How to test selectors in saga that take action values as props?

[billjohnston]

Having issues testing a selector that takes other arguments besides state

export function* exampleSaga(action) {
    const selectVar = yield select(state => exampleSelector(state, { id: action.id }))
    ...
}

describe('exampleSaga', () => {
    let it = sagaHelper(exampleSaga(mockAction))
    it('should yield x', (result) => {
        expect(result).toEqual(
            select(state => exampleSelector(state, { id: mockAction.id }))
        )
        return 'x'
    })
})

I've also tried saving the selector as a separate variable:

export const exampleSelectorFn = (action) => (state) => (
    shouldChangeRouteSelector(state, { action: action.id })
)
export function* exampleSaga(action) {
    const selectVar = yield select(exampleSelectorFn(action))
    ...
}

describe('exampleSaga', () => {
    let it = sagaHelper(exampleSaga(mockAction))
    it('should yield x', (result) => {
        expect(result).toEqual(
            select(exampleSelectorFn(mockAction))
        )
        return 'x'
    })
})

Both returns this (using jest):

Expected value to equal:
    {"@@redux-saga/IO": true, "SELECT": {"args": Array [], "selector": [Function anonymous]}}
Received:
    {"@@redux-saga/IO": true, "SELECT": {"args": Array [], "selector": [Function anonymous]}}

Difference:

Compared values have no visual difference.

[antoinejaussoin]

You shouldn't call selectors directly within select: instead of

const selectVar = yield select(state => exampleSelector(state, { id: action.id }))

use

const selectVar = yield select(exampleSelector, { id: action.id })

This will have the same result (the second parameter will be passed by redux-saga to your selector), but you can test test easily that the select function was called using the exampleSelector function and the other parameter.

[billjohnston]

This works, thank you