[RF] Test schema evolution of RooDataHist from version 5 and 6

Extend the RooDataHist tests to also validate the schema evolution
from version 5 and version 6.

Version 6 is the current version, so the `dataHistv6_ref.root` reference
file was produced with ROOT master. Version 5 was used in ROOT 6.24,
which was used to produce the `dataHistv5_ref.root` reference file.

Author: guitargeek

roofit/roofitcore/test/CMakeLists.txt

@@ -10,7 +10,9 @@ ROOT_ADD_GTEST(simple simple.cxx LIBRARIES RooFitCore)
 ROOT_ADD_GTEST(testWorkspace testWorkspace.cxx LIBRARIES RooFitCore RooFit RooStats)
 if(NOT MSVC OR win_broken_tests)
   ROOT_ADD_GTEST(testRooDataHist testRooDataHist.cxx LIBRARIES RooFitCore
-    COPY_TO_BUILDDIR ${CMAKE_CURRENT_SOURCE_DIR}/dataHistv4_ref.root)
+    COPY_TO_BUILDDIR ${CMAKE_CURRENT_SOURCE_DIR}/dataHistv4_ref.root
+                     ${CMAKE_CURRENT_SOURCE_DIR}/dataHistv5_ref.root
+                     ${CMAKE_CURRENT_SOURCE_DIR}/dataHistv6_ref.root)
 endif()
 ROOT_ADD_GTEST(testRooSimPdfBuilder testRooSimPdfBuilder.cxx LIBRARIES RooFitCore RooFit)
 ROOT_ADD_GTEST(testRooWrapperPdf testRooWrapperPdf.cxx LIBRARIES Gpad RooFitCore)

roofit/roofitcore/test/dataHistv5_ref.root

@@ -180,14 +180,25 @@ TEST(RooDataHist, WeightedEntries)
   EXPECT_EQ(weight, weightBin10);
 }
 
-TEST(RooDataHist, ReadV4Legacy)
-{
-  TFile v4Ref("dataHistv4_ref.root");
-  ASSERT_TRUE(v4Ref.IsOpen());
+class RooDataHistIO : public testing::TestWithParam<const char*> {
+public:
+  void SetUp() override {
+    TFile file(GetParam(), "READ");
+    ASSERT_TRUE(file.IsOpen());
+
+    file.GetObject("dataHist", legacy);
+    ASSERT_NE(legacy, nullptr);
+  }
+
+  void TearDown() override {
+    delete legacy;
+  }
 
-  RooDataHist* legacy = nullptr;
-  v4Ref.GetObject("dataHist", legacy);
-  ASSERT_NE(legacy, nullptr);
+protected:
+  RooDataHist* legacy{nullptr};
+};
+
+TEST_P(RooDataHistIO, ReadLegacy) {
 
   RooDataHist& dataHist = *legacy;
 
@@ -239,6 +250,10 @@ TEST(RooDataHist, ReadV4Legacy)
 }
 
 
+INSTANTIATE_TEST_SUITE_P(IO_SchemaEvol, RooDataHistIO,
+    testing::Values("dataHistv4_ref.root", "dataHistv5_ref.root", "dataHistv6_ref.root"));
+
+
 void fillHist(TH2D* histo, double content) {
   for (int i=0; i < histo->GetNbinsX()+2; ++i) {
     for (int j=0; j < histo->GetNbinsY()+2; ++j) {