diff --git a/.eslintignore b/.eslintignore
index 417342d..66758cc 100644
--- a/.eslintignore
+++ b/.eslintignore
@@ -1,2 +1,3 @@
 bin
+lib
 *.md
diff --git a/doc/api.md b/doc/api.md
index adb8c25..031db25 100644
--- a/doc/api.md
+++ b/doc/api.md
@@ -30,13 +30,13 @@ TelegramBot
         * [.sendMessage(chatId, text, [options])](#TelegramBot+sendMessage) ⇒ <code>Promise</code>
         * [.answerInlineQuery(inlineQueryId, results, [options])](#TelegramBot+answerInlineQuery) ⇒ <code>Promise</code>
         * [.forwardMessage(chatId, fromChatId, messageId, [options])](#TelegramBot+forwardMessage) ⇒ <code>Promise</code>
-        * [.sendPhoto(chatId, photo, [options])](#TelegramBot+sendPhoto) ⇒ <code>Promise</code>
-        * [.sendAudio(chatId, audio, [options])](#TelegramBot+sendAudio) ⇒ <code>Promise</code>
+        * [.sendPhoto(chatId, photo, [options], [fileOpts])](#TelegramBot+sendPhoto) ⇒ <code>Promise</code>
+        * [.sendAudio(chatId, audio, [options], [fileOpts])](#TelegramBot+sendAudio) ⇒ <code>Promise</code>
         * [.sendDocument(chatId, doc, [options], [fileOpts])](#TelegramBot+sendDocument) ⇒ <code>Promise</code>
         * [.sendSticker(chatId, sticker, [options])](#TelegramBot+sendSticker) ⇒ <code>Promise</code>
-        * [.sendVideo(chatId, video, [options])](#TelegramBot+sendVideo) ⇒ <code>Promise</code>
-        * [.sendVideoNote(chatId, videoNote, [options])](#TelegramBot+sendVideoNote) ⇒ <code>Promise</code>
-        * [.sendVoice(chatId, voice, [options])](#TelegramBot+sendVoice) ⇒ <code>Promise</code>
+        * [.sendVideo(chatId, video, [options], [fileOpts])](#TelegramBot+sendVideo) ⇒ <code>Promise</code>
+        * [.sendVideoNote(chatId, videoNote, [options], [fileOpts])](#TelegramBot+sendVideoNote) ⇒ <code>Promise</code>
+        * [.sendVoice(chatId, voice, [options], [fileOpts])](#TelegramBot+sendVoice) ⇒ <code>Promise</code>
         * [.sendChatAction(chatId, action, [options])](#TelegramBot+sendChatAction) ⇒ <code>Promise</code>
         * [.kickChatMember(chatId, userId, [options])](#TelegramBot+kickChatMember) ⇒ <code>Promise</code>
         * [.unbanChatMember(chatId, userId, [options])](#TelegramBot+unbanChatMember) ⇒ <code>Promise</code>
@@ -339,31 +339,41 @@ Forward messages of any kind.
 
 <a name="TelegramBot+sendPhoto"></a>
 
-### telegramBot.sendPhoto(chatId, photo, [options]) ⇒ <code>Promise</code>
+### telegramBot.sendPhoto(chatId, photo, [options], [fileOpts]) ⇒ <code>Promise</code>
 Send photo
 
 **Kind**: instance method of <code>[TelegramBot](#TelegramBot)</code>  
-**See**: https://core.telegram.org/bots/api#sendphoto  
+**See**
+
+- https://core.telegram.org/bots/api#sendphoto
+- https://github.com/yagop/node-telegram-bot-api/blob/master/doc/usage.md#sending-files
+
 
 | Param | Type | Description |
 | --- | --- | --- |
 | chatId | <code>Number</code> &#124; <code>String</code> | Unique identifier for the message recipient |
 | photo | <code>String</code> &#124; <code>stream.Stream</code> &#124; <code>Buffer</code> | A file path or a Stream. Can also be a `file_id` previously uploaded |
 | [options] | <code>Object</code> | Additional Telegram query options |
+| [fileOpts] | <code>Object</code> | Optional file related meta-data |
 
 <a name="TelegramBot+sendAudio"></a>
 
-### telegramBot.sendAudio(chatId, audio, [options]) ⇒ <code>Promise</code>
+### telegramBot.sendAudio(chatId, audio, [options], [fileOpts]) ⇒ <code>Promise</code>
 Send audio
 
 **Kind**: instance method of <code>[TelegramBot](#TelegramBot)</code>  
-**See**: https://core.telegram.org/bots/api#sendaudio  
+**See**
+
+- https://core.telegram.org/bots/api#sendaudio
+- https://github.com/yagop/node-telegram-bot-api/blob/master/doc/usage.md#sending-files
+
 
 | Param | Type | Description |
 | --- | --- | --- |
 | chatId | <code>Number</code> &#124; <code>String</code> | Unique identifier for the message recipient |
 | audio | <code>String</code> &#124; <code>stream.Stream</code> &#124; <code>Buffer</code> | A file path, Stream or Buffer. Can also be a `file_id` previously uploaded. |
 | [options] | <code>Object</code> | Additional Telegram query options |
+| [fileOpts] | <code>Object</code> | Optional file related meta-data |
 
 <a name="TelegramBot+sendDocument"></a>
 
@@ -371,7 +381,11 @@ Send audio
 Send Document
 
 **Kind**: instance method of <code>[TelegramBot](#TelegramBot)</code>  
-**See**: https://core.telegram.org/bots/api#sendDocument  
+**See**
+
+- https://core.telegram.org/bots/api#sendDocument
+- https://github.com/yagop/node-telegram-bot-api/blob/master/doc/usage.md#sending-files
+
 
 | Param | Type | Description |
 | --- | --- | --- |
@@ -396,46 +410,61 @@ Send .webp stickers.
 
 <a name="TelegramBot+sendVideo"></a>
 
-### telegramBot.sendVideo(chatId, video, [options]) ⇒ <code>Promise</code>
+### telegramBot.sendVideo(chatId, video, [options], [fileOpts]) ⇒ <code>Promise</code>
 Use this method to send video files, Telegram clients support mp4 videos (other formats may be sent as Document).
 
 **Kind**: instance method of <code>[TelegramBot](#TelegramBot)</code>  
-**See**: https://core.telegram.org/bots/api#sendvideo  
+**See**
+
+- https://core.telegram.org/bots/api#sendvideo
+- https://github.com/yagop/node-telegram-bot-api/blob/master/doc/usage.md#sending-files
+
 
 | Param | Type | Description |
 | --- | --- | --- |
 | chatId | <code>Number</code> &#124; <code>String</code> | Unique identifier for the message recipient |
 | video | <code>String</code> &#124; <code>stream.Stream</code> &#124; <code>Buffer</code> | A file path or Stream. Can also be a `file_id` previously uploaded. |
 | [options] | <code>Object</code> | Additional Telegram query options |
+| [fileOpts] | <code>Object</code> | Optional file related meta-data |
 
 <a name="TelegramBot+sendVideoNote"></a>
 
-### telegramBot.sendVideoNote(chatId, videoNote, [options]) ⇒ <code>Promise</code>
+### telegramBot.sendVideoNote(chatId, videoNote, [options], [fileOpts]) ⇒ <code>Promise</code>
 Use this method to send rounded square videos of upto 1 minute long.
 
 **Kind**: instance method of <code>[TelegramBot](#TelegramBot)</code>  
 **Info**: The length parameter is actually optional. However, the API (at time of writing) requires you to always provide it until it is fixed.  
-**See**: https://core.telegram.org/bots/api#sendvideonote  
+**See**
+
+- https://core.telegram.org/bots/api#sendvideonote
+- https://github.com/yagop/node-telegram-bot-api/blob/master/doc/usage.md#sending-files
+
 
 | Param | Type | Description |
 | --- | --- | --- |
 | chatId | <code>Number</code> &#124; <code>String</code> | Unique identifier for the message recipient |
 | videoNote | <code>String</code> &#124; <code>stream.Stream</code> &#124; <code>Buffer</code> | A file path or Stream. Can also be a `file_id` previously uploaded. |
 | [options] | <code>Object</code> | Additional Telegram query options |
+| [fileOpts] | <code>Object</code> | Optional file related meta-data |
 
 <a name="TelegramBot+sendVoice"></a>
 
-### telegramBot.sendVoice(chatId, voice, [options]) ⇒ <code>Promise</code>
+### telegramBot.sendVoice(chatId, voice, [options], [fileOpts]) ⇒ <code>Promise</code>
 Send voice
 
 **Kind**: instance method of <code>[TelegramBot](#TelegramBot)</code>  
-**See**: https://core.telegram.org/bots/api#sendvoice  
+**See**
+
+- https://core.telegram.org/bots/api#sendvoice
+- https://github.com/yagop/node-telegram-bot-api/blob/master/doc/usage.md#sending-files
+
 
 | Param | Type | Description |
 | --- | --- | --- |
 | chatId | <code>Number</code> &#124; <code>String</code> | Unique identifier for the message recipient |
 | voice | <code>String</code> &#124; <code>stream.Stream</code> &#124; <code>Buffer</code> | A file path, Stream or Buffer. Can also be a `file_id` previously uploaded. |
 | [options] | <code>Object</code> | Additional Telegram query options |
+| [fileOpts] | <code>Object</code> | Optional file related meta-data |
 
 <a name="TelegramBot+sendChatAction"></a>
 
diff --git a/doc/usage.md b/doc/usage.md
index 3a17700..e3499d3 100644
--- a/doc/usage.md
+++ b/doc/usage.md
@@ -115,6 +115,45 @@ const url = 'https://telegram.org/img/t_logo.png';
 bot.sendPhoto(chatId, url);
 ```
 
+If you wish to explicitly specify the filename or
+[MIME type](http://en.wikipedia.org/wiki/Internet_media_type),
+you may pass the an additional argument as file options, like so:
+
+```js
+const fileOpts = {
+  // Explicitly specify the file name.
+  filename: 'customfilename',
+  // Explicitly specify the MIME type.
+  contentType: 'audio/mpeg'
+};
+bot.sendAudio(chatId, data, {}, fileOpts);
+```
+
+<a name="sending-files-metadata"></a>
+### File Options (metadata)
+
+When sending files, the library automatically resolves
+the `filename` and `contentType` properties.
+**For now, this has to be manually activated using environment
+variable `NTBA_FIX_350`.**
+
+In order of highest-to-lowest precedence in searching for
+a value, when resolving the `filename`:
+
+1. Is `fileOptions.filename` explictly defined?
+1. Does `Stream#path` exist?
+1. Is `filepath` provided?
+1. Default to `"filename"`
+
+And the `contentType`:
+
+1. Is `fileOptions.contentType` explictly-defined?
+1. Does `Stream#path` exist?
+1. Try detecting file-type from the `Buffer`
+1. Is `filepath` provided?
+1. Is `fileOptions.filename` explicitly defined?
+1. Default to `"application/octet-stream`
+
 <a name="sending-files-performance"></a>
 ### Performance Issue
 
diff --git a/src/telegram.js b/src/telegram.js
index b69fa59..3d011bd 100644
--- a/src/telegram.js
+++ b/src/telegram.js
@@ -284,6 +284,9 @@ class TelegramBot extends EventEmitter {
    * Format data to be uploaded; handles file paths, streams and buffers
    * @param  {String} type
    * @param  {String|stream.Stream|Buffer} data
+   * @param  {Object} fileOpts File options
+   * @param  {String} [fileOpts.filename] File name
+   * @param  {String} [fileOpts.contentType] Content type (i.e. MIME)
    * @return {Array} formatted
    * @return {Object} formatted[0] formData
    * @return {String} formatted[1] fileId
@@ -291,55 +294,68 @@ class TelegramBot extends EventEmitter {
    * @see https://npmjs.com/package/file-type
    * @private
    */
-  _formatSendData(type, data) {
-    let formData;
-    let fileName;
-    let fileId;
+  _formatSendData(type, data, fileOpts = {}) {
+    let filedata = data;
+    let filename = fileOpts.filename;
+    let contentType = fileOpts.contentType;
+
     if (data instanceof stream.Stream) {
-      // Will be 'null' if could not be parsed. Default to 'filename'.
-      // For example, 'data.path' === '/?id=123' from 'request("https://example.com/?id=123")'
-      fileName = URL.parse(path.basename(data.path.toString())).pathname || 'filename';
-      formData = {};
-      formData[type] = {
-        value: data,
-        options: {
-          filename: qs.unescape(fileName),
-          contentType: mime.lookup(fileName)
-        }
-      };
+      if (!filename && data.path) {
+        // Will be 'null' if could not be parsed.
+        // For example, 'data.path' === '/?id=123' from 'request("https://example.com/?id=123")'
+        const url = URL.parse(path.basename(data.path.toString()));
+        filename = qs.unescape(url.pathname);
+      }
     } else if (Buffer.isBuffer(data)) {
-      const filetype = fileType(data);
-      if (!filetype) {
-        throw new errors.FatalError('Unsupported Buffer file type');
+      if (!filename && !process.env.NTBA_FIX_350) {
+        deprecate('Buffers will have their filenames default to "filename" instead of "data".');
+        filename = 'data';
       }
-      formData = {};
-      formData[type] = {
-        value: data,
-        options: {
-          filename: `data.${filetype.ext}`,
-          contentType: filetype.mime
+      if (!contentType) {
+        const filetype = fileType(data);
+        if (filetype) {
+          contentType = filetype.mime;
+          const ext = filetype.ext;
+          if (ext && !process.env.NTBA_FIX_350) {
+            filename = `${filename}.${ext}`;
+          }
+        } else if (!process.env.NTBA_FIX_350) {
+          deprecate('An error will no longer be thrown if file-type of buffer could not be detected.');
+          throw new errors.FatalError('Unsupported Buffer file-type');
         }
-      };
-    } else if (!this.options.filepath) {
-      /**
-       * When the constructor option 'filepath' is set to
-       * 'false', we do not support passing file-paths.
-       */
-      fileId = data;
-    } else if (fs.existsSync(data)) {
-      fileName = path.basename(data);
-      formData = {};
-      formData[type] = {
-        value: fs.createReadStream(data),
-        options: {
-          filename: fileName,
-          contentType: mime.lookup(fileName)
+      }
+    } else if (data) {
+      if (this.options.filepath && fs.existsSync(data)) {
+        filedata = fs.createReadStream(data);
+        if (!filename) {
+          filename = path.basename(data);
         }
-      };
+      } else {
+        return [null, data];
+      }
     } else {
-      fileId = data;
+      return [null, data];
     }
-    return [formData, fileId];
+
+    filename = filename || 'filename';
+    contentType = contentType || mime.lookup(filename);
+    if (process.env.NTBA_FIX_350) {
+      contentType = contentType || 'application/octet-stream';
+    } else {
+      deprecate('In the future, content-type of files you send will default to "application/octet-stream".');
+    }
+
+    // TODO: Add missing file extension.
+
+    return [{
+      [type]: {
+        value: filedata,
+        options: {
+          filename,
+          contentType,
+        },
+      },
+    }, null];
   }
 
   /**
@@ -685,16 +701,18 @@ class TelegramBot extends EventEmitter {
    * @param  {String|stream.Stream|Buffer} photo A file path or a Stream. Can
    * also be a `file_id` previously uploaded
    * @param  {Object} [options] Additional Telegram query options
+   * @param  {Object} [fileOpts] Optional file related meta-data
    * @return {Promise}
    * @see https://core.telegram.org/bots/api#sendphoto
+   * @see https://github.com/yagop/node-telegram-bot-api/blob/master/doc/usage.md#sending-files
    */
-  sendPhoto(chatId, photo, options = {}) {
+  sendPhoto(chatId, photo, options = {}, fileOpts = {}) {
     const opts = {
       qs: options,
     };
     opts.qs.chat_id = chatId;
     try {
-      const sendData = this._formatSendData('photo', photo);
+      const sendData = this._formatSendData('photo', photo, fileOpts);
       opts.formData = sendData[0];
       opts.qs.photo = sendData[1];
     } catch (ex) {
@@ -709,16 +727,18 @@ class TelegramBot extends EventEmitter {
    * @param  {String|stream.Stream|Buffer} audio A file path, Stream or Buffer.
    * Can also be a `file_id` previously uploaded.
    * @param  {Object} [options] Additional Telegram query options
+   * @param  {Object} [fileOpts] Optional file related meta-data
    * @return {Promise}
    * @see https://core.telegram.org/bots/api#sendaudio
+   * @see https://github.com/yagop/node-telegram-bot-api/blob/master/doc/usage.md#sending-files
    */
-  sendAudio(chatId, audio, options = {}) {
+  sendAudio(chatId, audio, options = {}, fileOpts = {}) {
     const opts = {
       qs: options
     };
     opts.qs.chat_id = chatId;
     try {
-      const sendData = this._formatSendData('audio', audio);
+      const sendData = this._formatSendData('audio', audio, fileOpts);
       opts.formData = sendData[0];
       opts.qs.audio = sendData[1];
     } catch (ex) {
@@ -736,6 +756,7 @@ class TelegramBot extends EventEmitter {
    * @param  {Object} [fileOpts] Optional file related meta-data
    * @return {Promise}
    * @see https://core.telegram.org/bots/api#sendDocument
+   * @see https://github.com/yagop/node-telegram-bot-api/blob/master/doc/usage.md#sending-files
    */
   sendDocument(chatId, doc, options = {}, fileOpts = {}) {
     const opts = {
@@ -743,15 +764,12 @@ class TelegramBot extends EventEmitter {
     };
     opts.qs.chat_id = chatId;
     try {
-      const sendData = this._formatSendData('document', doc);
+      const sendData = this._formatSendData('document', doc, fileOpts);
       opts.formData = sendData[0];
       opts.qs.document = sendData[1];
     } catch (ex) {
       return Promise.reject(ex);
     }
-    if (opts.formData && Object.keys(fileOpts).length) {
-      opts.formData.document.options = fileOpts;
-    }
     return this._request('sendDocument', opts);
   }
 
@@ -785,16 +803,18 @@ class TelegramBot extends EventEmitter {
    * @param  {String|stream.Stream|Buffer} video A file path or Stream.
    * Can also be a `file_id` previously uploaded.
    * @param  {Object} [options] Additional Telegram query options
+   * @param  {Object} [fileOpts] Optional file related meta-data
    * @return {Promise}
    * @see https://core.telegram.org/bots/api#sendvideo
+   * @see https://github.com/yagop/node-telegram-bot-api/blob/master/doc/usage.md#sending-files
    */
-  sendVideo(chatId, video, options = {}) {
+  sendVideo(chatId, video, options = {}, fileOpts = {}) {
     const opts = {
       qs: options
     };
     opts.qs.chat_id = chatId;
     try {
-      const sendData = this._formatSendData('video', video);
+      const sendData = this._formatSendData('video', video, fileOpts);
       opts.formData = sendData[0];
       opts.qs.video = sendData[1];
     } catch (ex) {
@@ -809,17 +829,19 @@ class TelegramBot extends EventEmitter {
    * @param  {String|stream.Stream|Buffer} videoNote A file path or Stream.
    * Can also be a `file_id` previously uploaded.
    * @param  {Object} [options] Additional Telegram query options
+   * @param  {Object} [fileOpts] Optional file related meta-data
    * @return {Promise}
    * @info The length parameter is actually optional. However, the API (at time of writing) requires you to always provide it until it is fixed.
    * @see https://core.telegram.org/bots/api#sendvideonote
+   * @see https://github.com/yagop/node-telegram-bot-api/blob/master/doc/usage.md#sending-files
    */
-  sendVideoNote(chatId, videoNote, options = {}) {
+  sendVideoNote(chatId, videoNote, options = {}, fileOpts = {}) {
     const opts = {
       qs: options
     };
     opts.qs.chat_id = chatId;
     try {
-      const sendData = this._formatSendData('video_note', videoNote);
+      const sendData = this._formatSendData('video_note', videoNote, fileOpts);
       opts.formData = sendData[0];
       opts.qs.video_note = sendData[1];
     } catch (ex) {
@@ -834,16 +856,18 @@ class TelegramBot extends EventEmitter {
    * @param  {String|stream.Stream|Buffer} voice A file path, Stream or Buffer.
    * Can also be a `file_id` previously uploaded.
    * @param  {Object} [options] Additional Telegram query options
+   * @param  {Object} [fileOpts] Optional file related meta-data
    * @return {Promise}
    * @see https://core.telegram.org/bots/api#sendvoice
+   * @see https://github.com/yagop/node-telegram-bot-api/blob/master/doc/usage.md#sending-files
    */
-  sendVoice(chatId, voice, options = {}) {
+  sendVoice(chatId, voice, options = {}, fileOpts = {}) {
     const opts = {
       qs: options
     };
     opts.qs.chat_id = chatId;
     try {
-      const sendData = this._formatSendData('voice', voice);
+      const sendData = this._formatSendData('voice', voice, fileOpts);
       opts.formData = sendData[0];
       opts.qs.voice = sendData[1];
     } catch (ex) {
diff --git a/test/telegram.js b/test/telegram.js
index b300ab2..c0501cf 100644
--- a/test/telegram.js
+++ b/test/telegram.js
@@ -630,13 +630,6 @@ describe('TelegramBot', function telegramSuite() {
         assert.ok(is.object(resp.document));
       });
     });
-    it('should send a document with custom file options', function test() {
-      const document = fs.createReadStream(`${__dirname}/data/photo.gif`);
-      const fileOpts = { filename: 'customfilename.gif' };
-      return bot.sendDocument(USERID, document, {}, fileOpts).then(resp => {
-        assert.equal(resp.document.file_name, fileOpts.filename);
-      });
-    });
   });
 
   describe('#sendSticker', function sendStickerSuite() {
diff --git a/test/test.sendfile.js b/test/test.sendfile.js
new file mode 100644
index 0000000..864d900
--- /dev/null
+++ b/test/test.sendfile.js
@@ -0,0 +1,109 @@
+const assert = require('assert');
+const fs = require('fs');
+const path = require('path');
+const TelegramBot = require('..');
+
+const paths = {
+  audio: path.join(__dirname, "data/audio.mp3"),
+};
+
+
+// TODO:Enable all other tests
+describe.only('sending files', function sendfileSuite() {
+  const bot = new TelegramBot("token");
+
+  before(function beforeSuite() {
+    process.env.NTBA_FIX_350 = 1;
+  });
+  after(function afterSuite() {
+    delete process.env.NTBA_FIX_350;
+  });
+
+  describe('using fileOptions', function sendfileOptionsSuite() {
+    const type = 'file';
+    const stream = fs.createReadStream(paths.audio);
+    const nonPathStream = fs.createReadStream(paths.audio);
+    const buffer = fs.readFileSync(paths.audio);
+    const nonDetectableBuffer = fs.readFileSync(__filename);
+    const filepath = paths.audio;
+    const fileId = 'fileId';
+    const files = [stream, nonPathStream, buffer, nonDetectableBuffer, filepath];
+
+    delete nonPathStream.path;
+
+    describe('filename', function filenameSuite() {
+      it('(1) fileOptions.filename', function test() {
+        const filename = 'custom-filename';
+        files.forEach((file) => {
+          const [{ [type]: data }] = bot._formatSendData(type, file, { filename });
+          assert.equal(data.options.filename, filename);
+        });
+      });
+
+      it('(2) Stream#path', function test() {
+        if (!stream.path) {
+          return this.skip('Stream#path unsupported');
+        }
+        const [{ [type]: data }] = bot._formatSendData(type, stream);
+        assert.equal(data.options.filename, path.basename(paths.audio));
+      });
+
+      it('(3) filepath', function test() {
+        const [{ [type]: data }] = bot._formatSendData(type, filepath);
+        assert.equal(data.options.filename, path.basename(paths.audio));
+      });
+
+      it('(4) final default', function test() {
+        [nonPathStream, buffer, nonDetectableBuffer].forEach((file) => {
+          const [{ [type]: data }] = bot._formatSendData(type, file);
+          assert.equal(data.options.filename, 'filename');
+        });
+      });
+    });
+
+    describe('contentType', function contentTypeSuite() {
+      it('(1) fileOpts.contentType', function test() {
+        const contentType = 'application/custom-type';
+        files.forEach((file) => {
+          const [{ [type]: data }] = bot._formatSendData(type, file, { contentType });
+          assert.equal(data.options.contentType, contentType);
+        });
+      });
+
+      it('(2) Stream#path', function test() {
+        if (!stream.path) {
+          return this.skip('Stream#path unsupported');
+        }
+        const [{ [type]: data }] = bot._formatSendData(type, stream);
+        assert.equal(data.options.contentType, 'audio/mpeg');
+      });
+
+      it('(3) Buffer file-type', function test() {
+        const [{ [type]: data }] = bot._formatSendData(type, buffer);
+        assert.equal(data.options.contentType, 'audio/mpeg');
+      });
+
+      it('(4) filepath', function test() {
+        const [{ [type]: data }] = bot._formatSendData(type, filepath);
+        assert.equal(data.options.contentType, 'audio/mpeg');
+      });
+
+      it('(5) fileOptions.filename', function test() {
+        [nonPathStream, nonDetectableBuffer].forEach((file) => {
+          const [{ [type]: data }] = bot._formatSendData(type, file, {
+            filename: 'image.gif',
+          });
+          assert.equal(data.options.contentType, 'image/gif');
+        });
+      });
+
+      it('(6) Final default', function test() {
+        [nonPathStream, nonDetectableBuffer].forEach((file) => {
+          const [{ [type]: data }] = bot._formatSendData(type, file);
+          assert.equal(data.options.contentType, 'application/octet-stream');
+        });
+      });
+    });
+
+  });
+});