diff --git a/tests/test_utils.py b/tests/test_utils.py
new file mode 100644
index 0000000..fdd5114
--- /dev/null
+++ b/tests/test_utils.py
@@ -0,0 +1,33 @@
+import unittest
+import re
+
+# Add relative pygcode to path
+from testutils import add_pygcode_to_path, str_lines
+add_pygcode_to_path()
+
+# Units under test
+from pygcode.utils import omit_redundant_modes
+from pygcode import text2gcodes, Line
+
+class UtilityTests(unittest.TestCase):
+    def test_omit_redundant_modes(self):
+        lines = [
+            Line(line_str)
+            for line_str in re.split(r'\s*\n\s*', '''
+                g1 x0 y0 ; yes
+                g1 x10 y-20 ; no
+                g0 x-3 y2 ; yes
+                g0 x0 y0 ; no
+                g0 x1 y1 ; no
+                g1 x20 y20 z5 ; yes
+            ''')
+            if line_str
+        ]
+        gcodes = [l.gcodes[0] for l in lines]
+        comments = [l.comment for l in lines]
+        for (i, g) in enumerate(omit_redundant_modes(gcodes)):
+            comment = comments[i].text if comments[i] else None
+            if comment == 'no':
+                self.assertIsNotNone(re.search(r'^\s', str(g)))
+            elif comment == 'yes':
+                self.assertIsNone(re.search(r'^\s', str(g)))