debug/test/browser/component-stack-2.test.jsx
similarity index 97%
rename from debug/test/browser/component-stack-2.test.js
rename to debug/test/browser/component-stack-2.test.jsx
index 0cf88d1a9c..aa2634f7a1 100644
--- a/debug/test/browser/component-stack-2.test.js
+++ b/debug/test/browser/component-stack-2.test.jsx
@@ -3,8 +3,6 @@ import 'preact/debug';
 import { setupScratch, teardown } from '../../../test/_util/helpers';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 // This test is not part of component-stack.test.js to avoid it being
 // transpiled with '@babel/plugin-transform-react-jsx-source' enabled.
 
diff --git a/debug/test/browser/component-stack.test.js b/debug/test/browser/component-stack.test.jsx
similarity index 98%
rename from debug/test/browser/component-stack.test.js
rename to debug/test/browser/component-stack.test.jsx
index 5486566c17..8473203362 100644
--- a/debug/test/browser/component-stack.test.js
+++ b/debug/test/browser/component-stack.test.jsx
@@ -3,8 +3,6 @@ import 'preact/debug';
 import { vi } from 'vitest';
 import { setupScratch, teardown } from '../../../test/_util/helpers';
 
-/** @jsx createElement */
-
 describe('component stack', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/debug/test/browser/debug-compat.test.js b/debug/test/browser/debug-compat.test.jsx
similarity index 98%
rename from debug/test/browser/debug-compat.test.js
rename to debug/test/browser/debug-compat.test.jsx
index 244e61f9d2..9394aa384c 100644
--- a/debug/test/browser/debug-compat.test.js
+++ b/debug/test/browser/debug-compat.test.jsx
@@ -10,7 +10,6 @@ import { forwardRef, createPortal } from 'preact/compat';
 import { vi } from 'vitest';
 
 const h = createElement;
-/** @jsx createElement */
 
 describe('debug compat', () => {
 	let scratch;
diff --git a/debug/test/browser/debug-hooks.test.js b/debug/test/browser/debug-hooks.test.jsx
similarity index 98%
rename from debug/test/browser/debug-hooks.test.js
rename to debug/test/browser/debug-hooks.test.jsx
index 698bc430d0..a34fc53a3e 100644
--- a/debug/test/browser/debug-hooks.test.js
+++ b/debug/test/browser/debug-hooks.test.jsx
@@ -5,8 +5,6 @@ import { act } from 'preact/test-utils';
 import { setupScratch, teardown } from '../../../test/_util/helpers';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('debug with hooks', () => {
 	let scratch;
 	let errors = [];
diff --git a/debug/test/browser/debug-suspense.test.js b/debug/test/browser/debug-suspense.test.jsx
similarity index 99%
rename from debug/test/browser/debug-suspense.test.js
rename to debug/test/browser/debug-suspense.test.jsx
index 2368beb482..18c7c53e19 100644
--- a/debug/test/browser/debug-suspense.test.js
+++ b/debug/test/browser/debug-suspense.test.jsx
@@ -8,8 +8,6 @@ import {
 } from '../../../test/_util/helpers';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('debug with suspense', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/debug/test/browser/debug.options.test.js b/debug/test/browser/debug.options.test.jsx
similarity index 99%
rename from debug/test/browser/debug.options.test.js
rename to debug/test/browser/debug.options.test.jsx
index 6c8f9eed9f..6d5ddb8c99 100644
--- a/debug/test/browser/debug.options.test.js
+++ b/debug/test/browser/debug.options.test.jsx
@@ -14,8 +14,6 @@ import 'preact/debug';
 import { setupScratch, teardown } from '../../../test/_util/helpers';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('debug options', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/debug/test/browser/debug.test.js b/debug/test/browser/debug.test.jsx
similarity index 99%
rename from debug/test/browser/debug.test.js
rename to debug/test/browser/debug.test.jsx
index f70434ec93..50cfaad4e1 100644
--- a/debug/test/browser/debug.test.js
+++ b/debug/test/browser/debug.test.jsx
@@ -14,7 +14,6 @@ import { setupRerender } from 'preact/test-utils';
 import { vi } from 'vitest';
 
 const h = createElement;
-/** @jsx createElement */
 
 describe('debug', () => {
 	/** @type {HTMLDivElement} */
diff --git a/debug/test/browser/serializeVNode.test.js b/debug/test/browser/serializeVNode.test.jsx
similarity index 98%
rename from debug/test/browser/serializeVNode.test.js
rename to debug/test/browser/serializeVNode.test.jsx
index f8c851527f..dd04080037 100644
--- a/debug/test/browser/serializeVNode.test.js
+++ b/debug/test/browser/serializeVNode.test.jsx
@@ -1,8 +1,6 @@
 import { createElement, Component } from 'preact';
 import { serializeVNode } from '../../src/debug';
 
-/** @jsx createElement */
-
 describe('serializeVNode', () => {
 	it("should prefer a function component's displayName", () => {
 		function Foo() {
diff --git a/debug/test/browser/validateHookArgs.test.js b/debug/test/browser/validateHookArgs.test.jsx
similarity index 98%
rename from debug/test/browser/validateHookArgs.test.js
rename to debug/test/browser/validateHookArgs.test.jsx
index 1c1b6c9d54..a9af5ed619 100644
--- a/debug/test/browser/validateHookArgs.test.js
+++ b/debug/test/browser/validateHookArgs.test.jsx
@@ -12,8 +12,6 @@ import { setupScratch, teardown } from '../../../test/_util/helpers';
 import 'preact/debug';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('Hook argument validation', () => {
 	/**
 	 * @param {string} name
diff --git a/devtools/test/browser/addHookName.test.js b/devtools/test/browser/addHookName.test.jsx
similarity index 97%
rename from devtools/test/browser/addHookName.test.js
rename to devtools/test/browser/addHookName.test.jsx
index fee3405483..1af4a7620e 100644
--- a/devtools/test/browser/addHookName.test.js
+++ b/devtools/test/browser/addHookName.test.jsx
@@ -4,8 +4,6 @@ import { useState } from 'preact/hooks';
 import { addHookName } from 'preact/devtools';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('addHookName', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/hooks/test/browser/combinations.test.js b/hooks/test/browser/combinations.test.jsx
similarity index 99%
rename from hooks/test/browser/combinations.test.js
rename to hooks/test/browser/combinations.test.jsx
index 3bcb51e986..ed12de26df 100644
--- a/hooks/test/browser/combinations.test.js
+++ b/hooks/test/browser/combinations.test.jsx
@@ -13,8 +13,6 @@ import {
 import { scheduleEffectAssert } from '../_util/useEffectUtil';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('combinations', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/hooks/test/browser/componentDidCatch.test.js b/hooks/test/browser/componentDidCatch.test.jsx
similarity index 97%
rename from hooks/test/browser/componentDidCatch.test.js
rename to hooks/test/browser/componentDidCatch.test.jsx
index bcf8f5c263..4a44f6e79c 100644
--- a/hooks/test/browser/componentDidCatch.test.js
+++ b/hooks/test/browser/componentDidCatch.test.jsx
@@ -3,8 +3,6 @@ import { act } from 'preact/test-utils';
 import { setupScratch, teardown } from '../../../test/_util/helpers';
 import { useEffect } from 'preact/hooks';
 
-/** @jsx createElement */
-
 describe('errorInfo', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/hooks/test/browser/errorBoundary.test.js b/hooks/test/browser/errorBoundary.test.jsx
similarity index 99%
rename from hooks/test/browser/errorBoundary.test.js
rename to hooks/test/browser/errorBoundary.test.jsx
index 366686ec3f..76dc38e411 100644
--- a/hooks/test/browser/errorBoundary.test.js
+++ b/hooks/test/browser/errorBoundary.test.jsx
@@ -4,8 +4,6 @@ import { useErrorBoundary, useLayoutEffect, useState } from 'preact/hooks';
 import { setupRerender } from 'preact/test-utils';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('errorBoundary', () => {
 	/** @type {HTMLDivElement} */
 	let scratch, rerender;
diff --git a/hooks/test/browser/hooks.options.test.js b/hooks/test/browser/hooks.options.test.jsx
similarity index 99%
rename from hooks/test/browser/hooks.options.test.js
rename to hooks/test/browser/hooks.options.test.jsx
index 56924a3644..43fc2527f2 100644
--- a/hooks/test/browser/hooks.options.test.js
+++ b/hooks/test/browser/hooks.options.test.jsx
@@ -22,8 +22,6 @@ import {
 } from 'preact/hooks';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('hook options', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/hooks/test/browser/useCallback.test.js b/hooks/test/browser/useCallback.test.jsx
similarity index 97%
rename from hooks/test/browser/useCallback.test.js
rename to hooks/test/browser/useCallback.test.jsx
index 151fed9af2..0782a9244d 100644
--- a/hooks/test/browser/useCallback.test.js
+++ b/hooks/test/browser/useCallback.test.jsx
@@ -2,8 +2,6 @@ import { createElement, render } from 'preact';
 import { setupScratch, teardown } from '../../../test/_util/helpers';
 import { useCallback } from 'preact/hooks';
 
-/** @jsx createElement */
-
 describe('useCallback', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/hooks/test/browser/useContext.test.js b/hooks/test/browser/useContext.test.jsx
similarity index 99%
rename from hooks/test/browser/useContext.test.js
rename to hooks/test/browser/useContext.test.jsx
index b1f6726c69..473b52ebcd 100644
--- a/hooks/test/browser/useContext.test.js
+++ b/hooks/test/browser/useContext.test.jsx
@@ -4,8 +4,6 @@ import { setupScratch, teardown } from '../../../test/_util/helpers';
 import { useContext, useEffect, useState } from 'preact/hooks';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('useContext', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/hooks/test/browser/useDebugValue.test.js b/hooks/test/browser/useDebugValue.test.jsx
similarity index 98%
rename from hooks/test/browser/useDebugValue.test.js
rename to hooks/test/browser/useDebugValue.test.jsx
index 51e3d162b2..3d0109c352 100644
--- a/hooks/test/browser/useDebugValue.test.js
+++ b/hooks/test/browser/useDebugValue.test.jsx
@@ -3,8 +3,6 @@ import { setupScratch, teardown } from '../../../test/_util/helpers';
 import { useDebugValue, useState } from 'preact/hooks';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('useDebugValue', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/hooks/test/browser/useEffect.test.js b/hooks/test/browser/useEffect.test.jsx
similarity index 99%
rename from hooks/test/browser/useEffect.test.js
rename to hooks/test/browser/useEffect.test.jsx
index f0347b08ba..726cbf6bd9 100644
--- a/hooks/test/browser/useEffect.test.js
+++ b/hooks/test/browser/useEffect.test.jsx
@@ -6,8 +6,6 @@ import { useEffectAssertions } from './useEffectAssertions';
 import { scheduleEffectAssert } from '../_util/useEffectUtil';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('useEffect', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/hooks/test/browser/useEffectAssertions.js b/hooks/test/browser/useEffectAssertions.jsx
similarity index 99%
rename from hooks/test/browser/useEffectAssertions.js
rename to hooks/test/browser/useEffectAssertions.jsx
index 95c87bc2bb..fdb2713601 100644
--- a/hooks/test/browser/useEffectAssertions.js
+++ b/hooks/test/browser/useEffectAssertions.jsx
@@ -3,8 +3,6 @@ import { createElement, render } from 'preact';
 import { setupScratch, teardown } from '../../../test/_util/helpers';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 // Common behaviors between all effect hooks
 export function useEffectAssertions(useEffect, scheduleEffectAssert) {
 	/** @type {HTMLDivElement} */
diff --git a/hooks/test/browser/useId.test.js b/hooks/test/browser/useId.test.jsx
similarity index 99%
rename from hooks/test/browser/useId.test.js
rename to hooks/test/browser/useId.test.jsx
index ff1fa8487d..3697cdff41 100644
--- a/hooks/test/browser/useId.test.js
+++ b/hooks/test/browser/useId.test.jsx
@@ -4,8 +4,6 @@ import { setupRerender } from 'preact/test-utils';
 import { render as rts } from 'preact-render-to-string';
 import { setupScratch, teardown } from '../../../test/_util/helpers';
 
-/** @jsx createElement */
-
 describe('useId', () => {
 	/** @type {HTMLDivElement} */
 	let scratch, rerender;
diff --git a/hooks/test/browser/useImperativeHandle.test.js b/hooks/test/browser/useImperativeHandle.test.jsx
similarity index 99%
rename from hooks/test/browser/useImperativeHandle.test.js
rename to hooks/test/browser/useImperativeHandle.test.jsx
index 36ec351414..feee5b4277 100644
--- a/hooks/test/browser/useImperativeHandle.test.js
+++ b/hooks/test/browser/useImperativeHandle.test.jsx
@@ -4,8 +4,6 @@ import { useImperativeHandle, useRef, useState } from 'preact/hooks';
 import { setupRerender } from 'preact/test-utils';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('useImperativeHandle', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/hooks/test/browser/useLayoutEffect.test.js b/hooks/test/browser/useLayoutEffect.test.jsx
similarity index 99%
rename from hooks/test/browser/useLayoutEffect.test.js
rename to hooks/test/browser/useLayoutEffect.test.jsx
index 82fcd2850c..2bc1b53881 100644
--- a/hooks/test/browser/useLayoutEffect.test.js
+++ b/hooks/test/browser/useLayoutEffect.test.jsx
@@ -9,8 +9,6 @@ import { useEffectAssertions } from './useEffectAssertions';
 import { useLayoutEffect, useRef, useState } from 'preact/hooks';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('useLayoutEffect', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/hooks/test/browser/useMemo.test.js b/hooks/test/browser/useMemo.test.jsx
similarity index 99%
rename from hooks/test/browser/useMemo.test.js
rename to hooks/test/browser/useMemo.test.jsx
index 3265b56340..c552156727 100644
--- a/hooks/test/browser/useMemo.test.js
+++ b/hooks/test/browser/useMemo.test.jsx
@@ -4,8 +4,6 @@ import { useMemo, useState } from 'preact/hooks';
 import { act } from 'preact/test-utils';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('useMemo', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/hooks/test/browser/useReducer.test.js b/hooks/test/browser/useReducer.test.jsx
similarity index 99%
rename from hooks/test/browser/useReducer.test.js
rename to hooks/test/browser/useReducer.test.jsx
index 410805b766..c8578bf18a 100644
--- a/hooks/test/browser/useReducer.test.js
+++ b/hooks/test/browser/useReducer.test.jsx
@@ -3,8 +3,6 @@ import { createElement, render, createContext } from 'preact';
 import { setupScratch, teardown } from '../../../test/_util/helpers';
 import { useReducer, useEffect, useContext } from 'preact/hooks';
 
-/** @jsx createElement */
-
 describe('useReducer', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/hooks/test/browser/useRef.test.js b/hooks/test/browser/useRef.test.jsx
similarity index 97%
rename from hooks/test/browser/useRef.test.js
rename to hooks/test/browser/useRef.test.jsx
index 7d7a657292..bbc4293cdc 100644
--- a/hooks/test/browser/useRef.test.js
+++ b/hooks/test/browser/useRef.test.jsx
@@ -2,8 +2,6 @@ import { createElement, render } from 'preact';
 import { setupScratch, teardown } from '../../../test/_util/helpers';
 import { useRef } from 'preact/hooks';
 
-/** @jsx createElement */
-
 describe('useRef', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/hooks/test/browser/useState.test.js b/hooks/test/browser/useState.test.jsx
similarity index 99%
rename from hooks/test/browser/useState.test.js
rename to hooks/test/browser/useState.test.jsx
index 4d391c209d..d37c572dbd 100644
--- a/hooks/test/browser/useState.test.js
+++ b/hooks/test/browser/useState.test.jsx
@@ -4,8 +4,6 @@ import { vi } from 'vitest';
 import { useState, useContext, useEffect } from 'preact/hooks';
 import { setupScratch, teardown } from '../../../test/_util/helpers';
 
-/** @jsx createElement */
-
 describe('useState', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/jsconfig-lint.json b/jsconfig-lint.json
index 8102dbe98d..0658e4649d 100644
--- a/jsconfig-lint.json
+++ b/jsconfig-lint.json
@@ -3,7 +3,7 @@
   "compilerOptions": {
     "skipLibCheck": true,
     "noEmit": true,
-    "typeRoots": ["./node_modules/@types", "./types"]
+    "typeRoots": ["./node_modules/@types", "./node_modules", "./types"]
   },
   "include": [
     "src/**/*",
diff --git a/jsconfig.json b/jsconfig.json
index 1be014c6a6..cc72eb92ea 100644
--- a/jsconfig.json
+++ b/jsconfig.json
@@ -14,7 +14,8 @@
     },
     "target": "es5",
     "noEmit": true,
-    "skipLibCheck": false
+    "skipLibCheck": false,
+    "types": ["vitest/globals"]
   },
   "exclude": ["**/node_modules/**", "**/dist/**", "coverage", "demo"]
 }
diff --git a/test-utils/test/shared/act.test.js b/test-utils/test/shared/act.test.jsx
similarity index 99%
rename from test-utils/test/shared/act.test.js
rename to test-utils/test/shared/act.test.jsx
index fafc60b470..3ff88e3857 100644
--- a/test-utils/test/shared/act.test.js
+++ b/test-utils/test/shared/act.test.jsx
@@ -4,8 +4,6 @@ import { act } from 'preact/test-utils';
 import { setupScratch, teardown } from '../../../test/_util/helpers';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 // IE11 doesn't support `new Event()`
 function createEvent(name) {
 	if (typeof Event == 'function') return new Event(name);
diff --git a/test-utils/test/shared/rerender.test.js b/test-utils/test/shared/rerender.test.jsx
similarity index 98%
rename from test-utils/test/shared/rerender.test.js
rename to test-utils/test/shared/rerender.test.jsx
index 26a9147a4c..beb9372674 100644
--- a/test-utils/test/shared/rerender.test.js
+++ b/test-utils/test/shared/rerender.test.jsx
@@ -2,8 +2,6 @@ import { options, createElement, render, Component } from 'preact';
 import { teardown, setupRerender } from 'preact/test-utils';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('setupRerender & teardown', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/test/_util/helpers.js b/test/_util/helpers.jsx
similarity index 100%
rename from test/_util/helpers.js
rename to test/_util/helpers.jsx
diff --git a/test/browser/cloneElement.test.js b/test/browser/cloneElement.test.jsx
similarity index 99%
rename from test/browser/cloneElement.test.js
rename to test/browser/cloneElement.test.jsx
index fb8d3367c5..e2380cef9c 100644
--- a/test/browser/cloneElement.test.js
+++ b/test/browser/cloneElement.test.jsx
@@ -1,7 +1,5 @@
 import { createElement, cloneElement, createRef } from 'preact';
 
-/** @jsx createElement */
-
 describe('cloneElement', () => {
 	it('should clone components', () => {
 		function Comp() {}
diff --git a/test/browser/components.test.js b/test/browser/components.test.jsx
similarity index 99%
rename from test/browser/components.test.js
rename to test/browser/components.test.jsx
index 84a40e01c0..479bbba12d 100644
--- a/test/browser/components.test.js
+++ b/test/browser/components.test.jsx
@@ -10,7 +10,6 @@ import {
 } from '../_util/helpers';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
 const h = createElement;
 
 function getAttributes(node) {
diff --git a/test/browser/context.test.js b/test/browser/context.test.jsx
similarity index 99%
rename from test/browser/context.test.js
rename to test/browser/context.test.jsx
index d4fa4b3e81..7450288fe5 100644
--- a/test/browser/context.test.js
+++ b/test/browser/context.test.jsx
@@ -2,8 +2,6 @@ import { createElement, render, Component, Fragment } from 'preact';
 import { setupScratch, teardown } from '../_util/helpers';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('context', () => {
 	let scratch;
 
diff --git a/test/browser/createContext.test.js b/test/browser/createContext.test.jsx
similarity index 99%
rename from test/browser/createContext.test.js
rename to test/browser/createContext.test.jsx
index 84090b6dea..92fa44acce 100644
--- a/test/browser/createContext.test.js
+++ b/test/browser/createContext.test.jsx
@@ -9,8 +9,6 @@ import {
 import { setupScratch, teardown } from '../_util/helpers';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('createContext', () => {
 	let scratch;
 	let rerender;
diff --git a/test/browser/customBuiltInElements.test.js b/test/browser/customBuiltInElements.test.jsx
similarity index 96%
rename from test/browser/customBuiltInElements.test.js
rename to test/browser/customBuiltInElements.test.jsx
index d5a9f32bfc..b9e73d27c3 100644
--- a/test/browser/customBuiltInElements.test.js
+++ b/test/browser/customBuiltInElements.test.jsx
@@ -2,8 +2,6 @@ import { createElement, render, Component } from 'preact';
 import { setupScratch, teardown } from '../_util/helpers';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 const runSuite = typeof customElements == 'undefined' ? xdescribe : describe;
 
 runSuite('customised built-in elements', () => {
diff --git a/test/browser/events.test.js b/test/browser/events.test.jsx
similarity index 99%
rename from test/browser/events.test.js
rename to test/browser/events.test.jsx
index 621e99c26e..456b645c51 100644
--- a/test/browser/events.test.js
+++ b/test/browser/events.test.jsx
@@ -6,8 +6,6 @@ import {
 } from '../_util/helpers';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('event handling', () => {
 	let scratch, proto;
 
diff --git a/test/browser/focus.test.js b/test/browser/focus.test.jsx
similarity index 99%
rename from test/browser/focus.test.js
rename to test/browser/focus.test.jsx
index a3b35343ee..23656a0d86 100644
--- a/test/browser/focus.test.js
+++ b/test/browser/focus.test.jsx
@@ -3,7 +3,6 @@ import { createElement, render, Component, Fragment, hydrate } from 'preact';
 import { setupScratch, teardown } from '../_util/helpers';
 import { div, span, input as inputStr, h1, h2 } from '../_util/dom';
 
-/** @jsx createElement */
 /* eslint-disable react/jsx-boolean-value */
 
 describe('focus', () => {
diff --git a/test/browser/fragments.test.js b/test/browser/fragments.test.jsx
similarity index 99%
rename from test/browser/fragments.test.js
rename to test/browser/fragments.test.jsx
index 783adf3b89..946303be8e 100644
--- a/test/browser/fragments.test.js
+++ b/test/browser/fragments.test.jsx
@@ -10,7 +10,6 @@ import { setupScratch, teardown } from '../_util/helpers';
 import { span, div, ul, ol, li, section } from '../_util/dom';
 import { logCall, clearLog, getLog } from '../_util/logCall';
 
-/** @jsx createElement */
 /* eslint-disable react/jsx-boolean-value */
 
 describe('Fragment', () => {
diff --git a/test/browser/getDomSibling.test.js b/test/browser/getDomSibling.test.jsx
similarity index 99%
rename from test/browser/getDomSibling.test.js
rename to test/browser/getDomSibling.test.jsx
index 66a6aa8921..919b28e562 100644
--- a/test/browser/getDomSibling.test.js
+++ b/test/browser/getDomSibling.test.jsx
@@ -2,8 +2,6 @@ import { createElement, render, Fragment } from '../../src/';
 import { getDomSibling } from '../../src/component';
 import { setupScratch, teardown } from '../_util/helpers';
 
-/** @jsx createElement */
-
 describe('getDomSibling', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/test/browser/hydrate.test.js b/test/browser/hydrate.test.jsx
similarity index 99%
rename from test/browser/hydrate.test.js
rename to test/browser/hydrate.test.jsx
index 896ee6f455..9e7a334a92 100644
--- a/test/browser/hydrate.test.js
+++ b/test/browser/hydrate.test.jsx
@@ -12,8 +12,6 @@ import { ul, li, div } from '../_util/dom';
 import { logCall, clearLog, getLog } from '../_util/logCall';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('hydrate()', () => {
 	/** @type {HTMLElement} */
 	let scratch;
diff --git a/test/browser/keys.test.js b/test/browser/keys.test.jsx
similarity index 99%
rename from test/browser/keys.test.js
rename to test/browser/keys.test.jsx
index 3a5594fbf3..3550352242 100644
--- a/test/browser/keys.test.js
+++ b/test/browser/keys.test.jsx
@@ -5,8 +5,6 @@ import { logCall, clearLog, getLog } from '../_util/logCall';
 import { div } from '../_util/dom';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('keys', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/test/browser/lifecycles/componentDidCatch.test.js b/test/browser/lifecycles/componentDidCatch.test.jsx
similarity index 99%
rename from test/browser/lifecycles/componentDidCatch.test.js
rename to test/browser/lifecycles/componentDidCatch.test.jsx
index 4b0349210a..1b80002388 100644
--- a/test/browser/lifecycles/componentDidCatch.test.js
+++ b/test/browser/lifecycles/componentDidCatch.test.jsx
@@ -3,8 +3,6 @@ import { createElement, render, Component, Fragment } from 'preact';
 import { setupScratch, teardown } from '../../_util/helpers';
 import { vi, expect } from 'vitest';
 
-/** @jsx createElement */
-
 describe('Lifecycle methods', () => {
 	/* eslint-disable react/display-name */
 
diff --git a/test/browser/lifecycles/componentDidMount.test.js b/test/browser/lifecycles/componentDidMount.test.jsx
similarity index 98%
rename from test/browser/lifecycles/componentDidMount.test.js
rename to test/browser/lifecycles/componentDidMount.test.jsx
index 52ec460e11..72717ccf59 100644
--- a/test/browser/lifecycles/componentDidMount.test.js
+++ b/test/browser/lifecycles/componentDidMount.test.jsx
@@ -3,8 +3,6 @@ import { setupRerender } from 'preact/test-utils';
 import { setupScratch, teardown } from '../../_util/helpers';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('Lifecycle methods', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/test/browser/lifecycles/componentDidUpdate.test.js b/test/browser/lifecycles/componentDidUpdate.test.jsx
similarity index 99%
rename from test/browser/lifecycles/componentDidUpdate.test.js
rename to test/browser/lifecycles/componentDidUpdate.test.jsx
index 5b0f9e7d5c..b733d4cb95 100644
--- a/test/browser/lifecycles/componentDidUpdate.test.js
+++ b/test/browser/lifecycles/componentDidUpdate.test.jsx
@@ -3,8 +3,6 @@ import { createElement, render, Component } from 'preact';
 import { setupScratch, teardown } from '../../_util/helpers';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('Lifecycle methods', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/test/browser/lifecycles/componentWillMount.test.js b/test/browser/lifecycles/componentWillMount.test.jsx
similarity index 98%
rename from test/browser/lifecycles/componentWillMount.test.js
rename to test/browser/lifecycles/componentWillMount.test.jsx
index 4e85032ee7..a17bb5c429 100644
--- a/test/browser/lifecycles/componentWillMount.test.js
+++ b/test/browser/lifecycles/componentWillMount.test.jsx
@@ -2,8 +2,6 @@ import { createElement, render, Component } from 'preact';
 import { setupRerender } from 'preact/test-utils';
 import { setupScratch, teardown } from '../../_util/helpers';
 
-/** @jsx createElement */
-
 describe('Lifecycle methods', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/test/browser/lifecycles/componentWillReceiveProps.test.js b/test/browser/lifecycles/componentWillReceiveProps.test.jsx
similarity index 99%
rename from test/browser/lifecycles/componentWillReceiveProps.test.js
rename to test/browser/lifecycles/componentWillReceiveProps.test.jsx
index 7c5f7d171a..d65b408d8a 100644
--- a/test/browser/lifecycles/componentWillReceiveProps.test.js
+++ b/test/browser/lifecycles/componentWillReceiveProps.test.jsx
@@ -3,8 +3,6 @@ import { createElement, render, Component } from 'preact';
 import { setupScratch, teardown } from '../../_util/helpers';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('Lifecycle methods', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/test/browser/lifecycles/componentWillUnmount.test.js b/test/browser/lifecycles/componentWillUnmount.test.jsx
similarity index 98%
rename from test/browser/lifecycles/componentWillUnmount.test.js
rename to test/browser/lifecycles/componentWillUnmount.test.jsx
index 5ba6bc08f5..ebd6f44ec1 100644
--- a/test/browser/lifecycles/componentWillUnmount.test.js
+++ b/test/browser/lifecycles/componentWillUnmount.test.jsx
@@ -2,8 +2,6 @@ import { createElement, render, Component } from 'preact';
 import { setupScratch, teardown } from '../../_util/helpers';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('Lifecycle methods', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/test/browser/lifecycles/componentWillUpdate.test.js b/test/browser/lifecycles/componentWillUpdate.test.jsx
similarity index 98%
rename from test/browser/lifecycles/componentWillUpdate.test.js
rename to test/browser/lifecycles/componentWillUpdate.test.jsx
index ec13781e7d..2e328a2ada 100644
--- a/test/browser/lifecycles/componentWillUpdate.test.js
+++ b/test/browser/lifecycles/componentWillUpdate.test.jsx
@@ -3,8 +3,6 @@ import { createElement, render, Component } from 'preact';
 import { setupScratch, teardown } from '../../_util/helpers';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('Lifecycle methods', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/test/browser/lifecycles/getDerivedStateFromError.test.js b/test/browser/lifecycles/getDerivedStateFromError.test.jsx
similarity index 99%
rename from test/browser/lifecycles/getDerivedStateFromError.test.js
rename to test/browser/lifecycles/getDerivedStateFromError.test.jsx
index 541911923c..4c3b7d6118 100644
--- a/test/browser/lifecycles/getDerivedStateFromError.test.js
+++ b/test/browser/lifecycles/getDerivedStateFromError.test.jsx
@@ -3,8 +3,6 @@ import { createElement, render, Component } from 'preact';
 import { setupScratch, teardown } from '../../_util/helpers';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('Lifecycle methods', () => {
 	/* eslint-disable react/display-name */
 
diff --git a/test/browser/lifecycles/getDerivedStateFromProps.test.js b/test/browser/lifecycles/getDerivedStateFromProps.test.jsx
similarity index 99%
rename from test/browser/lifecycles/getDerivedStateFromProps.test.js
rename to test/browser/lifecycles/getDerivedStateFromProps.test.jsx
index 3b199dddc0..1507fa5773 100644
--- a/test/browser/lifecycles/getDerivedStateFromProps.test.js
+++ b/test/browser/lifecycles/getDerivedStateFromProps.test.jsx
@@ -3,8 +3,6 @@ import { createElement, render, Component } from 'preact';
 import { setupScratch, teardown } from '../../_util/helpers';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('Lifecycle methods', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/test/browser/lifecycles/getSnapshotBeforeUpdate.test.js b/test/browser/lifecycles/getSnapshotBeforeUpdate.test.jsx
similarity index 99%
rename from test/browser/lifecycles/getSnapshotBeforeUpdate.test.js
rename to test/browser/lifecycles/getSnapshotBeforeUpdate.test.jsx
index 645424bee9..7504e3600d 100644
--- a/test/browser/lifecycles/getSnapshotBeforeUpdate.test.js
+++ b/test/browser/lifecycles/getSnapshotBeforeUpdate.test.jsx
@@ -2,8 +2,6 @@ import { setupRerender } from 'preact/test-utils';
 import { createElement, render, Component } from 'preact';
 import { setupScratch, teardown } from '../../_util/helpers';
 
-/** @jsx createElement */
-
 describe('Lifecycle methods', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/test/browser/lifecycles/lifecycle.test.js b/test/browser/lifecycles/lifecycle.test.jsx
similarity index 99%
rename from test/browser/lifecycles/lifecycle.test.js
rename to test/browser/lifecycles/lifecycle.test.jsx
index 5c5977330d..165a8a3699 100644
--- a/test/browser/lifecycles/lifecycle.test.js
+++ b/test/browser/lifecycles/lifecycle.test.jsx
@@ -3,8 +3,6 @@ import { createElement, render, Component } from 'preact';
 import { setupScratch, teardown } from '../../_util/helpers';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('Lifecycle methods', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/test/browser/lifecycles/shouldComponentUpdate.test.js b/test/browser/lifecycles/shouldComponentUpdate.test.jsx
similarity index 99%
rename from test/browser/lifecycles/shouldComponentUpdate.test.js
rename to test/browser/lifecycles/shouldComponentUpdate.test.jsx
index a96e6ca630..3ecd7e8ad3 100644
--- a/test/browser/lifecycles/shouldComponentUpdate.test.js
+++ b/test/browser/lifecycles/shouldComponentUpdate.test.jsx
@@ -4,8 +4,6 @@ import { vi } from 'vitest';
 import { setupScratch, teardown } from '../../_util/helpers';
 import { logCall, getLog, clearLog } from '../../_util/logCall';
 
-/** @jsx createElement */
-
 describe('Lifecycle methods', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/test/browser/mathml.test.js b/test/browser/mathml.test.jsx
similarity index 98%
rename from test/browser/mathml.test.js
rename to test/browser/mathml.test.jsx
index 92e2bb6bcf..79439f4016 100644
--- a/test/browser/mathml.test.js
+++ b/test/browser/mathml.test.jsx
@@ -2,8 +2,6 @@ import { createElement, Component, render } from 'preact';
 import { setupRerender } from 'preact/test-utils';
 import { setupScratch, teardown } from '../_util/helpers';
 
-/** @jsx createElement */
-
 describe('mathml', () => {
 	let scratch;
 
diff --git a/test/browser/placeholders.test.js b/test/browser/placeholders.test.jsx
similarity index 99%
rename from test/browser/placeholders.test.js
rename to test/browser/placeholders.test.jsx
index 9571288fe4..f2f5cf3f09 100644
--- a/test/browser/placeholders.test.js
+++ b/test/browser/placeholders.test.jsx
@@ -5,8 +5,6 @@ import { logCall, clearLog, getLog } from '../_util/logCall';
 import { div } from '../_util/dom';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('null placeholders', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/test/browser/refs.test.js b/test/browser/refs.test.jsx
similarity index 99%
rename from test/browser/refs.test.js
rename to test/browser/refs.test.jsx
index 52ec8ab182..5b42406b4f 100644
--- a/test/browser/refs.test.js
+++ b/test/browser/refs.test.jsx
@@ -3,8 +3,6 @@ import { createElement, render, Component, createRef, Fragment } from 'preact';
 import { setupScratch, teardown } from '../_util/helpers';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 // gives call count and argument errors names (otherwise sinon just uses "spy"):
 let spy = (name, ...args) => {
 	let spy = vi.fn(...args);
diff --git a/test/browser/render.test.js b/test/browser/render.test.jsx
similarity index 99%
rename from test/browser/render.test.js
rename to test/browser/render.test.jsx
index f7272a1369..0139661726 100644
--- a/test/browser/render.test.js
+++ b/test/browser/render.test.jsx
@@ -15,8 +15,6 @@ import { clearLog, getLog, logCall } from '../_util/logCall';
 import { useState } from 'preact/hooks';
 import { expect, vi } from 'vitest';
 
-/** @jsx createElement */
-
 function getAttributes(node) {
 	let attrs = {};
 	for (let i = node.attributes.length; i--; ) {
diff --git a/test/browser/select.test.js b/test/browser/select.test.jsx
similarity index 98%
rename from test/browser/select.test.js
rename to test/browser/select.test.jsx
index 74b08ce570..3c1e4aac29 100644
--- a/test/browser/select.test.js
+++ b/test/browser/select.test.jsx
@@ -1,8 +1,6 @@
 import { createElement, render } from 'preact';
 import { setupScratch, teardown } from '../_util/helpers';
 
-/** @jsx createElement */
-
 describe('Select', () => {
 	let scratch;
 
diff --git a/test/browser/spec.test.js b/test/browser/spec.test.jsx
similarity index 98%
rename from test/browser/spec.test.js
rename to test/browser/spec.test.jsx
index 34c2a2ffff..d14800128d 100644
--- a/test/browser/spec.test.js
+++ b/test/browser/spec.test.jsx
@@ -3,8 +3,6 @@ import { createElement, render, Component } from 'preact';
 import { setupScratch, teardown } from '../_util/helpers';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('Component spec', () => {
 	let scratch, rerender;
 
diff --git a/test/browser/style.test.js b/test/browser/style.test.jsx
similarity index 99%
rename from test/browser/style.test.js
rename to test/browser/style.test.jsx
index 6192482a6a..b341407b93 100644
--- a/test/browser/style.test.js
+++ b/test/browser/style.test.jsx
@@ -2,8 +2,6 @@ import { createElement, render } from 'preact';
 import { setupScratch, teardown, sortCss } from '../_util/helpers';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('style attribute', () => {
 	/** @type {HTMLElement} */
 	let scratch;
diff --git a/test/browser/svg.test.js b/test/browser/svg.test.jsx
similarity index 99%
rename from test/browser/svg.test.js
rename to test/browser/svg.test.jsx
index 21c6bfc277..dd5ccb74a2 100644
--- a/test/browser/svg.test.js
+++ b/test/browser/svg.test.jsx
@@ -3,8 +3,6 @@ import { setupRerender } from 'preact/test-utils';
 import { setupScratch, teardown, sortAttributes } from '../_util/helpers';
 import { vi } from 'vitest';
 
-/** @jsx createElement */
-
 describe('svg', () => {
 	let scratch;
 
diff --git a/test/browser/toChildArray.test.js b/test/browser/toChildArray.test.jsx
similarity index 99%
rename from test/browser/toChildArray.test.js
rename to test/browser/toChildArray.test.jsx
index d1cb950992..cf7560f6d1 100644
--- a/test/browser/toChildArray.test.js
+++ b/test/browser/toChildArray.test.jsx
@@ -6,8 +6,6 @@ import {
 	mixedArrayHTML
 } from '../_util/helpers';
 
-/** @jsx createElement */
-
 describe('toChildArray', () => {
 	/** @type {HTMLDivElement} */
 	let scratch;
diff --git a/test/shared/createContext.test.js b/test/shared/createContext.test.jsx
similarity index 97%
rename from test/shared/createContext.test.js
rename to test/shared/createContext.test.jsx
index a7ce72bca9..39f961f070 100644
--- a/test/shared/createContext.test.js
+++ b/test/shared/createContext.test.jsx
@@ -1,7 +1,6 @@
 import { createElement, createContext } from '../../src/index';
 import { expect } from 'chai';
 
-/** @jsx createElement */
 /* eslint-env browser */
 
 describe('createContext', () => {
diff --git a/test/shared/createElement.test.js b/test/shared/createElement.test.jsx
similarity index 99%
rename from test/shared/createElement.test.js
rename to test/shared/createElement.test.jsx
index 449068b6cb..cf4b0ae2a5 100644
--- a/test/shared/createElement.test.js
+++ b/test/shared/createElement.test.jsx
@@ -2,7 +2,6 @@ import { createElement } from '../../src/index';
 import { expect } from 'chai';
 
 const h = createElement;
-/** @jsx createElement */
 /*eslint-env browser */
 
 // const buildVNode = (nodeName, attributes, children=[]) => ({
diff --git a/test/shared/isValidElementTests.js b/test/shared/isValidElementTests.jsx
similarity index 95%
rename from test/shared/isValidElementTests.js
rename to test/shared/isValidElementTests.jsx
index d0e86b50c5..f8b1a04369 100644
--- a/test/shared/isValidElementTests.js
+++ b/test/shared/isValidElementTests.jsx
@@ -1,4 +1,5 @@
-/** @jsx createElement */
+// @jsxRuntime classic
+// @jsx createElement
 
 export function isValidElementTests(
 	expect,
diff --git a/vitest.config.mjs b/vitest.config.mjs
index 91d23b422d..c61a399c94 100644
--- a/vitest.config.mjs
+++ b/vitest.config.mjs
@@ -1,6 +1,5 @@
 import { defineConfig } from 'vitest/config';
 import { transformAsync } from '@babel/core';
-import fs from 'node:fs/promises';
 import { readFileSync } from 'node:fs';
 import path from 'node:path';
 
@@ -137,11 +136,11 @@ export default defineConfig({
 	},
 	esbuild: {
 		loader: 'jsx',
-		include: /.*\.js$/,
+		include: /.*\.jsx$/,
 		exclude: ['node_nodules'],
 		jsx: 'transform',
-		jsxImportSource: 'preact',
-		jsxDev: true
+		jsxFactory: 'createElement',
+		jsxFragment: 'Fragment',
 	},
 	plugins: [
 		{
@@ -167,7 +166,7 @@ export default defineConfig({
 							}
 						]
 					],
-					include: ['**/src/**/*.js', '**/test/**/*.js']
+					include: ['**/src/**/*.js', '**/test/**/*.js', '**/test/**/*.jsx'],
 				});
 
 				return {
@@ -193,19 +192,6 @@ export default defineConfig({
 		],
 		esbuildOptions: {
 			alias,
-			plugins: [
-				{
-					name: 'load-js-files-as-jsx',
-					setup(build) {
-						build.onLoad({ filter: /.*\.js$/ }, async args => {
-							return {
-								loader: 'jsx',
-								contents: await fs.readFile(args.path, 'utf8')
-							};
-						});
-					}
-				}
-			]
 		}
 	},
 	test: {
@@ -241,15 +227,15 @@ export default defineConfig({
 			{
 				extends: true,
 				test: {
-					include: ['./test/{shared,node,ts}/**/*.test.js']
+					include: ['./test/{shared,node,ts}/**/*.test.js?(x)']
 				}
 			},
 			{
 				extends: true,
 				test: {
 					include: [
-						'{debug,devtools,hooks,compat,test-utils,jsx-runtime}/test/{browser,shared}/**/*.test.js',
-						'./test/{browser,shared}/**/*.test.js'
+						'{debug,devtools,hooks,compat,test-utils,jsx-runtime}/test/{browser,shared}/**/*.test.js?(x)',
+						'./test/{browser,shared}/**/*.test.js?(x)'
 					],
 					setupFiles: ['./vitest.setup.js'],
 					// dangerouslyIgnoreUnhandledErrors: true,