Add simple depends_on API.

recipe_engine/recipe_test_api.py

Index: recipe_engine/recipe_test_api.py
diff --git a/recipe_engine/recipe_test_api.py b/recipe_engine/recipe_test_api.py
index 4a54194489b410892b3fac0c14643ea055c0d385..dcb705650d2c2ff2dd5948a8a46a959df253bfb2 100644
--- a/recipe_engine/recipe_test_api.py
+++ b/recipe_engine/recipe_test_api.py
@@ -6,6 +6,7 @@ import collections
 import contextlib
 
 from .util import ModuleInjectionSite, static_call, static_wraps
+from .types import freeze
 
 def combineify(name, dest, a, b):
   """
@@ -160,6 +161,7 @@ class TestData(BaseTestData):
     self.properties = {}  # key -> val
     self.mod_data = collections.defaultdict(ModuleTestData)
     self.step_data = collections.defaultdict(StepTestData)
+    self.depend_on_data = {}
     self.expected_exception = None
 
   def __add__(self, other):
@@ -171,6 +173,7 @@ class TestData(BaseTestData):
 
     combineify('mod_data', ret, self, other)
     combineify('step_data', ret, self, other)
+    combineify('depend_on_data', ret, self, other)
     ret.expected_exception = self.expected_exception
     if other.expected_exception:
       ret.expected_exception = other.expected_exception
@@ -230,6 +233,12 @@ class TestData(BaseTestData):
     if not should_raise:
       self.expected_exception = None
 
+  def depend_on(self, recipe, properties, result):
+    tup = freeze((recipe, properties))
+    assert tup not in self.depend_on_data, (
+        'Already gave test data for recipe %s with properties %r' % tup)
+    self.depend_on_data[tup] = freeze(result)
+
   def __repr__(self):
     return "TestData(%r)" % ({
       'name': self.name,
@@ -237,6 +246,7 @@ class TestData(BaseTestData):
       'mod_data': dict(self.mod_data.iteritems()),
       'step_data': dict(self.step_data.iteritems()),
       'expected_exception': self.expected_exception,
+      'depend_on_data': self.depend_on_data,
     },)
 
 
@@ -494,3 +504,8 @@ class RecipeTestApi(object):
     ret = TestData(None)
     ret.expect_exception(exc_type)
     return ret
+
+  def depend_on(self, recipe, properties, result):
+    ret = TestData()
+    ret.depend_on(recipe, properties, result)
+    return ret