reduceActions

Testing helper. Calculates the state after dispatching an sequence of actions to a specific reducer, starting from the initial state.
// JavaScript
​
function reduceActions(reducer, ...actions)
// TypeScript
​
function reduceActions<S, A extends Action, AS extends A[]>(
  reducer: Reducer<S, A>,
  ...actions: AS
): S
Details
reduceActions calls reducer with each of the passed actions - as if these had been dispatched in the specified order - and returns the resulting state. For the first reducer call, the reducer's initial state (as determined by getInitialState) is used; each following call receives the state returned by the previous one.
If called without any actions, reduceActions simply returns the reducer's initial state - that is, reduceActions(reducer) is equivalent to getInitialState(reducer).
This helper is meant for use in reducer tests.
Examples
Basic usage:
import { reduceActions } from 'redux-preboiled'
​
const reducer = (state = 0, action) => {
  switch (action.type) {
    case 'increment':
      return state + 1
    case 'multiply':
      return state * action.payload
    default:
      return state
  }
}
​
reduceActions(reducer, { type: 'increment' })
// => 1
​
reduceActions(
  reducer,
  { type: 'increment' },
  { type: 'increment' },
  { type: 'multiply', payload: 2 }
)
// => 4
​
reduceActions(reducer)
// => 0
Usage in a Jest test:
import { reduceActions } from 'redux-preboiled'
import counterReducer, {
  increment,
  multiply
} from './counter.redux'
​
test('increment', () => {
  const state = reduceActions(counterReducer, increment())
  expect(state).toEqual(1)
})
​
test('increment and multiply', () => {
  const state = reduceActions(
    counterReducer,
    increment(),
    increment(),
    multiply(4)
  )
  expect(state).toEqual(8)
})
See Also
​Testing guide
API - Previous
onAction
Next - API
withInitialState
Last updated 2 years ago