Improve reducer warning (#207)

* Fix formatting

* Improve missing reducer error message

Author: markerikson

docs/api/createAction.md

@@ -49,9 +49,9 @@ console.log(`The action type is: ${increment}`)
 
 ## Using Prepare Callbacks to Customize Action Contents
 
-By default, the generated action creators accept a single argument, which becomes `action.payload`.  This requires the caller to construct the entire payload correctly and pass it in.
+By default, the generated action creators accept a single argument, which becomes `action.payload`. This requires the caller to construct the entire payload correctly and pass it in.
 
-In many cases, you may want to write additional logic to customize the creation of the `payload`  value, such as accepting multiple parameters for the action creator, generating a random ID, or getting the current timestamp.  To do this, `createAction` accepts an optional second argument: a "prepare callback" that will be used to construct the payload value.  
+In many cases, you may want to write additional logic to customize the creation of the `payload` value, such as accepting multiple parameters for the action creator, generating a random ID, or getting the current timestamp. To do this, `createAction` accepts an optional second argument: a "prepare callback" that will be used to construct the payload value.
 
 ```js
 import v4 from 'uuid/v4'

src/configureStore.test.ts

@@ -50,7 +50,7 @@ describe('configureStore', () => {
   describe('given no reducer', () => {
     it('throws', () => {
       expect(configureStore).toThrow(
-        'Reducer argument must be a function or an object of functions that can be passed to combineReducers'
+        '"reducer" is a required argument, and must be a function or an object of functions that can be passed to combineReducers'
       )
     })
   })

src/configureStore.ts

@@ -109,7 +109,7 @@ export function configureStore<S = any, A extends Action = AnyAction>(
     rootReducer = combineReducers(reducer)
   } else {
     throw new Error(
-      'Reducer argument must be a function or an object of functions that can be passed to combineReducers'
+      '"reducer" is a required argument, and must be a function or an object of functions that can be passed to combineReducers'
     )
   }
 

type-tests/files/createSlice.typetest.ts

@@ -170,29 +170,27 @@ function expectType<T>(t: T) {
   })
 }
 
-
 /*
  * Test: if no Payload Type is specified, accept any payload
  * see https://github.com/reduxjs/redux-starter-kit/issues/165
  */
 {
   const initialState = {
     name: null
-  };
-
+  }
 
   const mySlice = createSlice({
     initialState,
     reducers: {
       setName: (state, action) => {
-        state.name = action.payload;
+        state.name = action.payload
       }
     }
-  });
+  })
 
-  const x = mySlice.actions.setName;
+  const x = mySlice.actions.setName
 
-  mySlice.actions.setName(null);
-  mySlice.actions.setName("asd");
-  mySlice.actions.setName(5);
-}
+  mySlice.actions.setName(null)
+  mySlice.actions.setName('asd')
+  mySlice.actions.setName(5)
+}