diff --git a/ApplicationLibCode/UnitTests/RimDeltaSummaryEnsemble-Test.cpp b/ApplicationLibCode/UnitTests/RimDeltaSummaryEnsemble-Test.cpp
index 774e1454c8..75210e6db3 100644
--- a/ApplicationLibCode/UnitTests/RimDeltaSummaryEnsemble-Test.cpp
+++ b/ApplicationLibCode/UnitTests/RimDeltaSummaryEnsemble-Test.cpp
@@ -2,8 +2,6 @@
 
 #include "Summary/RiaSummaryTools.h"
 
-#include "RigCaseRealizationParameters.h"
-
 #include "RimDeltaSummaryEnsemble.h"
 #include "RimMockSummaryCase.h"
 #include "RimSummaryCaseMainCollection.h"
@@ -15,22 +13,10 @@
 #include "cafPdmPtrField.h"
 
 #include <algorithm>
-#include <memory>
 #include <vector>
 
 namespace
 {
-RimSummaryCase* createMockCase( int realizationNumber )
-{
-    auto* summaryCase = new RimMockSummaryCase();
-
-    auto parameters = std::make_shared<RigCaseRealizationParameters>();
-    parameters->setRealizationNumber( realizationNumber );
-    summaryCase->setCaseRealizationParameters( parameters );
-
-    return summaryCase;
-}
-
 size_t countOf( const std::vector<RimDeltaSummaryEnsemble*>& ensembles, const RimDeltaSummaryEnsemble* ensemble )
 {
     return static_cast<size_t>( std::count( ensembles.begin(), ensembles.end(), ensemble ) );
diff --git a/ApplicationLibCode/UnitTests/RimMockSummaryCase.h b/ApplicationLibCode/UnitTests/RimMockSummaryCase.h
index b835f87476..6544395f7a 100644
--- a/ApplicationLibCode/UnitTests/RimMockSummaryCase.h
+++ b/ApplicationLibCode/UnitTests/RimMockSummaryCase.h
@@ -1,9 +1,11 @@
 #pragma once
 
 #include "RifSummaryReaderInterface.h"
+#include "RigCaseRealizationParameters.h"
 #include "RimSummaryCase.h"
 
 #include <map>
+#include <memory>
 #include <string>
 #include <vector>
 
@@ -63,3 +65,17 @@ private:
     QString                                        m_name = "MockCase";
     std::map<RifEclipseSummaryAddress, VectorData> m_data;
 };
+
+//--------------------------------------------------------------------------------------------------
+/// A mock case carrying the realization number a delta ensemble matches its source cases on.
+//--------------------------------------------------------------------------------------------------
+inline RimSummaryCase* createMockCase( int realizationNumber )
+{
+    auto* summaryCase = new RimMockSummaryCase();
+
+    auto parameters = std::make_shared<RigCaseRealizationParameters>();
+    parameters->setRealizationNumber( realizationNumber );
+    summaryCase->setCaseRealizationParameters( parameters );
+
+    return summaryCase;
+}
diff --git a/ApplicationLibCode/UnitTests/RimSummaryCaseMainCollection-Test.cpp b/ApplicationLibCode/UnitTests/RimSummaryCaseMainCollection-Test.cpp
index 2d0089344b..f186a17e9c 100644
--- a/ApplicationLibCode/UnitTests/RimSummaryCaseMainCollection-Test.cpp
+++ b/ApplicationLibCode/UnitTests/RimSummaryCaseMainCollection-Test.cpp
@@ -2,8 +2,6 @@
 
 #include "Summary/RiaSummaryTools.h"
 
-#include "RigCaseRealizationParameters.h"
-
 #include "RimDeltaSummaryEnsemble.h"
 #include "RimMockSummaryCase.h"
 #include "RimSummaryCaseMainCollection.h"
@@ -13,23 +11,8 @@
 #include "cafPdmPointer.h"
 
 #include <algorithm>
-#include <memory>
 #include <vector>
 
-namespace
-{
-RimSummaryCase* createMockCase( int realizationNumber )
-{
-    auto* summaryCase = new RimMockSummaryCase();
-
-    auto parameters = std::make_shared<RigCaseRealizationParameters>();
-    parameters->setRealizationNumber( realizationNumber );
-    summaryCase->setCaseRealizationParameters( parameters );
-
-    return summaryCase;
-}
-} // namespace
-
 //--------------------------------------------------------------------------------------------------
 /// Removing a source case makes a delta ensemble rebuild its derived cases. Those derived cases are
 /// part of the list of cases to remove, and must stay alive for as long as the caller holds that