Dfyjkt

I getting following error when I tried to change the value in control.

Uncaught (in promise) Error: A state mutation was detected between
dispatches, in the path test. This may cause incorrect behavior.

Below is the code

Reducer

export default function testReducer(state = , action) 
 switch (action.type) 
 case types.UPDATE_TEST_SUCCESS:
 return 
 ...state,
 test: action.test
 ;
 default:
 return state;
 

Action

export function saveTest(testData) 
 return function(dispatch) 
 return testApi.testExam(testData).then(savedData => 
 dispatch(updateTestSuccess(savedData));
 );
 ;


export function updateTestSuccess(exam) 
 return type: types.UPDATE_Test_SUCCESS, exam ;

API

static saveTest(testData) 
 let url = services.GET_Test_URL;
 return fetch(url, 
 method: 'PUT',
 body: JSON.stringify(testData).toString(), 
 dataType : "json",
 headers: 
 'Accept': 'application/json',
 'Content-Type': 'application/json'
 
 ).then((response) => response.json())
 .then((testD) => Object.assign(, testD))
 .catch((error) => throw (error); );