VOL-2776 unit test for StartOmciTestAction

Change-Id: Ib0b560b2ae37fab428b3fc058f282b941c5e237f
diff --git a/rw_core/mocks/adapter_onu.go b/rw_core/mocks/adapter_onu.go
index 92dff06..549e016 100644
--- a/rw_core/mocks/adapter_onu.go
+++ b/rw_core/mocks/adapter_onu.go
@@ -219,6 +219,12 @@
 	return nil
 }
 
+// Start_omci_test begins an omci self-test
+func (onuA *ONUAdapter) Start_omci_test(device *voltha.Device, request *voltha.OmciTestRequest) (*ic.TestResponse, error) { // nolint
+	_ = device
+	return &ic.TestResponse{Result: ic.TestResponse_SUCCESS}, nil
+}
+
 // GetFlowCount returns the total number of flows presently under this adapter
 func (onuA *ONUAdapter) GetFlowCount() int {
 	onuA.lock.Lock()