Run a test to create an RNTuple EDM4hep file

and add explanations in the README.

README.md

@@ -140,6 +140,14 @@ with tools that consume JSON.
 Use `edm4hep2json --help` to see the available options for selecting which parts
 of the input file should be part of the output.
 
+## Example files
+
+Example EDM4hep files can be obtained from the Continuous Integration (CI)
+workflows. From the EDM4hep github page, go to Actions -> Key4hep build, click
+one of the runs (the latest scheduled is preferred) and they will appear at the
+bottom, under Artifacts.
+
+
 ## Contributing
 
 Contributions and bug reports are welcome! See our [contributing guidelines](doc/contributing.md) if you want to contribute code to EDM4hep.

scripts/createEDM4hepFile.py

@@ -10,14 +10,16 @@
 frames = 3  # How many frames or events will be written
 vectorsize = 5  # For vector members, each vector member will have this size
 counter = count()  # next(counter) will return 0, 1, 2, ...
-# used to generate the dummy data
-output_file = "output.root"
 
 parser = argparse.ArgumentParser(description="Create a file with EDM4hep data")
 parser.add_argument(
     "--rntuple", action="store_true", help="Use a ROOT ntuple instead of EDM4hep"
 )
+parser.add_argument(
+    "--output-file", type=str, help="Output file name", default="edm4hep.root"
+)
 args = parser.parse_args()
+output_file = args.output_file
 
 if args.rntuple:
     try:
@@ -78,9 +80,7 @@
         particle.setMomentumAtEndpoint(
             edm4hep.Vector3d(next(counter), next(counter), next(counter))
         )
-        particle.setSpin(
-            edm4hep.Vector3f(next(counter), next(counter), next(counter))
-        )
+        particle.setSpin(edm4hep.Vector3f(next(counter), next(counter), next(counter)))
         particle.setColorFlow(edm4hep.Vector2i(next(counter), next(counter)))
 
     particles[0].addToDaughters(particles[1])

test/CMakeLists.txt

@@ -13,9 +13,12 @@ function(set_test_env _testname)
     )
 endfunction()
 
-add_test(NAME "Create an EDM4hep data file" COMMAND python ${PROJECT_SOURCE_DIR}/scripts/createEDM4hepFile.py)
+add_test(NAME "Create an EDM4hep data file" COMMAND python ${PROJECT_SOURCE_DIR}/scripts/createEDM4hepFile.py --output-file edm4hep_example.root)
 set_test_env("Create an EDM4hep data file")
 
+add_test(NAME "Create an EDM4hep data file (RNTuple)" COMMAND python ${PROJECT_SOURCE_DIR}/scripts/createEDM4hepFile.py --rntuple --output-file edm4hep_example_rntuple.root)
+set_test_env("Create an EDM4hep data file (RNTuple)")
+
 add_executable(write_events write_events.cc)
 target_include_directories(write_events PUBLIC ${PROJECT_SOURCE_DIR}/edm4hep )
 target_link_libraries(write_events edm4hep podio::podioRootIO)