diff --git a/translate_lyrics/test_translate_lyrics.py b/translate_lyrics/test_translate_lyrics.py
index 63976f9..4547297 100644
--- a/translate_lyrics/test_translate_lyrics.py
+++ b/translate_lyrics/test_translate_lyrics.py
@@ -3,6 +3,15 @@
 from unittest import mock
 
 
+class MockResponse:
+    def __init__(self, json_data, status_code):
+        self.json_data = json_data
+        self.status_code = status_code
+
+    def json(self):
+        return self.json_data
+
+
 def mock_requests_post(*args, **kwargs):
     """
     Mock patch request.post() calls
@@ -10,13 +19,6 @@ def mock_requests_post(*args, **kwargs):
     @param kwargs:
     @return:
     """
-    class MockResponse:
-        def __init__(self, json_data, status_code):
-            self.json_data = json_data
-            self.status_code = status_code
-
-        def json(self):
-            return self.json_data
 
     # TODO: improve this url detection
     if args[0].startswith("https://api.cognitive.microsofttranslator.com/"):
@@ -33,6 +35,20 @@ def json(self):
     return MockResponse(None, 404)
 
 
+def mock_requests_post_invalid(*args, **kwargs):
+    """
+    Mock patch request.post() calls
+    @param args:
+    @param kwargs:
+    @return:
+    """
+    return MockResponse([
+        {
+            "fake_bad_data": "bad"
+        }
+    ], 200)
+
+
 def test_translate_lyrics_sets_translator_key():
     """
     Sets translator key
@@ -43,7 +59,7 @@ def test_translate_lyrics_sets_translator_key():
 
 
 @mock.patch('requests.post', side_effect=mock_requests_post)
-def test_translate_lyrics(mock_requests_post):
+def test_translate_lyrics(mock_req):
     """
     Translates lyrics
     """
@@ -59,11 +75,42 @@ def test_translate_lyrics(mock_requests_post):
     # assert it replies with the mocked translated lyrics
     assert english_translation == "mocked translated lyrics"
 
+
+@mock.patch('requests.post', side_effect=mock_requests_post_invalid)
+def test_translate_lyrics_invalid(mock_req):
+    """
+    Translates lyrics
+    """
+
+    # Prepare: instantiate TranslateLyrics with fake translator key
+    translator_key = "fake_translator_key"
+    translate_lyrics_obj = TranslateLyrics(translator_key)
+
+    # mock_requests_post returns a mocked response from "https://api.cognitive.microsofttranslator.com/"
+    # call translate_lyrics_obj.translate_lyrics(lyrics)
+    english_translation = translate_lyrics_obj.translate_lyrics("some lyrics")
+
+    # assert it replies with the mocked translated lyrics
+    assert english_translation == ""
+
+
 @mock.patch('requests.post', side_effect=mock_requests_post)
-def test_mock_requests_post_404(mock_requests_post):
+def test_mock_requests_post_404(mock_req):
     """
     Test 404
     """
 
     resp = requests.post("https://example.com/404")
     assert resp.status_code == 404
+
+
+@mock.patch('requests.post', side_effect=mock_requests_post_invalid)
+def test_mock_requests_post_invalid(mock_req):
+    """
+    Test 404
+    """
+
+    resp = requests.post("https://example.com/404")
+    resp_json = resp.json()
+    assert resp_json[0]["fake_bad_data"] == "bad"
+    assert resp.status_code == 200