Clarify changeAuthState docs

Author: dmurvihill

API.md

@@ -178,13 +178,14 @@ Before changing the authentication state, `changeAuthState` checks the
 `onAuthStateChanged` listeners will only be triggered if the data is not
 deeply equal.
 
-To simulate no user being authenticated, pass `null` for `user`.
-This operation is queued until the next `flush`.
+`user` should be a `MockUser` object or an object with the same fields
+as `MockUser`. To simulate no user being authenticated, pass `null` for
+`user`. This operation is queued until the next `flush`.
 
 Example:
 
 ```js
-ref.changeAuthState(new User(ref, {
+ref.changeAuthState(new MockUser(ref, {
   uid: 'theUid',
   email: '[email protected]',
   emailVerified: true,

test/unit/docs.js

@@ -1,16 +1,16 @@
-const User = require('../../src/user');
+const MockUser = require('../../src/user');
 
 describe('API.md', () => {
-  describe('Auth example for', () => {
+  describe('Auth example for changeAuthState', () => {
 
     let ref;
     beforeEach(() => {
       const Authentication = require('../../').MockAuthentication;
       ref = new Authentication();
     });
 
-    it('changeAuthState works as described', () => {
-      ref.changeAuthState(new User(ref, {
+    it('works as described', () => {
+      ref.changeAuthState(new MockUser(ref, {
         uid: 'theUid',
         email: '[email protected]',
         emailVerified: true,