IVGCVSW-6676 Register CopyAndImportFactoryPairs to RefBackend and unit tests

Signed-off-by: Narumol Prangnawarat <narumol.prangnawarat@arm.com>
Change-Id: I9d695418fe240b7115a1c624abcd459f1459301b
diff --git a/src/backends/reference/backend.mk b/src/backends/reference/backend.mk
index 0ddb16a..33e161c 100644
--- a/src/backends/reference/backend.mk
+++ b/src/backends/reference/backend.mk
@@ -133,6 +133,7 @@
 
 BACKEND_TEST_SOURCES := \
         test/ArgMinMaxTests.cpp \
+        test/RefBackendTests.cpp \
         test/RefCreateWorkloadTests.cpp \
         test/RefDetectionPostProcessTests.cpp \
         test/RefEndToEndTests.cpp \