Add a test for 'Expected the nextReducer to be a function.' and fix ESLint

Author: zalmoxisus

src/instrument.js

@@ -337,7 +337,7 @@ export default function instrument(monitorReducer = () => null) {
   return createStore => (reducer, initialState, enhancer) => {
     function liftReducer(r) {
       if (typeof r !== 'function') {
-        throw new Error('Expected the nextReducer to be a function.')
+        throw new Error('Expected the nextReducer to be a function.');
       }
       return liftReducerWith(r, initialState, monitorReducer);
     }

test/instrument.spec.js

@@ -322,4 +322,10 @@ describe('instrument', () => {
       expect(importMonitoredLiftedStore.getState()).toEqual(exportedState);
     });
   });
+
+  it('throws if reducer is not a function', () => {
+    expect(() =>
+      instrument()(createStore)()
+    ).toThrow('Expected the nextReducer to be a function.');
+  });
 });