From 7bab764b2e06f14c4a0e04282684e58e05e055df Mon Sep 17 00:00:00 2001
From: Vincenzo Eduardo Padulano <vincenzo.eduardo.padulano@cern.ch>
Date: Wed, 5 Aug 2026 11:31:06 +0200
Subject: [PATCH] [io] Add gtest-based cpp11Containers unordered_map test

This is a re-write of the cpp11Containers-unorderedMap test as a compiled C++
program based on gtest. Given the recent intermittent CI failures, the new test
could help identify in a more fine-grained way the root cause. It is an addition
rather than a substitution because there is no guarantee that the cause of the
CI failure is in the test itself.
---
 .../root/io/cpp11Containers/CMakeLists.txt    |  13 +
 .../cpp11Containers/unorderedMapUnitTests.cxx | 365 ++++++++++++++++++
 2 files changed, 378 insertions(+)
 create mode 100644 roottest/root/io/cpp11Containers/unorderedMapUnitTests.cxx

diff --git a/roottest/root/io/cpp11Containers/CMakeLists.txt b/roottest/root/io/cpp11Containers/CMakeLists.txt
index 086779fa44b5a..d3bf41d3c0713 100644
--- a/roottest/root/io/cpp11Containers/CMakeLists.txt
+++ b/roottest/root/io/cpp11Containers/CMakeLists.txt
@@ -10,6 +10,19 @@ ROOTTEST_ADD_TEST(unorderedMap
                   FIXTURES_SETUP root-io-cpp11Containers-unorderedMap-fixture
                   LABELS longtest)
 
+# Copy of the test above, written as a compiled C++ program based on gtest. Useful for more fine-grained view on
+# potential test failures
+ROOTTEST_GENERATE_EXECUTABLE(
+    unorderedMapUnitTests
+    unorderedMapUnitTests.cxx
+    LIBRARIES Core RIO Tree TreePlayer Hist GTest::gtest GTest::gtest_main GTest::gmock GTest::gmock_main ROOT::TestSupport
+    FIXTURES_REQUIRED root-io-cpp11Containers-unorderedMapDict-fixture
+    FIXTURES_SETUP root-io-cpp11Containers-unorderedMapUnitTests-fixture)
+
+ROOTTEST_ADD_TEST(unorderedMapUnitTests
+    EXEC ${CMAKE_CURRENT_BINARY_DIR}/unorderedMapUnitTests
+    FIXTURES_REQUIRED root-io-cpp11Containers-unorderedMapUnitTests-fixture)
+
 if(NOT 32BIT AND NOT MSVC)
    ROOTTEST_GENERATE_REFLEX_DICTIONARY(forwardList
                                        forwardList.h
diff --git a/roottest/root/io/cpp11Containers/unorderedMapUnitTests.cxx b/roottest/root/io/cpp11Containers/unorderedMapUnitTests.cxx
new file mode 100644
index 0000000000000..714f15c7a789f
--- /dev/null
+++ b/roottest/root/io/cpp11Containers/unorderedMapUnitTests.cxx
@@ -0,0 +1,365 @@
+// Test the usage of different instantiations of std::map, std::multimap, std::unordered_map, std::unordered_multimap
+// Each container has a dictionary generated via an XML selection file
+// We test storage of each container as:
+// * A whole object written directly to a TFile
+// * An unsplit branch in a TTree
+// * A split branch in a TTree
+
+#include <gtest/gtest.h>
+
+#include <map>
+#include <random>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+#include <ROOT/TestSupport.hxx>
+#include <RtypesCore.h>
+#include <TFile.h>
+#include <TTree.h>
+#include <TTreeReader.h>
+#include <TH1F.h>
+#include <TROOT.h>
+
+// Test fixture based on different container types and key types
+
+// Wrapper type used to instantiate pairs of concrete types to use in the
+// TYPED_TEST_SUITE macro call
+template <template <typename...> typename MapType>
+struct MapWrapper {
+   template <typename Key, typename Value>
+   using wrapped_type = MapType<Key, Value>;
+};
+
+template <typename T>
+struct cpp11ContainersUnorderedMap : public testing::Test {
+
+   // Type of the key of the container type being tested
+   using KeyType = typename T::first_type;
+
+   // Container type being tested, not fully instantiated yet but used
+   // to create different data members with the concretely instantiated type
+   template <typename K, typename V>
+   using ContType = typename T::second_type::template wrapped_type<K, V>;
+
+   static inline bool fAddDirectoryStatus{};
+   static inline unsigned fNEvents{100};
+
+   ContType<KeyType, double> fDoubleCont{{1, 1.}, {2, 2.}, {3, 3.}, {4, 4.}};
+   ContType<KeyType, TH1F> fHistoCont{{1, TH1F("h1", "ht", 100, -2, 2)}, {9, TH1F("h2", "ht", 10, -1.2, 1.2)}};
+
+   std::vector<ContType<KeyType, TH1F>> fVecHistoCont{
+      {{1, TH1F("h1", "ht", 100, -2, 2)}, {2, TH1F("h2", "ht", 10, -1.23, 1.23)}},
+      {{7, TH1F("h3", "ht", 100, -23, 23)}, {8, TH1F("h4", "ht", 10, -1.92, 1.92)}}};
+
+   ContType<KeyType, std::vector<TH1F>> fContHistoVec{
+      {1, {TH1F("h1", "ht", 100, -2, 2), TH1F("h2", "ht", 10, -1.23, 1.23)}},
+      {2, {TH1F("h3", "ht", 100, -23, 23), TH1F("h4", "ht", 10, -1.92, 1.92)}}};
+
+   std::mt19937 fRNG{1};
+   std::normal_distribution<double> fGaus{0., 1.};
+   std::uniform_real_distribution<double> fUniform{1., 2.};
+
+   static void SetUpTestSuite()
+   {
+      fAddDirectoryStatus = ROOT::Experimental::ObjectAutoRegistrationEnabled();
+      TH1::AddDirectory(false);
+   }
+
+   static void TearDownTestSuite() { TH1::AddDirectory(fAddDirectoryStatus); }
+};
+
+using TestTypes = ::testing::Types<
+   // int
+   std::pair<int, MapWrapper<std::map>>, std::pair<int, MapWrapper<std::unordered_map>>,
+   std::pair<int, MapWrapper<std::multimap>>, std::pair<int, MapWrapper<std::unordered_multimap>>,
+   // float
+   std::pair<float, MapWrapper<std::map>>, std::pair<float, MapWrapper<std::unordered_map>>,
+   std::pair<float, MapWrapper<std::multimap>>, std::pair<float, MapWrapper<std::unordered_multimap>>,
+   // double
+   std::pair<double, MapWrapper<std::map>>, std::pair<double, MapWrapper<std::unordered_map>>,
+   std::pair<double, MapWrapper<std::multimap>>, std::pair<double, MapWrapper<std::unordered_multimap>>,
+   // Long64_t
+   std::pair<Long64_t, MapWrapper<std::map>>, std::pair<Long64_t, MapWrapper<std::unordered_map>>,
+   std::pair<Long64_t, MapWrapper<std::multimap>>, std::pair<Long64_t, MapWrapper<std::unordered_multimap>>>;
+TYPED_TEST_SUITE(cpp11ContainersUnorderedMap, TestTypes);
+
+// Helper functions for equality comparisons
+
+template <typename T>
+void check_eq(const T &a, const T &b)
+{
+   EXPECT_EQ(a, b);
+}
+
+template <>
+void check_eq<>(const TH1F &a, const TH1F &b)
+{
+   EXPECT_STREQ(a.GetName(), b.GetName());
+   EXPECT_STREQ(a.GetTitle(), b.GetTitle());
+
+   EXPECT_EQ(a.GetNbinsX(), b.GetNbinsX());
+   for (int i = 0; i < a.GetNbinsX(); ++i) {
+      EXPECT_EQ(a.GetBinContent(i), b.GetBinContent(i));
+
+      EXPECT_DOUBLE_EQ(a.GetBinError(i), b.GetBinError(i));
+   }
+}
+
+// We want to match associative containers of the `key:value` type. The variadic
+// template parameter list is used to help all compilers match this overload
+template <typename KeyType, typename ValueType, template <typename... Args> typename Cont, typename... Args>
+void check_eq(const Cont<KeyType, ValueType, Args...> &a, const Cont<KeyType, ValueType, Args...> &b)
+{
+   EXPECT_EQ(a.size(), b.size());
+   for (const auto &kv : a) {
+      const auto it = b.find(kv.first);
+      EXPECT_NE(it, b.cend());
+      check_eq(kv.second, it->second);
+   }
+}
+
+template <typename T>
+void check_eq(const std::vector<T> &a, const std::vector<T> &b)
+{
+   EXPECT_EQ(a.size(), b.size());
+   for (decltype(a.size()) i{}; i < a.size(); i++)
+      check_eq(a[i], b[i]);
+}
+
+// Helper functions to fill values in test fixture data members
+
+template <class Cont>
+void randomizeAssoCont(Cont &cont, std::uniform_real_distribution<double> &uniform, std::mt19937 &rng)
+{
+   // Copy value pairs into temporary vector
+   using contPair_t = std::pair<typename Cont::key_type, typename Cont::mapped_type>;
+   std::vector<contPair_t> contValues;
+   contValues.reserve(cont.size());
+   for (const auto &el : cont)
+      contValues.push_back(el);
+
+   // Note: sorting is fundamental as we want to deal with values in the same order whether
+   // they are coming from an ordered or unordered container
+   auto sortingFunction = [](const contPair_t &p1, const contPair_t &p2) { return p1.first < p2.first; };
+   std::sort(contValues.begin(), contValues.end(), sortingFunction);
+
+   cont.clear();
+   for (auto &kv : contValues) {
+      cont.insert(std::make_pair(kv.first, kv.second * uniform(rng)));
+   }
+}
+
+template <typename Cont>
+void fillHistoAssoCont(Cont &cont, std::normal_distribution<double> &gaus, std::mt19937 &rng, unsigned int n = 5000)
+{
+
+   // Copy value pairs into temporary vector
+   using contPair_t = std::pair<typename Cont::key_type, typename Cont::mapped_type>;
+   std::vector<contPair_t> contValues;
+   contValues.reserve(cont.size());
+   for (const auto &el : cont)
+      contValues.push_back(el);
+
+   // Note: sorting is fundamental as we want to deal with values in the same order whether
+   // they are coming from an ordered or unordered container
+   auto sortingFunction = [](const contPair_t &p1, const contPair_t &p2) { return p1.first < p2.first; };
+   std::sort(contValues.begin(), contValues.end(), sortingFunction);
+
+   cont.clear();
+   for (auto &kv : contValues) {
+      for (decltype(n) i{}; i < n; i++)
+         kv.second.Fill(gaus(rng));
+      cont.insert(kv);
+   }
+}
+
+template <class NestedCont>
+void fillHistoNestedAssoCont(std::vector<NestedCont> &cont, std::normal_distribution<double> &gaus, std::mt19937 &rng,
+                             unsigned int n = 5000)
+{
+   for (auto &hCont : cont) {
+      fillHistoAssoCont(hCont, gaus, rng, n);
+   }
+}
+
+void fillHistoCont(std::vector<TH1F> &cont, std::normal_distribution<double> &gaus, std::mt19937 &rng,
+                   unsigned int n = 5000)
+{
+   for (auto &h : cont)
+      for (decltype(n) i{}; i < n; i++)
+         h.Fill(gaus(rng));
+}
+
+template <class NestedCont>
+void fillHistoNestedAssoCont(NestedCont &cont, std::normal_distribution<double> &gaus, std::mt19937 &rng,
+                             unsigned int n = 5000)
+{
+   // Copy value pairs into temporary vector
+   using contPair_t = std::pair<typename NestedCont::key_type, typename NestedCont::mapped_type>;
+   std::vector<contPair_t> contValues;
+   contValues.reserve(cont.size());
+   for (const auto &el : cont)
+      contValues.push_back(el);
+
+   // Note: sorting is fundamental as we want to deal with values in the same order whether
+   // they are coming from an ordered or unordered container
+   auto sortingFunction = [](const contPair_t &p1, const contPair_t &p2) { return p1.first < p2.first; };
+   std::sort(contValues.begin(), contValues.end(), sortingFunction);
+
+   cont.clear();
+   for (auto &kv : contValues) {
+      fillHistoCont(kv.second, gaus, rng, n);
+      cont.insert(kv);
+   }
+}
+
+template <typename T>
+void fillObj(T &obj, [[maybe_unused]] std::normal_distribution<double> &gaus,
+             [[maybe_unused]] std::uniform_real_distribution<double> &uniform, [[maybe_unused]] std::mt19937 &rng)
+{
+   if constexpr (std::is_same_v<typename T::mapped_type, double>)
+      randomizeAssoCont(obj, uniform, rng);
+   else if constexpr (std::is_same_v<typename T::mapped_type, TH1F>)
+      fillHistoAssoCont(obj, gaus, rng);
+   else if constexpr (std::is_same_v<typename T::mapped_type, std::vector<TH1F>>)
+      fillHistoNestedAssoCont(obj, gaus, rng);
+   else
+      throw std::runtime_error("Unrecognized type");
+}
+
+template <typename T>
+void fillObj(std::vector<T> &obj, std::normal_distribution<double> &gaus,
+             [[maybe_unused]] std::uniform_real_distribution<double> &uniform, std::mt19937 &rng)
+{
+   fillHistoNestedAssoCont(obj, gaus, rng);
+}
+
+// Tests writing objects directly to a TFile
+
+template <typename T>
+void checkObjectWritingDirectToTFile(const T &obj, std::string_view name, std::normal_distribution<double> &gaus,
+                                     std::uniform_real_distribution<double> &uniform, std::mt19937 &rng)
+{
+   const char *filename{"cpp11ContainersUnorderedMap_DirectToTFile.root"};
+
+   rng.seed(1);
+   gaus.reset();
+   uniform.reset();
+   auto copy = obj;
+   fillObj(copy, gaus, uniform, rng);
+
+   // Write objects as a whole object directly to a TFile
+   {
+      auto f = std::make_unique<TFile>(filename, "RECREATE");
+      f->WriteObject(&copy, name.data());
+   }
+
+   // Read back the object from file and check contents
+   {
+      auto f = std::make_unique<TFile>(filename);
+      auto *objFromFile = f->Get<T>(name.data());
+      EXPECT_NE(objFromFile, nullptr) << "Error in reading object " << name << " from file " << filename << "\n";
+
+      check_eq(*objFromFile, copy);
+   }
+}
+
+TYPED_TEST(cpp11ContainersUnorderedMap, DirectToTFileDoubleCont)
+{
+   checkObjectWritingDirectToTFile(this->fDoubleCont, "fDoubleCont", this->fGaus, this->fUniform, this->fRNG);
+}
+
+TYPED_TEST(cpp11ContainersUnorderedMap, DirectToTFileHistoCont)
+{
+   checkObjectWritingDirectToTFile(this->fHistoCont, "fHistoCont", this->fGaus, this->fUniform, this->fRNG);
+}
+
+TYPED_TEST(cpp11ContainersUnorderedMap, DirectToTFileVecHistoCont)
+{
+   checkObjectWritingDirectToTFile(this->fVecHistoCont, "fVecHistoCont", this->fGaus, this->fUniform, this->fRNG);
+}
+
+TYPED_TEST(cpp11ContainersUnorderedMap, DirectToTFileContHistoVec)
+{
+   checkObjectWritingDirectToTFile(this->fContHistoVec, "fContHistoVec", this->fGaus, this->fUniform, this->fRNG);
+}
+
+// Tests writing objects to TTree branches, in both split and unsplit mode
+
+template <typename T>
+void checkObjectWritingToTBranch(const T &obj, std::string_view name, unsigned nEvents,
+                                 std::normal_distribution<double> &gaus,
+                                 std::uniform_real_distribution<double> &uniform, std::mt19937 &rng)
+{
+   std::string filename{"cpp11ContainersUnorderedMap_ToTBranch.root"};
+   std::string splitName = std::string{name} + "_split";
+   std::string unsplitName = std::string{name} + "_unsplit";
+   auto copyForWrite = obj;
+   auto copyForRead = obj;
+
+   // Write
+   rng.seed(1);
+   gaus.reset();
+   uniform.reset();
+   {
+      auto f = std::make_unique<TFile>(filename.c_str(), "UPDATE");
+      auto t = std::make_unique<TTree>("t", "Test Tree");
+      t->Branch(splitName.c_str(), &copyForWrite, 16000, 99);
+      t->Branch(unsplitName.c_str(), &copyForWrite, 16000, 0);
+
+      for (unsigned i = 0; i < nEvents; ++i) {
+         fillObj(copyForWrite, gaus, uniform, rng);
+         t->Fill();
+      }
+
+      f->Write();
+   }
+
+   // Read
+   rng.seed(1);
+   gaus.reset();
+   uniform.reset();
+   {
+      auto f = std::make_unique<TFile>(filename.c_str());
+      std::unique_ptr<TTree> t{f->Get<TTree>("t")};
+      TTreeReader r{t.get()};
+      TTreeReaderValue<T> splitRV{r, splitName.c_str()};
+      TTreeReaderValue<T> unsplitRV{r, unsplitName.c_str()};
+      for (unsigned i = 0; i < nEvents; ++i) {
+         EXPECT_TRUE(r.Next());
+         fillObj(copyForRead, gaus, uniform, rng);
+         check_eq(*splitRV, copyForRead);
+         check_eq(*unsplitRV, copyForRead);
+      }
+   }
+}
+
+TYPED_TEST(cpp11ContainersUnorderedMap, ToTBranchDoubleCont)
+{
+   checkObjectWritingToTBranch(this->fDoubleCont, "fDoubleCont", this->fNEvents, this->fGaus, this->fUniform,
+                               this->fRNG);
+}
+
+TYPED_TEST(cpp11ContainersUnorderedMap, ToTBranchHistoCont)
+{
+   checkObjectWritingToTBranch(this->fHistoCont, "fHistoCont", this->fNEvents, this->fGaus, this->fUniform, this->fRNG);
+}
+
+TYPED_TEST(cpp11ContainersUnorderedMap, ToTBranchVecHistoCont)
+{
+   checkObjectWritingToTBranch(this->fVecHistoCont, "fVecHistoCont", this->fNEvents, this->fGaus, this->fUniform,
+                               this->fRNG);
+}
+
+TYPED_TEST(cpp11ContainersUnorderedMap, ToTBranchContHistoVec)
+{
+   checkObjectWritingToTBranch(this->fContHistoVec, "fContHistoVec", this->fNEvents, this->fGaus, this->fUniform,
+                               this->fRNG);
+}
+
+int main(int argc, char **argv)
+{
+   ::testing::InitGoogleTest(&argc, argv);
+   return RUN_ALL_TESTS();
+}