use createReducer for createSlice and add tests

Author: neurosnap

src/createSlice.js

@@ -1,6 +1,5 @@
-import createNextState from 'immer';
+import { createReducer } from './createReducer';
 
-const defaultReducer = (state) => state;
 const getType = (slice, action) =>
   slice ? `${slice}/${action}` : action;
 
@@ -19,11 +18,7 @@ export default function createSlice({
     {},
   );
 
-  const reducer = (state = initialState, { type, payload }) => {
-    const actionReducer = reducerMap[type] || defaultReducer;
-    const produce = (draft) => actionReducer(draft, payload);
-    return createNextState(state, produce);
-  };
+  const reducer = createReducer(initialState, reducerMap);
 
   const actionMap = actionKeys.reduce(
     (map, action) => {

src/createSlice.test.js

@@ -0,0 +1,70 @@
+import createSlice from './createSlice'
+
+describe('createSlice', () => {
+  describe('when slice is empty', () => {
+    const { actions, reducer } = createSlice({
+      actions: {
+        increment: state => state + 1,
+        multiply: (state, action) => state * action.payload
+      },
+      initialState: 0
+    })
+
+    it('should create increment action', () => {
+      expect(actions.hasOwnProperty('increment')).toBe(true)
+    })
+
+    it('should create multiply action', () => {
+      expect(actions.hasOwnProperty('multiply')).toBe(true)
+    })
+
+    it('should have the correct action for increment', () => {
+      expect(actions.increment()).toEqual({
+        type: 'increment',
+        payload: undefined
+      })
+    })
+
+    it('should have the correct action for multiply', () => {
+      expect(actions.multiply(3)).toEqual({
+        type: 'multiply',
+        payload: 3
+      })
+    })
+
+    describe('when using reducer', () => {
+      it('should return the correct value from reducer with increment', () => {
+        expect(reducer(undefined, actions.increment())).toEqual(1)
+      })
+
+      it('should return the correct value from reducer with multiply', () => {
+        expect(reducer(2, actions.multiply(3))).toEqual(6)
+      })
+    })
+  })
+
+  describe('when passing slice', () => {
+    const { actions, reducer } = createSlice({
+      actions: {
+        increment: state => state + 1
+      },
+      initialState: 0,
+      slice: 'cool'
+    })
+
+    it('should create increment action', () => {
+      expect(actions.hasOwnProperty('increment')).toBe(true)
+    })
+
+    it('should have the correct action for increment', () => {
+      expect(actions.increment()).toEqual({
+        type: 'cool/increment',
+        payload: undefined
+      })
+    })
+
+    it('should return the correct value from reducer', () => {
+      expect(reducer(undefined, actions.increment())).toEqual(1)
+    })
+  })
+})