Add docs how to use firebase messaging mock

Author: raman-nbg

README.md

@@ -35,6 +35,7 @@ Firebase Mock supports the client-side [JavaScript API](https://firebase.google.
 * Authentication
   * [Basic](tutorials/admin/authentication.md)
   * [JWT Tokens](tutorials/admin/tokens.md)
+* [Messaging](tutorials/admin/messaging.md)
 * [Realtime Database](tutorials/admin/rtdb.md)
 * [Firestore](tutorials/admin/firestore.md)
 * [Storage](tutorials/admin/storage.md)

tutorials/admin/messaging.md

@@ -0,0 +1,92 @@
+# Tutorial: Authentication
+
+MockFirebase replaces most of Firebase's messaging method of the admin API with simple mocks. Messaging methods will always succeed unless an error is specifically specified using [`failNext`](../API.md#failnextmethod-err---undefined).
+
+## Send message
+
+In this example, we'll create send a new message using Firebase messaging.
+
+##### Source
+
+```js
+var ref;
+var messageService = {
+  messaging: function () {
+    if (!ref) ref = firebase.messaging();
+    return ref;
+  },
+  send: function () {
+    var message = {
+
+    };
+    messageService.ref().send();
+  },
+}
+```
+
+##### Test
+
+```js
+MockFirebase.override();
+var result = messageService.send();
+messageService.messaging().flush();
+result.then(function (messageId) {
+  console.log(messageId);
+});
+```
+
+## Supported methods
+
+- [send(message: Message, dryRun?: boolean): Promise<string>](https://firebase.google.com/docs/reference/admin/node/admin.messaging.Messaging.html#send)
+- [sendAll(messages: Array<Message>, dryRun?: boolean): Promise<BatchResponse>](https://firebase.google.com/docs/reference/admin/node/admin.messaging.Messaging.html#send-all)
+- [sendMulticast(message: MulticastMessage, dryRun?: boolean): Promise<BatchResponse>](https://firebase.google.com/docs/reference/admin/node/admin.messaging.Messaging.html#send-multicast)
+
+## Set custom message response
+In some cases it could be necessary to fake a custom send response (like a [BatchResponse](https://firebase.google.com/docs/reference/admin/node/admin.messaging.BatchResponse.html)). In this cases you can use `firebase.messaging().nextResult(methodName, result)` (similar to `firebase.messaging().failNext(methodName, err)`).
+
+##### Source
+
+```js
+var ref;
+var messageService = {
+  messaging: function () {
+    if (!ref) ref = firebase.messaging();
+    return ref;
+  },
+  send: function () {
+    var message = {
+
+    };
+    messageService.ref().send();
+  },
+}
+```
+
+##### Test
+
+```js
+MockFirebase.override();
+var batchResponse = {
+  failureCount: 1,
+  response: [
+    {
+      error: {...},
+      messageId: undefined,
+      success: false
+    },
+    {
+      error: undefined,
+      messageId: '...',
+      success: true
+    }
+  ],
+  successCount: 1
+}
+messageService.messaging().nextResult('sendAll', batchResponse);
+var result = messageService.sendAll();
+messageService.messaging().flush();
+result.then(function (res) {
+  console.assert(res.failureCount === 1, '1 message failed');
+  console.assert(res.successCount === 1, '1 message succeeded');
+});
+```