diff --git a/src/test_pamhyr.py b/src/test_pamhyr.py
index 32ec8cd6f25eecdc8d40ade9508494b10d5d34cc..7066a65382e29440de2380eb7c87b2634c6e4a79 100644
--- a/src/test_pamhyr.py
+++ b/src/test_pamhyr.py
@@ -20,7 +20,69 @@ import os
 import unittest
 import tempfile
 
-from tools import parse_command_line
+from tools import flatten, parse_command_line
+
+
+class FlattenTestCase(unittest.TestCase):
+    def test_flatten_0(self):
+        input = []
+        output = []
+
+        res = flatten(input)
+
+        self.assertEqual(len(res), len(output))
+        for i, o in enumerate(output):
+            self.assertEqual(res[i], o)
+
+    def test_flatten_1(self):
+        input = [['foo']]
+        output = ['foo']
+
+        res = flatten(input)
+
+        self.assertEqual(len(res), len(output))
+        for i, o in enumerate(output):
+            self.assertEqual(res[i], o)
+
+    def test_flatten_2(self):
+        input = [['foo', 'bar']]
+        output = ['foo', 'bar']
+
+        res = flatten(input)
+
+        self.assertEqual(len(res), len(output))
+        for i, o in enumerate(output):
+            self.assertEqual(res[i], o)
+
+    def test_flatten_3(self):
+        input = [['foo'], ['bar']]
+        output = ['foo', 'bar']
+
+        res = flatten(input)
+
+        self.assertEqual(len(res), len(output))
+        for i, o in enumerate(output):
+            self.assertEqual(res[i], o)
+
+    def test_flatten_4(self):
+        input = [['foo'], ['bar', 'baz'], ['bazz']]
+        output = ['foo', 'bar', 'baz', 'bazz']
+
+        res = flatten(input)
+
+        self.assertEqual(len(res), len(output))
+        for i, o in enumerate(output):
+            self.assertEqual(res[i], o)
+
+    def test_flatten_5(self):
+        input = [['foo'], ['bar', ['baz']], ['bazz']]
+        output = ['foo', 'bar', ['baz'], 'bazz']
+
+        res = flatten(input)
+
+        self.assertEqual(len(res), len(output))
+        for i, o in enumerate(output):
+            self.assertEqual(res[i], o)
 
 
 class ToolsCMDParserTestCase(unittest.TestCase):