Update helpers for warning messages (#3638)

This doesn't change any behavior. It just syncs up the logic to the
latest that I have elsewhere.

Author: taion

modules/__tests__/shouldWarn.js

@@ -1,5 +1,3 @@
-/*eslint no-console: 0*/
-
 export default function shouldWarn(about) {
-  console.error.expected.push(about)
+  console.error.expected.push(about) // eslint-disable-line no-console
 }

tests.webpack.js

@@ -1,18 +1,23 @@
 /* eslint-env mocha */
-/* eslint-disable no-console */
 
 import expect from 'expect'
 
 import { _resetWarned } from './modules/routerWarning'
 
 beforeEach(() => {
+  /* eslint-disable no-console */
   expect.spyOn(console, 'error').andCall(msg => {
-    for (const about of console.error.expected) {
+    let expected = false
+
+    console.error.expected.forEach(about => {
       if (msg.indexOf(about) !== -1) {
         console.error.warned[about] = true
-        return
+        expected = true
       }
-    }
+    })
+
+    if (expected)
+      return
 
     console.error.threw = true
     throw new Error(msg)
@@ -21,18 +26,21 @@ beforeEach(() => {
   console.error.expected = []
   console.error.warned = Object.create(null)
   console.error.threw = false
+  /* eslint-enable no-console */
 })
 
 afterEach(() => {
-  if (!console.error.threw) {
-    console.error.expected.forEach(about => {
-      expect(console.error.warned[about]).toExist(
-        `Missing expected warning: ${about}`
-      )
+  /* eslint-disable no-console */
+  const { threw, expected, warned } = console.error
+  console.error.restore()
+
+  if (!threw) {
+    expected.forEach(about => {
+      expect(warned[about]).toExist(`Missing expected warning: ${about}`)
     })
   }
+  /* eslint-enable no-console */
 
-  console.error.restore()
   _resetWarned()
 })