javascript - Testing the redux store using Jest -

i've set following function configure redux store

const configurestore = (initialstate) => {   console.log(initialstate);   const store = createstore(     rootreducer,     initialstate,     applymiddleware(       thunkmiddleware     )   );    console.log(store.getstate());   return store; }; 

now, running normal app entry point, console logs show, example:

-> initial state = { test: "test" } -> (store gets created) -> store state = { test: "test" } 

thats good, , expected. i'm trying confirm behaviour following jest test

it("should set supplied initial state", () => {     const initialstate = {       teststate: "test"     };      const store = configurestore(initialstate);     expect(store.getstate()).toequal({       teststate: "test"     });   }); 

this test failing, store.getstate() returning undefined. can see console logs configurestore function, , showing:

-> initial state = { test: "test" } -> (store gets created) -> store state = undefined 

why behaviour different? jest mocking createstore function? i've read jest no longer auto-mocks dependencies, why case? i'm new jest unit testing, light can shed on issue appreciated.

edit: realise i'm testing redux function, unnecessary. regardless, i'd understand testing behaviour that's causing issue.

second edit: writing own createstore function follows makes test pass:

const createstore = (reducer, initstate, middleware) => {   return {     getstate: () => (initstate)   }; }; 

but still doesn't answer why redux createstore function behaving differently in test environment.

all actions go through your:

rootreducer 

including action fired when redux instantiates e.g. initial action has type '@@redux/init'.

so if ever unexpected state check reducer behaving expected.

as found, reducer not behaving expected mock instance not being preserved across tests.