grafana/contribute/style-guides/redux.md

# Redux framework

Grafana uses [Redux Toolkit](https://redux-toolkit.js.org/) to handle Redux boilerplate code.
> Some of our Reducers are used by Angular and therefore state is to be considered as mutable for those reducers.

## Test functionality

### reducerTester

Fluent API that simplifies the testing of reducers

#### Usage

```typescript
reducerTester()
  .givenReducer(someReducer, initialState)
  .whenActionIsDispatched(someAction('reducer tests'))
  .thenStateShouldEqual({ ...initialState, data: 'reducer tests' });
```

#### Complex usage
Sometimes you encounter a `resulting state` that contains properties that are hard to compare, such as `Dates`, but you still want to compare that other props in state are correct.

Then you can use `thenStatePredicateShouldEqual` function on `reducerTester` that will return the `resulting state` so that you can expect upon individual properties..

```typescript
reducerTester()
  .givenReducer(someReducer, initialState)
  .whenActionIsDispatched(someAction('reducer tests'))
  .thenStatePredicateShouldEqual(resultingState => {
    expect(resultingState.data).toEqual('reducer tests');
    return true;  
  });
```

### thunkTester

Fluent API that simplifies the testing of thunks.

#### Usage

```typescript
const dispatchedActions = await thunkTester(initialState)
    .givenThunk(someThunk)
    .whenThunkIsDispatched(arg1, arg2, arg3);

expect(dispatchedActions).toEqual([someAction('reducer tests')]);
```

## Typing of connected props

It is possible to infer connected props automatically from `mapStateToProps` and `mapDispatchToProps` using a helper type `ConnectedProps` from Redux. For this to work the `connect` call has to be split into two parts.

```typescript
import { connect, ConnectedProps } from 'react-redux'

const mapStateToProps = (state: StoreState) => {
  return {
    location: state.location,
    initDone: state.panelEditor.initDone,
    uiState: state.panelEditor.ui,
  };
};

const mapDispatchToProps = {
  updateLocation,
  initPanelEditor,
  panelEditorCleanUp,
  setDiscardChanges,
  updatePanelEditorUIState,
  updateTimeZoneForSession,
};

const connector = connect(mapStateToProps, mapDispatchToProps);

type Props = OwnProps & ConnectedProps<typeof connector>;

class PanelEditorUnconnected extends PureComponent<Props> {};

export const PanelEditor = connector(PanelEditorUnconnected);
```
For more examples, refer to the [Redux docs](https://react-redux.js.org/using-react-redux/static-typing#inferring-the-connected-props-automatically).