diff --git a/test/test_producers.py b/test/test_producers.py
index c95e706..7d5f057 100644
--- a/test/test_producers.py
+++ b/test/test_producers.py
@@ -1,18 +1,16 @@
 """test_producers.py -- test the producers in the pipeline (eg ffmpeg, visualisation, json)"""
 import unittest
 import pipeline.video_producers as producers
+import test.mocks as mocks
 
 
-class MockFeature():
-    """Mock feature object for testing JSONProducer"""
-    def __init__(self, interval):
-        self.interval = interval
-    def to_json(self):
-        return {"interval": self.interval}
-
 class TestFfmpegVideoProducer(unittest.TestCase):
     """Test FfmpegVideoProducer (produces videos using ffmpeg)"""
 
+    def mock_run_no_output(self, cmd, cwd="."):
+        """Mock out _run_no_output"""
+        return None
+
     def test_init_empty(self):
         # test with no features -- should raise ValueError
         with self.assertRaises(ValueError):
@@ -20,23 +18,40 @@ class TestFfmpegVideoProducer(unittest.TestCase):
 
     def test_init(self):
         # test with features
-        feature = MockFeature(interval="")
+        feature = mocks.MockFeature(interval="")
         features = [feature]
         vidprod = producers.FfmpegVideoProducer(features=features)
         self.assertEqual(vidprod.features, features)
 
     def test_ffmpeg_feature_to_clip(self):
-        # TODO
-        pass
+        """Test without a feature and without output path -- unhappy path"""
+        feature = mocks.MockFeature(interval=mocks.MockInterval(start=0, end=5),
+                              source=mocks.MockSource(path="test.mp4"))
+        features = [feature]
+        vidprod = producers.FfmpegVideoProducer(features=features)
+        with self.assertRaises(ValueError):
+            vidprod._ffmpeg_feature_to_clip(feature=None)
+        with self.assertRaises(ValueError):
+            vidprod._ffmpeg_feature_to_clip(feature=feature, output_filepath=None)
 
     def test_ffmpeg_concat_clips(self):
-        # TODO
-        pass
+        """Test without clips and without output path -- unhappy path"""
+        feature = mocks.MockFeature(interval="")
+        features = [feature]
+        vidprod = producers.FfmpegVideoProducer(features=features)
+        with self.assertRaises(ValueError):
+            vidprod._ffmpeg_concat_clips(clips=None)
+        with self.assertRaises(ValueError):
+            vidprod._ffmpeg_concat_clips(clips=features, output_filepath=None)
 
+    # happy path
     def test_produce(self):
         """Test we can call produce without error"""
-        # TODO
-        pass
+        feature = mocks.MockFeature(interval=mocks.MockInterval(start=0, end=5),
+                              source=mocks.MockSource(path="test.mp4"))
+        features = [feature]
+        vidprod = producers.FfmpegVideoProducer(features=features)
+        vidprod.produce()
 
 class TestVisualisationProducer(unittest.TestCase):
     """Test VisualisationProducer (produces matplotlib visualisations)"""
@@ -48,7 +63,7 @@ class TestVisualisationProducer(unittest.TestCase):
 
     def test_init(self):
         # test with features
-        feature = MockFeature(interval="")
+        feature = mocks.MockFeature(interval="")
         features = [feature]
         visprod = producers.VisualisationProducer(features=features)
         self.assertEqual(visprod.features, features)
@@ -66,15 +81,23 @@ class TestJSONProducer(unittest.TestCase):
 
     def test_init(self):
         # test with features
-        feature = MockFeature(interval="")
+        feature = mocks.MockFeature(interval="")
         features = [feature]
         jsonprod = producers.JSONProducer(features=features)
         self.assertEqual(jsonprod.features, features)
 
     def test_produce(self):
         """Test we can call produce without error"""
-        feature = MockFeature(interval="")
+        feature = mocks.MockFeature(interval="")
         features = [feature]
         jsonprod = producers.JSONProducer(features=features)
         jsonprod.produce()
 
+class TestPipelineJSONEncoder(unittest.TestCase):
+    """Test PipelineJSONEncoder"""
+    # unhappy path
+
+    def test_default_unserializable(self):
+        pje = producers.PipelineJSONEncoder()
+        with self.assertRaises(TypeError):
+            pje.default(object())