diff --git a/.gitignore b/.gitignore
index 1088272d..415b87da 100644
--- a/.gitignore
+++ b/.gitignore
@@ -290,6 +290,7 @@ __pycache__/
 # Calculator specific
 Generated Files/
 src/GraphControl/GraphingImplOverrides.props
+src/CalcViewModel/DataLoaders/DataLoaderConstants.h
 !/build/config/TRexDefs/**
 !src/Calculator/TemporaryKey.pfx
 !src/CalculatorUnitTests/CalculatorUnitTests_TemporaryKey.pfx
\ No newline at end of file
diff --git a/src/CalcViewModel/CalcViewModel.vcxproj b/src/CalcViewModel/CalcViewModel.vcxproj
index 8d1f8a20..f51a5e4a 100644
--- a/src/CalcViewModel/CalcViewModel.vcxproj
+++ b/src/CalcViewModel/CalcViewModel.vcxproj
@@ -344,7 +344,6 @@
     <ClInclude Include="Common\TraceLogger.h" />
     <ClInclude Include="Common\Utils.h" />
     <ClInclude Include="Common\ValidatingConverters.h" />
-    <ClInclude Include="DataLoaders\DataLoaderConstants.h" />
     <ClInclude Include="DataLoaders\CurrencyDataLoader.h" />
     <ClInclude Include="DataLoaders\CurrencyHttpClient.h" />
     <ClInclude Include="DataLoaders\ICurrencyHttpClient.h" />
@@ -409,6 +408,17 @@
       <Project>{311e866d-8b93-4609-a691-265941fee101}</Project>
     </ProjectReference>
   </ItemGroup>
+  <ItemDefinitionGroup Condition="!Exists('DataLoaders\DataLoaderConstants.h')">
+    <ClCompile>
+      <AdditionalOptions>/DUSE_MOCK_DATA %(AdditionalOptions)</AdditionalOptions>
+    </ClCompile>
+  </ItemDefinitionGroup>
+  <ItemGroup Condition="!Exists('DataLoaders\DataLoaderConstants.h')">
+	<ClInclude Include="DataLoaders\DataLoaderMockConstants.h" />
+  </ItemGroup>
+  <ItemGroup Condition="Exists('DataLoaders\DataLoaderConstants.h')">
+	<ClInclude Include="DataLoaders\DataLoaderConstants.h" />
+  </ItemGroup>
   <ItemGroup>
     <None Include="DataLoaders\DefaultFromToCurrency.json" />
     <None Include="packages.config" />
diff --git a/src/CalcViewModel/CalcViewModel.vcxproj.filters b/src/CalcViewModel/CalcViewModel.vcxproj.filters
index 4f43baf3..bd0d75f6 100644
--- a/src/CalcViewModel/CalcViewModel.vcxproj.filters
+++ b/src/CalcViewModel/CalcViewModel.vcxproj.filters
@@ -213,6 +213,9 @@
     <ClInclude Include="Common\TraceActivity.h">
       <Filter>Common</Filter>
     </ClInclude>
+    <ClInclude Include="DataLoaders\DataLoaderMockConstants.h">
+      <Filter>DataLoaders</Filter>
+    </ClInclude>
     <ClInclude Include="DataLoaders\DataLoaderConstants.h">
       <Filter>DataLoaders</Filter>
     </ClInclude>
diff --git a/src/CalcViewModel/DataLoaders/CurrencyHttpClient.cpp b/src/CalcViewModel/DataLoaders/CurrencyHttpClient.cpp
index 9af30e01..28087037 100644
--- a/src/CalcViewModel/DataLoaders/CurrencyHttpClient.cpp
+++ b/src/CalcViewModel/DataLoaders/CurrencyHttpClient.cpp
@@ -3,7 +3,12 @@
 
 #include "pch.h"
 #include "CurrencyHttpClient.h"
+
+#ifdef USE_MOCK_DATA
+#include "DataLoaderMockConstants.h"
+#else
 #include "DataLoaderConstants.h"
+#endif
 
 using namespace CalculatorApp::DataLoaders;
 using namespace Platform;
diff --git a/src/CalcViewModel/DataLoaders/DataLoaderConstants.h b/src/CalcViewModel/DataLoaders/DataLoaderMockConstants.h
similarity index 100%
rename from src/CalcViewModel/DataLoaders/DataLoaderConstants.h
rename to src/CalcViewModel/DataLoaders/DataLoaderMockConstants.h