psu-ng: Create error for communication fault

Signed-off-by: Brandon Wyman <bjwyman@gmail.com>
Change-Id: I3f147063759559bf2486e78d9873c6d464381ddd
diff --git a/phosphor-power-supply/test/mock.hpp b/phosphor-power-supply/test/mock.hpp
index 63afffe..02e3947 100644
--- a/phosphor-power-supply/test/mock.hpp
+++ b/phosphor-power-supply/test/mock.hpp
@@ -22,6 +22,7 @@
     MOCK_METHOD(void, writeBinary,
                 (const std::string& name, std::vector<uint8_t> data, Type type),
                 (override));
+    MOCK_METHOD(const fs::path&, path, (), (const, override));
 };
 } // namespace pmbus