feat: Add worklet mock helper function for jest unit tests (#8882)

## Summary

This PR adds a helper `worklet` function to create worklet function
mocks (functions that pretend to be worklets instead of plain
functions). Sometimes behavior of our code is dependent on whether a
function is a worklet or not - to distinguish this behavior in tests, I
need to have a way to create function mocks that will be treated as
worklets.

Author: MatiPl01

packages/react-native-reanimated/src/jestUtils/common.ts

@@ -0,0 +1,24 @@
+'use strict';
+
+import type { WorkletFunction } from 'react-native-worklets';
+
+/**
+ * Converts any callback function to a mock worklet function for testing
+ * purposes. This function simulates a worklet by adding the required internal
+ * properties.
+ *
+ * @param callback - Optional callback function to wrap as a worklet. If not
+ *   provided, returns an empty worklet.
+ * @returns A mock worklet function with the required worklet properties.
+ */
+export const worklet = <Args extends unknown[] = [], ReturnValue = void>(
+  callback?: (...args: Args) => ReturnValue
+): WorkletFunction<Args, ReturnValue> => {
+  const fn = (callback ?? (() => undefined)) as WorkletFunction<
+    Args,
+    ReturnValue
+  >;
+  fn.__workletHash = Math.random();
+  fn.__closure = {};
+  return fn;
+};

…react-native-reanimated/src/jestUtils.ts …native-reanimated/src/jestUtils/index.tspackages/react-native-reanimated/src/jestUtils.ts renamed to packages/react-native-reanimated/src/jestUtils/index.ts packages/react-native-reanimated/src/jestUtils.ts renamed to packages/react-native-reanimated/src/jestUtils/index.ts

@@ -1,16 +1,17 @@
 /* eslint-disable @typescript-eslint/no-namespace */
 'use strict';
 
+import type React from 'react';
 import type { ReactTestInstance } from 'react-test-renderer';
 
-import { IS_JEST, logger, ReanimatedError } from './common';
+import { IS_JEST, logger, ReanimatedError } from '../common';
 import type {
   AnimatedComponentProps,
   AnimatedProps,
   IAnimatedComponentInternal,
   InitialComponentProps,
-} from './createAnimatedComponent/commonTypes';
-import type { DefaultStyle } from './hook/commonTypes';
+} from '../createAnimatedComponent/commonTypes';
+import type { DefaultStyle } from '../hook/commonTypes';
 
 declare global {
   namespace jest {
@@ -353,3 +354,6 @@ export const getAnimatedStyle = (component: ReactTestInstance) => {
     component as unknown as TestComponent
   );
 };
+
+/** @knipIgnore */
+export { worklet } from './common';

…t-native-reanimated/src/jestUtils.web.ts …ve-reanimated/src/jestUtils/index.web.tspackages/react-native-reanimated/src/jestUtils.web.ts renamed to packages/react-native-reanimated/src/jestUtils/index.web.ts packages/react-native-reanimated/src/jestUtils.web.ts renamed to packages/react-native-reanimated/src/jestUtils/index.web.ts

@@ -22,3 +22,5 @@ export function setUpTests() {
 export function getAnimatedStyle() {
   // NOOP
 }
+
+export { worklet } from './common';