docs: testing for using typescript (#1303)

docs/guides/testing.mdx

@@ -38,6 +38,36 @@ The way you mock a dependency depends on your test runner/library.
 
 In [jest](https://jestjs.io/), you can create a `__mocks__/zustand.js` and place the code in that file. If your app is using `zustand/vanilla` instead of `zustand`, then you'll have to place the above code in `__mocks__/zustand/vanilla.js`.
 
+### TypeScript usage
+
+If you are using zustand, as documented in [TypeScript Guide](./typescript.md), use the following code:
+
+```tsx
+import actualCreate, { StateCreator } from 'zustand'
+// const actualCreate = jest.requireActual('zustand') // if using jest
+import { act } from 'react-dom/test-utils'
+
+// a variable to hold reset functions for all stores declared in the app
+const storeResetFns = new Set<() => void>()
+
+// when creating a store, we get its initial state, create a reset function and add it in the set
+const create =
+  () =>
+  <S,>(createState: StateCreator<S>) => {
+    const store = actualCreate<S>(createState)
+    const initialState = store.getState()
+    storeResetFns.add(() => store.setState(initialState, true))
+    return store
+  }
+
+// Reset all stores after each test run
+beforeEach(() => {
+  act(() => storeResetFns.forEach((resetFn) => resetFn()))
+})
+
+export default create
+```
+
 ## Resetting state between tests in **react-native** and **jest**
 
 You should use the following code in the `__mocks__/zustand.js` file (the `__mocks__` directory should be adjacent to node_modules, placed in the same folder as node_modules, unless you configured roots to point to a folder other than the project root [jest docs: mocking node modules](https://jestjs.io/docs/manual-mocks#mocking-node-modules)):