diff --git a/testing/raptor/test/python.ini b/testing/raptor/test/python.ini
index 64094a625f9cc..d6627efffffa0 100644
--- a/testing/raptor/test/python.ini
+++ b/testing/raptor/test/python.ini
@@ -5,5 +5,6 @@ skip-if = python == 3
 [test_cmdline.py]
 [test_manifest.py]
 [test_control_server.py]
+[test_utils.py]
 [test_playback.py]
 [test_raptor.py]
diff --git a/testing/raptor/test/test_utils.py b/testing/raptor/test/test_utils.py
new file mode 100644
index 0000000000000..eda01af23539f
--- /dev/null
+++ b/testing/raptor/test/test_utils.py
@@ -0,0 +1,48 @@
+from __future__ import absolute_import, unicode_literals
+
+import mozunit
+import os
+import pytest
+import sys
+
+# need this so raptor imports work both from /raptor and via mach
+here = os.path.abspath(os.path.dirname(__file__))
+if os.environ.get('SCRIPTSPATH', None) is not None:
+    # in production it is env SCRIPTS_PATH
+    mozharness_dir = os.environ['SCRIPTSPATH']
+else:
+    # locally it's in source tree
+    mozharness_dir = os.path.join(here, '../../mozharness')
+sys.path.insert(1, mozharness_dir)
+
+raptor_dir = os.path.join(os.path.dirname(here), 'raptor')
+sys.path.insert(0, raptor_dir)
+
+from utils import transform_platform
+
+
+@pytest.mark.parametrize('platform', ['win', 'mac', 'linux64'])
+def test_transform_platform(platform):
+    transformed = transform_platform("mitmproxy-rel-bin-{platform}.manifest", platform)
+    assert "{platform}" not in transformed
+    if platform == 'mac':
+        assert "osx" in transformed
+    else:
+        assert platform in transformed
+
+
+def test_transform_platform_no_change():
+    starting_string = "nothing-in-here-to-transform"
+    assert transform_platform(starting_string, 'mac') == starting_string
+
+
+@pytest.mark.parametrize('processor', ['x86_64', 'other'])
+def test_transform_platform_processor(processor):
+    transformed = transform_platform("string-with-processor-{x64}.manifest", 'win', processor)
+    assert "{x64}" not in transformed
+    if processor == 'x86_64':
+        assert "_x64" in transformed
+
+
+if __name__ == '__main__':
+    mozunit.main()