Add file.filesizes to recipe engine core modules.

recipe_modules/file/test_api.py

 # Copyright 2017 The LUCI Authors. All rights reserved.
 # Use of this source code is governed under the Apache License, Version 2.0
 # that can be found in the LICENSE file.
 
 import os
 
 from recipe_engine import recipe_test_api
 
 
 class FileTestApi(recipe_test_api.RecipeTestApi):
@@ skipping 10 matching lines @@
         + api.step_data('listdir step name', api.file.listdir(['a', 'b', 'c']))
     """
     def _check(name):
       name = str(name)
       if '/' in name or '\\' in name:  # pragma: no cover
         raise ValueError('file name contains slash: %r' % name)
       return name
     return (self.m.raw_io.stream_output('\n'.join(sorted(map(_check, names))))
             + self.errno(errno_name))
 
+  def filesizes(self, sizes=(), errno_name=0):
+    """Provides test mock for the `filesizes` method.
+
+    Args:
+      sizes (iterable[int]) - The list of sizes to return.
+      errno_name (str|None) - The error name for this step to return, if any.
+
+    Example:
+      yield (api.test('my_test')
+        + api.step_data('filesize step name', api.file.filesizes([1674, 5714]))
+    """
+    return (self.m.raw_io.stream_output('\n'.join(sizes))
+            + self.errno(errno_name))
+
   def read_text(self, text_content='', errno_name=0):
     """Provides test mock for the `read_text` method.
 
     Args:
       text_content (str) - The text data for this read_text step to return.
       errno_name (str|None) - The error name for this step to return, if any.
 
     Example:
       yield (api.test('my_test')
         + api.step_data('read step name',
@@ skipping 28 matching lines @@
         This must be e.g. 'EPERM', 'EEXIST', etc.
     """
     data = {'ok': True}
     if errno_name:
       data['ok'] = False
       data['errno_name'] = errno_name
       # in real operation, this message will come from the underlying OS and
       # will potentially have descriptive detail.
       data['message'] = 'file command encountered system error '+errno_name
     return self.m.json.output(data)