[TMVA] Add extra logging output to test case

Sometimes the serialised methods will fail to load due to missing files.
This adds more output and checks to verify that required files exist to
better pinpoint the problem.

tmva/tmva/test/crossvalidation/TestCrossValidationMultiProc.cxx

@@ -79,7 +79,7 @@ std::pair<std::string, double> runCrossValidation(UInt_t numWorkers)
    // TMVA::CrossValidation takes ownership of dataloader
    std::string splitExpr = "int([EventNumber])%int([NumFolds]";
    TMVA::CrossValidation cv{Form("%i-proc", numWorkers), dataloader,
-                            Form("Silent:AnalysisType=Classification"
+                            Form("!Silent:AnalysisType=Classification"
                                  ":NumWorkerProcs=%i:NumFolds=%i"
                                  ":SplitExpr=%s)",
                                  numWorkers, NUM_FOLDS, splitExpr.c_str())};
@@ -97,6 +97,7 @@ std::pair<std::string, double> runCrossValidation(UInt_t numWorkers)
    std::string dsname{dataloader->GetName()};
    std::string cvname{cv.GetName()};
    std::string weightPath = dsname + "/weights/" + cvname + "_BDT.weights.xml";
+
    return std::make_pair(weightPath, duration);
 }
 
@@ -149,5 +150,14 @@ TEST(CrossValidationMultiprocess, EqualOutputTo)
    // Verify that the two models generate the same output given the same input.
    std::string weightPath1 = std::get<0>(p1);
    std::string weightPath2 = std::get<0>(p2);
+
+   // AccessPathName() == kFALSE means file exits
+   ASSERT_FALSE(gSystem->AccessPathName(weightPath1.c_str())) << "Method was"
+      << " not serialised correctly. Path: '" << weightPath1 << "' does not"
+      << " exist.";
+   ASSERT_FALSE(gSystem->AccessPathName(weightPath2.c_str())) << "Method was"
+      << " not serialised correctly. Path: '" << weightPath2 << "' does not"
+      << " exist.";
+
    verify(weightPath1, weightPath2);
 }