Add more tests to please Coveralls

tests/test_s3/test_s3.py

@@ -70,12 +70,46 @@ class MyModel(object):
 def test_keys_are_pickleable():
     """Keys must be pickleable due to boto3 implementation details."""
     key = s3model.FakeKey('name', b'data!')
+    assert key.value == b'data!'
+
     pickled = pickle.dumps(key)
     loaded = pickle.loads(pickled)
-
     assert loaded.value == key.value
 
 
+@mock_s3
+def test_append_to_value__basic():
+    key = s3model.FakeKey('name', b'data!')
+    assert key.value == b'data!'
+    assert key.size == 5
+
+    key.append_to_value(b' And even more data')
+    assert key.value == b'data! And even more data'
+    assert key.size == 24
+
+
+@mock_s3
+def test_append_to_value__nothing_added():
+    key = s3model.FakeKey('name', b'data!')
+    assert key.value == b'data!'
+    assert key.size == 5
+
+    key.append_to_value(b'')
+    assert key.value == b'data!'
+    assert key.size == 5
+
+
+@mock_s3
+def test_append_to_value__empty_key():
+    key = s3model.FakeKey('name', b'')
+    assert key.value == b''
+    assert key.size == 0
+
+    key.append_to_value(b'stuff')
+    assert key.value == b'stuff'
+    assert key.size == 5
+
+
 @mock_s3
 def test_my_model_save():
     # Create Bucket so that test can run