depot_tools: add test_api to infra_paths recipe module

recipe_modules/infra_paths/api.py

Index: recipe_modules/infra_paths/api.py
diff --git a/recipe_modules/infra_paths/api.py b/recipe_modules/infra_paths/api.py
index c84928c4fa8f375a296da139ba5f6ca2a848c9f8..1b902826f1138bce66defc1c86bc74f91d964835 100644
--- a/recipe_modules/infra_paths/api.py
+++ b/recipe_modules/infra_paths/api.py
@@ -3,6 +3,7 @@
 # found in the LICENSE file.
 
 from recipe_engine import recipe_api
+from recipe_engine.config_types import Path, NamedBasePath
 
 
 class InfraPathsApi(recipe_api.RecipeApi):
@@ -28,6 +29,10 @@ class InfraPathsApi(recipe_api.RecipeApi):
     else:
       self.set_config('buildbot')
 
+    for path in self._test_data.get('exists', []):
+      assert isinstance(path.base, NamedBasePath)
+      self.m.path.mock_add_paths(self[path.base.name].join(*path.pieces))
+
   def __getitem__(self, name):
     self._lazy_set_config()
     return self.c.paths[name]