[Coverage] Add sancov_formatter unittest for split.

tools/sanitizers/sancov_formatter.py

 #!/usr/bin/env python
 # Copyright 2016 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Script to transform and merge sancov files into human readable json-format.
 
 The script supports three actions:
 all: Writes a json file with all instrumented lines of all executables.
 merge: Merges sancov files with coverage output into an existing json file.
@@ skipping 383 matching lines @@
       # Flat-copy the old dict.
       new_data = dict(data)
 
       # Update current file.
       new_data['files'] = {file_name: coverage}
 
       # Write json data.
       json.dump(new_data, f, sort_keys=True)
 
 
-def main():
+def main(args=None):
   parser = argparse.ArgumentParser()
   parser.add_argument('--coverage-dir',
                       help='Path to the sancov output files.')
   parser.add_argument('--json-input',
                       help='Path to an existing json file with coverage data.')
   parser.add_argument('--json-output',
                       help='Path to a file to write json output to.')
   parser.add_argument('--output-dir',
                       help='Directory where to put split output files to.')
   parser.add_argument('action', choices=['all', 'merge', 'split'],
                       help='Action to perform.')
 
-  options = parser.parse_args()
+  options = parser.parse_args(args)
   if options.action.lower() == 'all':
     if not options.json_output:
       print '--json-output is required'
       return 1
     write_instrumented(options)
   elif options.action.lower() == 'merge':
     if not options.coverage_dir:
       print '--coverage-dir is required'
       return 1
     if not options.json_input:
       print '--json-input is required'
       return 1
     if not options.json_output:
       print '--json-output is required'
       return 1
     merge(options)
   elif options.action.lower() == 'split':
     if not options.json_input:
       print '--json-input is required'
       return 1
     if not options.output_dir:
       print '--output-dir is required'
       return 1
     split(options)
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(main())