Make the summary file path more accessible. (#865)

This file is the entry point of all result parsing. We make this path
clear so the upper layer systems don't have to calculate it with
assumptions that may change implicitly.

mobly/test_runner.py

@@ -252,6 +252,10 @@ def generate_test_run_log_path(self):
                                            self._logger_start_time)
       return self.root_output_path
 
+    @property
+    def summary_file_path(self):
+      return os.path.join(self.root_output_path, records.OUTPUT_FILE_SUMMARY)
+
     def set_start_point(self):
       """Sets the start point of a test run.
 
@@ -401,8 +405,7 @@ def run(self):
     utils.create_dir(self._test_run_metadata.root_output_path)
 
     summary_writer = records.TestSummaryWriter(
-        os.path.join(self._test_run_metadata.root_output_path,
-                     records.OUTPUT_FILE_SUMMARY))
+        self._test_run_metadata.summary_file_path)
 
     # When a SIGTERM is received during the execution of a test, the Mobly test
     # immediately terminates without executing any of the finally blocks. This
@@ -439,6 +442,7 @@ def sigterm_handler(*args):
           f'Summary for test run {self._test_run_metadata.run_id}:',
           f'Total time elapsed {self._test_run_metadata.time_elapsed_sec}s',
           f'Artifacts are saved in "{self._test_run_metadata.root_output_path}"',
+          f'Test summary saved in "{self._test_run_metadata.summary_file_path}"',
           f'Test results: {self.results.summary_str()}'
       ]
       logging.info('\n'.join(summary_lines))