diff --git a/updater_sample/tools/gen_update_config.py b/updater_sample/tools/gen_update_config.py
index 0578124..4efa9f1 100755
--- a/updater_sample/tools/gen_update_config.py
+++ b/updater_sample/tools/gen_update_config.py
@@ -17,11 +17,13 @@
 """
 Given a OTA package file, produces update config JSON file.
 
-Example:  tools/gen_update_config.py \\
-            --ab_install_type=STREAMING \\
-            ota-build-001.zip  \\
-            my-config-001.json \\
-            http://foo.bar/ota-builds/ota-build-001.zip
+Example:
+      $ PYTHONPATH=$ANDROID_BUILD_TOP/build/make/tools/releasetools:$PYTHONPATH \\
+            bootable/recovery/updater_sample/tools/gen_update_config.py \\
+                --ab_install_type=STREAMING \\
+                ota-build-001.zip  \\
+                my-config-001.json \\
+                http://foo.bar/ota-builds/ota-build-001.zip
 """
 
 import argparse
@@ -30,6 +32,8 @@
 import sys
 import zipfile
 
+import ota_from_target_files  # pylint: disable=import-error
+
 
 class GenUpdateConfig(object):
     """
@@ -41,7 +45,6 @@
 
     AB_INSTALL_TYPE_STREAMING = 'STREAMING'
     AB_INSTALL_TYPE_NON_STREAMING = 'NON_STREAMING'
-    METADATA_NAME = 'META-INF/com/android/metadata'
 
     def __init__(self, package, url, ab_install_type):
         self.package = package
@@ -82,37 +85,27 @@
     def _gen_ab_streaming_metadata(self):
         """Builds metadata for files required for streaming update."""
         with zipfile.ZipFile(self.package, 'r') as package_zip:
-            property_files = self._get_property_files(package_zip)
-
             metadata = {
-                'property_files': property_files
+                'property_files': self._get_property_files(package_zip)
             }
 
         return metadata
 
-    def _get_property_files(self, zip_file):
+    @staticmethod
+    def _get_property_files(package_zip):
         """Constructs the property-files list for A/B streaming metadata."""
 
-        def compute_entry_offset_size(name):
-            """Computes the zip entry offset and size."""
-            info = zip_file.getinfo(name)
-            offset = info.header_offset + len(info.FileHeader())
-            size = info.file_size
-            return {
-                'filename': os.path.basename(name),
-                'offset': offset,
-                'size': size,
-            }
-
+        ab_ota = ota_from_target_files.AbOtaPropertyFiles()
+        property_str = ab_ota.GetPropertyFilesString(package_zip, False)
         property_files = []
-        for entry in self.streaming_required:
-            property_files.append(compute_entry_offset_size(entry))
-        for entry in self.streaming_optional:
-            if entry in zip_file.namelist():
-                property_files.append(compute_entry_offset_size(entry))
-
-        # 'META-INF/com/android/metadata' is required
-        property_files.append(compute_entry_offset_size(GenUpdateConfig.METADATA_NAME))
+        for file in property_str.split(','):
+            filename, offset, size = file.split(':')
+            inner_file = {
+                'filename': filename,
+                'offset': int(offset),
+                'size': int(size)
+            }
+            property_files.append(inner_file)
 
         return property_files
 
diff --git a/updater_sample/tools/gen_update_config_test.py b/updater_sample/tools/test_gen_update_config.py
similarity index 69%
rename from updater_sample/tools/gen_update_config_test.py
rename to updater_sample/tools/test_gen_update_config.py
index 951d4c4..c907cf2 100755
--- a/updater_sample/tools/gen_update_config_test.py
+++ b/updater_sample/tools/test_gen_update_config.py
@@ -15,7 +15,11 @@
 # limitations under the License.
 
 """
-Tests gen_update_config.py
+Tests gen_update_config.py.
+
+Example:
+    $ PYTHONPATH=$ANDROID_BUILD_TOP/build/make/tools/releasetools:$PYTHONPATH \\
+        python3 -m unittest test_gen_update_config
 """
 
 import os.path
@@ -29,15 +33,21 @@
         """tests if streaming property files' offset and size are generated properly"""
         config, package = self._generate_config()
         property_files = config['ab_streaming_metadata']['property_files']
-        self.assertEqual(len(property_files), 5)
+        self.assertEqual(len(property_files), 6)
         with open(package, 'rb') as pkg_file:
             for prop in property_files:
                 filename, offset, size = prop['filename'], prop['offset'], prop['size']
                 pkg_file.seek(offset)
-                data = pkg_file.read(size).decode('ascii')
-                # data in the archive are just uppercase filenames without extension
-                expected_data = filename.split('.')[0].upper()
-                self.assertEqual(data, expected_data)
+                raw_data = pkg_file.read(size)
+                if filename in ['payload.bin', 'payload_metadata.bin']:
+                    pass
+                elif filename == 'payload_properties.txt':
+                    pass
+                elif filename == 'metadata':
+                    self.assertEqual(raw_data.decode('ascii'), 'META-INF/COM/ANDROID/METADATA')
+                else:
+                    expected_data = filename.replace('.', '-').upper()
+                    self.assertEqual(raw_data.decode('ascii'), expected_data)
 
     @staticmethod
     def _generate_config():
@@ -49,7 +59,3 @@
                               GenUpdateConfig.AB_INSTALL_TYPE_STREAMING)
         gen.run()
         return gen.config, ota_package
-
-
-if __name__ == '__main__':
-    unittest.main()