Gerrit: Enable overriding step_test_data

Bug: v8:7419
Change-Id: I49ad9358b9487b76503c3c1f4d6838aa0dd42736
Reviewed-on: https://chromium-review.googlesource.com/938969
Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>

recipes/README.recipes.md

@@ -353,7 +353,7 @@ Args:
 Returns:
   the name of the branch
 
-— **def [get\_changes](/recipes/recipe_modules/gerrit/api.py#122)(self, host, query_params, start=None, limit=None, o_params=None, \*\*kwargs):**
+— **def [get\_changes](/recipes/recipe_modules/gerrit/api.py#122)(self, host, query_params, start=None, limit=None, o_params=None, step_test_data=None, \*\*kwargs):**
 
 Query changes for the given host.
 
@@ -366,6 +366,7 @@ Args:
   limit: Maximum number of results to return.
   o_params: A list of additional output specifiers, as documented here:
       https://gerrit-review.googlesource.com/Documentation/rest-api-changes.html#list-changes
+  step_test_data: Optional mock test data for the underlying gerrit client.
 Returns:
   A list of change dicts as documented here:
       https://gerrit-review.googlesource.com/Documentation/rest-api-changes.html#list-changes

recipes/recipe_modules/gerrit/api.py

@@ -120,7 +120,7 @@ class GerritApi(recipe_api.RecipeApi):
             host, change, patchset))
 
   def get_changes(self, host, query_params, start=None, limit=None,
-                  o_params=None, **kwargs):
+                  o_params=None, step_test_data=None, **kwargs):
     """
     Query changes for the given host.
 
@@ -133,6 +133,7 @@ class GerritApi(recipe_api.RecipeApi):
       limit: Maximum number of results to return.
       o_params: A list of additional output specifiers, as documented here:
           https://gerrit-review.googlesource.com/Documentation/rest-api-changes.html#list-changes
+      step_test_data: Optional mock test data for the underlying gerrit client.
     Returns:
       A list of change dicts as documented here:
           https://gerrit-review.googlesource.com/Documentation/rest-api-changes.html#list-changes
@@ -150,10 +151,12 @@ class GerritApi(recipe_api.RecipeApi):
       args += ['-p', '%s=%s' % (k, v)]
     for v in (o_params or []):
       args += ['-o', v]
+    if not step_test_data:
+      step_test_data = lambda: self.test_api.get_one_change_response_data()
 
     return self(
         kwargs.pop('name', 'changes'),
         args,
-        step_test_data=lambda: self.test_api.get_one_change_response_data(),
+        step_test_data=step_test_data,
         **kwargs
     ).json.output