diff --git a/packages/core/src/getChildEventSubscriber.js b/packages/core/src/getChildEventSubscriber.js
index 8839248a..99c232e0 100644
--- a/packages/core/src/getChildEventSubscriber.js
+++ b/packages/core/src/getChildEventSubscriber.js
@@ -69,8 +69,8 @@ export default function getChildEventSubscriber(addListener, key) {
       const lastRoutes = lastState && lastState.routes;
       const routes = state && state.routes;
 
-      const lastFocusKey =
-        lastState && lastState.routes && lastState.routes[lastState.index].key;
+      // const lastFocusKey =
+      //   lastState && lastState.routes && lastState.routes[lastState.index].key;
       const focusKey = routes && routes[state.index].key;
 
       const isChildFocused = focusKey === key;
diff --git a/packages/core/src/getChildNavigation.js b/packages/core/src/getChildNavigation.js
index 441c05cb..ecc89723 100644
--- a/packages/core/src/getChildNavigation.js
+++ b/packages/core/src/getChildNavigation.js
@@ -1,7 +1,6 @@
 import getChildEventSubscriber from './getChildEventSubscriber';
 import getChildRouter from './getChildRouter';
 import getNavigationActionCreators from './routers/getNavigationActionCreators';
-import invariant from './utils/invariant';
 
 const createParamGetter = route => (paramName, defaultValue) => {
   const params = route.params;
diff --git a/packages/core/src/index.js b/packages/core/src/index.js
index 365b66f3..653d802c 100644
--- a/packages/core/src/index.js
+++ b/packages/core/src/index.js
@@ -1,4 +1,4 @@
-/* eslint global-require: 0 */
+/* eslint-disable import/no-commonjs */
 
 module.exports = {
   get StateUtils() {
diff --git a/packages/core/src/routers/StackRouter.js b/packages/core/src/routers/StackRouter.js
index beb8595c..ca782e71 100644
--- a/packages/core/src/routers/StackRouter.js
+++ b/packages/core/src/routers/StackRouter.js
@@ -15,7 +15,7 @@ function behavesLikePushAction(action) {
   );
 }
 
-const defaultActionCreators = (route, navStateKey) => ({});
+const defaultActionCreators = () => ({});
 
 function isResetToRootStack(action) {
   return action.type === StackActions.RESET && action.key === null;
diff --git a/packages/core/src/routers/SwitchRouter.js b/packages/core/src/routers/SwitchRouter.js
index 1b028ebe..1753636d 100644
--- a/packages/core/src/routers/SwitchRouter.js
+++ b/packages/core/src/routers/SwitchRouter.js
@@ -7,7 +7,7 @@ import StackActions from './StackActions';
 import validateRouteConfigMap from './validateRouteConfigMap';
 import { createPathParser } from './pathUtils';
 
-const defaultActionCreators = (route, navStateKey) => ({});
+const defaultActionCreators = () => ({});
 
 function childrenUpdateWithoutSwitchingIndex(actionType) {
   return [
@@ -36,7 +36,6 @@ export default (routeConfigs, config = {}) => {
   const initialRouteIndex = order.indexOf(initialRouteName);
   const childRouters = {};
   order.forEach(routeName => {
-    const routeConfig = routeConfigs[routeName];
     childRouters[routeName] = null;
     const screen = getScreenForRouteName(routeConfigs, routeName);
     if (screen.router) {
diff --git a/packages/core/src/routers/__tests__/PathHandling-test.js b/packages/core/src/routers/__tests__/PathHandling-test.js
index 0863565c..380fa76e 100644
--- a/packages/core/src/routers/__tests__/PathHandling-test.js
+++ b/packages/core/src/routers/__tests__/PathHandling-test.js
@@ -5,7 +5,6 @@ import React from 'react';
 import SwitchRouter from '../SwitchRouter';
 import StackRouter from '../StackRouter';
 import TabRouter from '../TabRouter';
-import StackActions from '../StackActions';
 import NavigationActions from '../../NavigationActions';
 import { _TESTING_ONLY_normalize_keys } from '../KeyGenerator';
 
diff --git a/packages/core/src/routers/__tests__/Routers-test.js b/packages/core/src/routers/__tests__/Routers-test.js
index a8e00e42..bbb1f643 100644
--- a/packages/core/src/routers/__tests__/Routers-test.js
+++ b/packages/core/src/routers/__tests__/Routers-test.js
@@ -19,7 +19,7 @@ const ROUTERS = {
   SwitchRouter,
 };
 
-const dummyEventSubscriber = (name, handler) => ({
+const dummyEventSubscriber = () => ({
   remove: () => {},
 });
 
diff --git a/packages/core/src/routers/__tests__/StackRouter-test.js b/packages/core/src/routers/__tests__/StackRouter-test.js
index e86d6147..7a8dfd95 100644
--- a/packages/core/src/routers/__tests__/StackRouter-test.js
+++ b/packages/core/src/routers/__tests__/StackRouter-test.js
@@ -397,7 +397,6 @@ describe('StackRouter', () => {
       },
       state
     );
-    const barKey = state2.routes[1].routes[0].key;
     const state3 = router.getStateForAction(
       {
         type: StackActions.PUSH,
@@ -429,7 +428,6 @@ describe('StackRouter', () => {
       },
       state
     );
-    const barKey = state2.routes[1].routes[0].key;
     const state3 = router.getStateForAction(
       {
         type: StackActions.POP,
@@ -440,9 +438,6 @@ describe('StackRouter', () => {
   });
 
   test('Handle navigation to nested navigator', () => {
-    const state = TestStackRouter.getStateForAction({
-      type: NavigationActions.INIT,
-    });
     const action = TestStackRouter.getActionForPathAndParams('fo/22/b/hello');
     /* $FlowFixMe */
     const state2 = TestStackRouter.getStateForAction(action);
@@ -734,19 +729,17 @@ describe('StackRouter', () => {
       bar: { screen: () => <div /> },
     });
     const initState = TestRouter.getStateForAction(NavigationActions.init());
-    for (key of ['a', null]) {
-      const pushedState = TestRouter.getStateForAction(
-        NavigationActions.navigate({ routeName: 'bar', key: 'a' }),
-        initState
-      );
-      expect(pushedState.index).toEqual(1);
-      expect(pushedState.routes[1].routeName).toEqual('bar');
-      const pushedTwiceState = TestRouter.getStateForAction(
-        NavigationActions.navigate({ routeName: 'bar', key: 'a' }),
-        pushedState
-      );
-      expect(pushedTwiceState).toEqual(null);
-    }
+    const pushedState = TestRouter.getStateForAction(
+      NavigationActions.navigate({ routeName: 'bar', key: 'a' }),
+      initState
+    );
+    expect(pushedState.index).toEqual(1);
+    expect(pushedState.routes[1].routeName).toEqual('bar');
+    const pushedTwiceState = TestRouter.getStateForAction(
+      NavigationActions.navigate({ routeName: 'bar', key: 'a' }),
+      pushedState
+    );
+    expect(pushedTwiceState).toEqual(null);
   });
 
   // https://github.com/react-navigation/react-navigation/issues/4063
@@ -1905,7 +1898,7 @@ describe('StackRouter', () => {
     expect(activeState5.routes[activeState5.index].routeName).toEqual('Bar');
   });
 
-  test('order of handling navigate action is correct for nested stackrouters', () => {
+  test('order of handling navigate action is correct for nested stackrouters 2', () => {
     const Screen = () => <div />;
     const NestedStack = () => <div />;
     const OtherNestedStack = () => <div />;
diff --git a/packages/core/src/routers/__tests__/TabRouter-test.js b/packages/core/src/routers/__tests__/TabRouter-test.js
index e4a67cab..28438975 100644
--- a/packages/core/src/routers/__tests__/TabRouter-test.js
+++ b/packages/core/src/routers/__tests__/TabRouter-test.js
@@ -527,7 +527,7 @@ describe('TabRouter', () => {
     });
   });
 
-  test.only('Handles path configuration', () => {
+  test('Handles path configuration', () => {
     const ScreenA = () => <div />;
     const ScreenB = () => <div />;
     const router = TabRouter({
diff --git a/packages/core/src/routers/__tests__/createConfigGetter-test.js b/packages/core/src/routers/__tests__/createConfigGetter-test.js
index 0a79d886..033d80b7 100644
--- a/packages/core/src/routers/__tests__/createConfigGetter-test.js
+++ b/packages/core/src/routers/__tests__/createConfigGetter-test.js
@@ -1,13 +1,11 @@
 import { Component } from 'react';
 import createConfigGetter from '../createConfigGetter';
 
-const dummyEventSubscriber = (name: string, handler: (*) => void) => ({
+const dummyEventSubscriber = () => ({
   remove: () => {},
 });
 
 test('should get config for screen', () => {
-  /* eslint-disable react/no-multi-comp */
-
   class HomeScreen extends Component {
     static navigationOptions = ({ navigation }) => ({
       title: `Welcome ${
@@ -147,8 +145,6 @@ test('should get config for screen', () => {
 });
 
 test('should throw if the route does not exist', () => {
-  /* eslint-disable react/no-multi-comp */
-
   const HomeScreen = () => null;
   HomeScreen.navigationOptions = {
     title: 'Home screen',
diff --git a/packages/core/src/routers/pathUtils.js b/packages/core/src/routers/pathUtils.js
index be9eea1b..588209bd 100644
--- a/packages/core/src/routers/pathUtils.js
+++ b/packages/core/src/routers/pathUtils.js
@@ -1,17 +1,11 @@
+/* eslint-disable import/no-commonjs */
+
 import pathToRegexp, { compile } from 'path-to-regexp';
 import NavigationActions from '../NavigationActions';
 import invariant from '../utils/invariant';
 
 const queryString = require('query-string');
 
-function isEmpty(obj) {
-  if (!obj) return true;
-  for (let key in obj) {
-    return false;
-  }
-  return true;
-}
-
 export const getParamsFromPath = (inputParams, pathMatch, pathMatchKeys) => {
   const params = pathMatch.slice(1).reduce(
     // iterate over matched path params
@@ -123,9 +117,6 @@ export const createPathParser = (
   const getActionForPathAndParams = (pathToResolve = '', inputParams = {}) => {
     // Attempt to match `pathToResolve` with a route in this router's routeConfigs, deferring to child routers
 
-    let matchedAction = null;
-
-    // eslint-disable-next-line no-restricted-syntax
     for (const [routeName, path] of paths) {
       const { exactRe, exactReKeys, extendedPathRe, extendedPathReKeys } = path;
       const childRouter = childRouters[routeName];
@@ -152,7 +143,6 @@ export const createPathParser = (
       }
     }
 
-    // eslint-disable-next-line no-restricted-syntax
     for (const [routeName, path] of paths) {
       const { extendedPathRe, extendedPathReKeys } = path;
       const childRouter = childRouters[routeName];
diff --git a/packages/core/src/utils/invariant.js b/packages/core/src/utils/invariant.js
index ef63437c..99121cf0 100644
--- a/packages/core/src/utils/invariant.js
+++ b/packages/core/src/utils/invariant.js
@@ -1,3 +1,5 @@
+/* eslint-disable import/no-commonjs */
+
 /**
  * Use invariant() to assert state which your program assumes to be true.
  *
@@ -9,7 +11,7 @@
  * will remain to ensure logic does not differ in production.
  */
 
-var validateFormat = function(format) {};
+var validateFormat = function() {};
 
 if (__DEV__) {
   validateFormat = function(format) {
diff --git a/packages/core/src/views/__tests__/NavigationEvents-test.js b/packages/core/src/views/__tests__/NavigationEvents-test.js
index ed29cef1..7b5bc0fb 100644
--- a/packages/core/src/views/__tests__/NavigationEvents-test.js
+++ b/packages/core/src/views/__tests__/NavigationEvents-test.js
@@ -3,7 +3,7 @@ import renderer from 'react-test-renderer';
 import NavigationEvents from '../NavigationEvents';
 import { NavigationProvider } from '../NavigationContext';
 
-const createListener = () => payload => {};
+const createListener = () => () => {};
 
 // An easy way to create the 4 listeners prop
 const createEventListenersProp = () => ({
@@ -101,6 +101,7 @@ describe('NavigationEvents', () => {
     checkAddListenerCalledWith('willFocus', eventListenerProps.onWillFocus);
     checkAddListenerCalledWith('didBlur', eventListenerProps.onDidBlur);
     checkAddListenerCalledWith('didFocus', eventListenerProps.onDidFocus);
+    component.unmount();
   });
 
   it('add all listeners with navigation context', () => {
@@ -122,6 +123,7 @@ describe('NavigationEvents', () => {
     checkAddListenerCalledWith('willFocus', eventListenerProps.onWillFocus);
     checkAddListenerCalledWith('didBlur', eventListenerProps.onDidBlur);
     checkAddListenerCalledWith('didFocus', eventListenerProps.onDidFocus);
+    component.unmount();
   });
 
   it('remove all listeners on unmount', () => {
@@ -159,6 +161,7 @@ describe('NavigationEvents', () => {
     );
     checkAddListenerCalled(1);
     checkAddListenerCalledWith('didFocus', listener);
+    component.unmount();
   });
 
   it('do not attempt to add/remove stable listeners on update', () => {