diff --git a/test_ffmpeg_concat_command.py b/test_ffmpeg_concat_command.py
new file mode 100644
index 0000000..daa5d69
--- /dev/null
+++ b/test_ffmpeg_concat_command.py
@@ -0,0 +1,106 @@
+import shutil
+from pathlib import Path
+import tempfile
+import unittest
+from unittest.mock import MagicMock
+
+from segment import Segment
+from shell_command import FFmpegConcatCommand
+from test_shared import ShellCommandSharedTestCase
+
+
+class FFmpegConcatCommandTestCase(ShellCommandSharedTestCase):
+    """Test the FFmpegConcatCommand class."""
+
+    # What about testing different permutations of audio and video?
+    def setUp(self):
+        """Set up for test."""
+        # Make sure the input and output options are explicitly set,
+        # otherwise they hang around from previous tests.
+        self.command = FFmpegConcatCommand(
+            input_options=["-i", "in.mov"], output_options=["out.mov"],
+            has_video=True, has_audio=True, quiet=True)
+        self.expected_executable = shutil.which("ffmpeg")
+        self.expected_base_options = ["-y", "-nostdin",]
+        self.expected_input_options = ["-i", "in.mov"]
+        self.expected_filter_options = ["-filter_complex", ""]
+        self.expected_output_options = [
+            "-codec:a", self.command.audio_codec,
+            "-ac", "1",
+            "-map", "[anorm]",
+            "-codec:v", self.command.video_codec,
+            "-pix_fmt", "yuv420p",
+            "-map", "[vconc]",
+            "out.mov"
+        ]
+
+    def tearDown(self):
+        """Clean up after test."""
+        self.command = None
+    
+    def test_append_filter(self):
+        """Test appending to the filter list."""
+        # append empty filter => no change
+        with self.subTest(msg="empty"):
+            filters = []
+            self.command.append_filter("")
+            self.assertEqual(self.command.filters, filters)
+        # append an actual filter
+        with self.subTest(msg="normal"):
+            filters = ["this_is_a_weird_filter"]
+            self.command.append_filter("this_is_a_weird_filter")
+            self.assertEqual(self.command.filters, filters)
+    
+    def test_append_normalisation_filter(self):
+        """Test appending a normalisation filter."""
+        filters = ["[aconc] dynaudnorm=r=0.25:f=10:b=y [anorm]"]
+        self.command.append_normalisation_filter()
+        self.assertEqual(self.command.filters, filters)
+    
+    def test_append_concat_filter_0(self):
+        """Test appending a concat filter with no segments."""
+        self.command.append_concat_filter(type="a", segments=[])
+        with self.subTest(msg="audio"):
+            self.assertEqual(self.command.filters, [])
+        self.command.append_concat_filter(type="v", segments=[])
+        with self.subTest(msg="video"):
+            self.assertEqual(self.command.filters, [])
+        self.command.append_concat_filter(type="f", segments=[])
+        with self.subTest(msg="frame"):
+            self.assertEqual(self.command.filters, [])
+    
+    def test_append_concat_filter_f(self):
+        """Test appending a concat filter with a frame segment."""
+        self.command.append_concat_filter(type="f", segments=[Segment()])
+        self.assertEqual(
+            self.command.filters, [],
+            msg="frame segments should be ignored")
+    
+    # def test_append_concat_filter_1_a(self):
+    #     """Test appending a concat filter with 1 audio segment."""
+    #     self.command.append_concat_filter(
+    #         type="a",
+    #         segments=[Segment(file="a.mov", punch_in=10,
+    #                   punch_out=20, input_stream=1)])
+    #     with self.subTest(msg="audio"):
+    #         self.assertEqual(self.command.filters, [])
+    
+    # def test_append_concat_filter_1_v(self):
+    #     """Test appending a concat filter with 1 video segment."""
+    #     concat = 
+    #     self.command.append_concat_filter(type="v",
+    #         segments=[Segment(file="v.mov", punch_in=10,
+    #             punch_out=20, input_stream=1)])
+    #     with self.subTest(msg="audio"):
+    #         self.assertEqual()
+    
+    # def test_append_concat_filter_2(self):
+    #     """Test appending a concat filter with >1 segment."""
+    
+    # def test_build_complex_filter(self):
+    #     """Test building the complex filter."""
+
+
+# Remove ShellCommandSharedTestCase from the namespace so we don't run
+# the shared tests twice. See <https://stackoverflow.com/a/22836015>.
+del(ShellCommandSharedTestCase)