BuildAPI: Unit test cleanup / additions

BUG=none
TEST=manual,run_tests

Change-Id: I6c2056531bd1ea0f9209264edbf9295671f31697
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/1987853
Tested-by: Michael Mortensen <mmortensen@google.com>
Reviewed-by: Alex Klein <saklein@chromium.org>
Commit-Queue: Michael Mortensen <mmortensen@google.com>
diff --git a/api/controller/packages_unittest.py b/api/controller/packages_unittest.py
index b421f8f..fc71c60 100644
--- a/api/controller/packages_unittest.py
+++ b/api/controller/packages_unittest.py
@@ -490,6 +490,16 @@
                                           self.validate_only_config)
     patch.assert_not_called()
 
+  def testMockCall(self):
+    """Test that a mock call does not execute logic, returns mocked value."""
+    patch = self.PatchObject(packages_service, 'has_prebuilt')
+
+    request = self._GetRequest(board='betty')
+    packages_controller.HasChromePrebuilt(request, self.response,
+                                          self.mock_call_config)
+    patch.assert_not_called()
+    self.assertTrue(self.response.has_prebuilt)
+
   def testNoBuildTargetFails(self):
     """No build target argument should fail."""
     request = self._GetRequest()