Refactor the way that TestApi works so that it is actually useful.

scripts/slave/recipe_modules/raw_io/api.py

+from slave import recipe_api
+from slave import recipe_util
+
+import os
+import tempfile
+
+class InputDataPlaceholder(recipe_util.Placeholder):
+  def __init__(self, data, suffix):
+    assert isinstance(data, basestring)
+    self.data = data
+    self.suffix = suffix
+    self.input_file = None
+    super(InputDataPlaceholder, self).__init__()
+
+  def render(self, test):
+    if test.enabled:
+      # cheat and pretend like we're going to pass the data on the
+      # cmdline for test expectation purposes.
+      return [self.data]
+    else:  # pragma: no cover
+      input_fd, self.input_file = tempfile.mkstemp(suffix=self.suffix)
+      os.write(input_fd, self.data)
+      os.close(input_fd)
+      return [self.input_file]
+
+  def result(self, presentation, test):
+    if not test.enabled:  # pragma: no cover
+      os.unlink(self.input_file)
+
+
+class OutputDataPlaceholder(recipe_util.Placeholder):
+  def __init__(self, suffix):
+    self.suffix = suffix
+    self.output_file = None
+    super(OutputDataPlaceholder, self).__init__()
+
+  def render(self, test):
+    if test.enabled:
+      return ['/path/to/tmp/' + self.suffix.lstrip('.')]
+    else:  # pragma: no cover
+      output_fd, self.output_file = tempfile.mkstemp(self.suffix)
+      os.close(output_fd)
+      return [self.output_file]
+
+  def result(self, presentation, test):
+    if test.enabled:
+      return test.data
+    else:  # pragma: no cover
+      assert self.output_file is not None
+      try:
+        with open(self.output_file.read(), 'rb') as f:
+          return f.read()
+      finally:
+        os.unlink(self.output_file)
+
+
+class RawIOApi(recipe_api.RecipeApi):
+  @recipe_util.returns_placeholder
+  @staticmethod
+  def input(data, suffix):
+    return InputDataPlaceholder(data, suffix)
+
+  @recipe_util.returns_placeholder
+  @staticmethod
+  def output(suffix):
+    return OutputDataPlaceholder(suffix)