diff --git a/scripts/manifest_fixer_test.py b/scripts/manifest_fixer_test.py
index f6fcaaf..199b279 100755
--- a/scripts/manifest_fixer_test.py
+++ b/scripts/manifest_fixer_test.py
@@ -521,12 +521,55 @@
     self.assert_xml_equal(output, manifest_input)
 
   def test_has_application_has_code_true(self):
-    """ Do nothing if there's already an application elemeent even if its
+    """ Do nothing if there's already an application element even if its
      hasCode attribute is true. """
     manifest_input = self.manifest_tmpl % '    <application android:hasCode="true"/>\n'
     output = self.run_test(manifest_input)
     self.assert_xml_equal(output, manifest_input)
 
 
+class AddTestOnlyApplicationTest(unittest.TestCase):
+  """Unit tests for set_test_only_flag_to_true function."""
+
+  def assert_xml_equal(self, output, expected):
+    self.assertEqual(ET.canonicalize(output), ET.canonicalize(expected))
+
+  def run_test(self, input_manifest):
+    doc = minidom.parseString(input_manifest)
+    manifest_fixer.set_test_only_flag_to_true(doc)
+    output = io.StringIO()
+    manifest_fixer.write_xml(output, doc)
+    return output.getvalue()
+
+  manifest_tmpl = (
+      '<?xml version="1.0" encoding="utf-8"?>\n'
+      '<manifest xmlns:android="http://schemas.android.com/apk/res/android">\n'
+      '%s'
+      '</manifest>\n')
+
+  def test_no_application(self):
+    manifest_input = self.manifest_tmpl % ''
+    expected = self.manifest_tmpl % '    <application android:testOnly="true"/>\n'
+    output = self.run_test(manifest_input)
+    self.assert_xml_equal(output, expected)
+
+  def test_has_application_no_test_only(self):
+    manifest_input = self.manifest_tmpl % '    <application/>\n'
+    expected = self.manifest_tmpl % '    <application android:testOnly="true"/>\n'
+    output = self.run_test(manifest_input)
+    self.assert_xml_equal(output, expected)
+
+  def test_has_application_test_only_true(self):
+    """ If there's already an application element."""
+    manifest_input = self.manifest_tmpl % '    <application android:testOnly="true"/>\n'
+    output = self.run_test(manifest_input)
+    self.assert_xml_equal(output, manifest_input)
+
+  def test_has_application_test_only_false(self):
+    """ If there's already an application element with the testOnly attribute as false."""
+    manifest_input = self.manifest_tmpl % '    <application android:testOnly="false"/>\n'
+    output = self.run_test(manifest_input)
+    self.assert_xml_equal(output, manifest_input)
+
 if __name__ == '__main__':
   unittest.main(verbosity=2)