Develop a test that works on root flat files

[gordonwatts]

This issue is currently a place to collect information building towards this goal. First - we need stable datasets on the GRID - ATLAS' PHYSLITE is perfect for this:

[lxplus717] rucio list-files data15_13TeV:data15_13TeV.00282784.physics_Main.deriv.DAOD_PHYSLITE.r9264_p3083_p4165_tid21568807_00
+---------------------------------------------------------+--------------------------------------+-------------+------------+----------+
| SCOPE:NAME                                              | GUID                                 | ADLER32     | FILESIZE   |   EVENTS |
|---------------------------------------------------------+--------------------------------------+-------------+------------+----------|
| data15_13TeV:DAOD_PHYSLITE.21568807._000001.pool.root.1 | BBE3DF34-D389-4F47-9EC6-9E96F56E335C | ad:9971d948 | 557.093 MB |   142626 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000002.pool.root.1 | 8AA9E310-5428-AE4D-8C9D-349CDB2CADEC | ad:1ba4b953 | 517.352 MB |   133686 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000004.pool.root.1 | B4E12FBB-CD22-8E4F-8C21-E263BE89F403 | ad:7c5104be | 572.417 MB |   150001 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000005.pool.root.1 | 078A6168-D5ED-CA4B-87BF-A2148CF1FD18 | ad:0d0c68cc | 467.398 MB |   105451 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000006.pool.root.1 | 99BFEAA5-3457-6C4B-8C9F-FD6BE07B87E3 | ad:05d0e1dd | 526.038 MB |   125409 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000007.pool.root.1 | 1C07645E-9F81-DE40-88E8-37C1A26B77BD | ad:8219a6d2 | 498.384 MB |   118231 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000008.pool.root.1 | 6EFD2EBC-A385-2444-BC81-090772665931 | ad:17ba06a5 | 468.952 MB |   115714 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000009.pool.root.1 | 5AA426F1-6582-6547-9EBE-946CE8245DF7 | ad:82b76fb1 | 517.797 MB |   120320 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000055.pool.root.1 | D32A1044-F9EC-DF4E-9290-9FC427BA22BE | ad:c9cb3ef0 | 303.449 MB |    77325 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000057.pool.root.1 | 0FC049D9-6153-BD46-8634-82043CB900A1 | ad:0db14c7e | 262.574 MB |    67375 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000058.pool.root.1 | 0F25AE68-3183-0348-A8E4-378ADD3CFDB0 | ad:86fbc5af | 234.431 MB |    60001 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000059.pool.root.1 | 1BA312F8-76C1-D245-A11E-E95A3E42823C | ad:dd613b67 | 303.087 MB |    78441 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000060.pool.root.1 | A29AB837-1A26-CF46-9B8E-575C469A7B8D | ad:35b4a29a | 221.826 MB |    57606 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000061.pool.root.1 | CFFA1874-FE5D-9E40-BF6D-952766DAA298 | ad:4d27ac8f | 266.018 MB |    67438 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000062.pool.root.1 | 624C5E37-AF73-924B-A2F4-FBC50BD81DCD | ad:024b25cc | 299.960 MB |    78471 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000063.pool.root.1 | 0DA73CD8-F601-1D42-BF6B-0D1AFFE705EB | ad:9f8e7ddf | 294.822 MB |    77637 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000064.pool.root.1 | FEB4FDF2-989B-8946-8467-6589E3A7B7BB | ad:fd494ec9 | 287.823 MB |    76599 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000065.pool.root.1 | 695A8F65-77E3-DB4B-9B05-B5522B73A61B | ad:2556041d | 252.264 MB |    66871 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000066.pool.root.1 | 862A60A9-B22A-A844-80CF-C157CCA92BFE | ad:b2183b5d | 270.416 MB |    71927 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000071.pool.root.1 | 4BFB5635-7233-4043-A05B-1B77A1CFAA22 | ad:b7778935 | 257.650 MB |    57702 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000072.pool.root.1 | AD8B23E3-0692-6947-8F67-F67628A01FA6 | ad:1dcdce85 | 322.083 MB |    79445 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000073.pool.root.1 | 96BEC20B-A3B0-654E-86D6-2ADD71184573 | ad:14b4584f | 273.056 MB |    60567 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000074.pool.root.1 | C799CFF4-D0EB-0447-98F2-CCB8FEB7DEF0 | ad:627c379e | 344.067 MB |    76335 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000075.pool.root.1 | F6CD98E8-1F9D-5B4A-BB85-CE78BEFA19C2 | ad:ee08087a | 347.427 MB |    77967 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000077.pool.root.1 | 532858D1-DAC9-D343-B76A-00C3926EF7B7 | ad:c95d5ce1 | 318.971 MB |    72278 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000078.pool.root.1 | 834A48A3-6D55-8F43-8335-29D87008248D | ad:2a09dd00 | 351.577 MB |    78560 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000080.pool.root.1 | 50738A22-DBAF-334D-A939-E0A5AB07B81B | ad:2e8c2122 | 259.428 MB |    61639 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000081.pool.root.1 | 7B23F7E5-23C5-7442-82F1-85753FCE0AFF | ad:d26c80bc | 230.871 MB |    60856 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000082.pool.root.1 | CE918DE3-9521-ED4A-8A6D-478E3F35EE40 | ad:a771e54a | 241.077 MB |    53103 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000083.pool.root.1 | 1051A947-19EC-2C4F-B418-9EC482A397D0 | ad:2c576942 | 249.865 MB |    59731 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000084.pool.root.1 | E9ED77EA-03EF-3642-990B-D60988984B0E | ad:5b26e595 | 230.261 MB |    54455 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000085.pool.root.1 | 2AB15A95-CE2C-DD4E-B4F6-0F028F774D7A | ad:0ad9d34e | 239.562 MB |    57829 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000086.pool.root.1 | 10AD3E80-F1D6-E845-90A6-32D470AC37EF | ad:951f9ac3 | 212.687 MB |    48469 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000087.pool.root.1 | 32F26965-6DF6-9241-A7ED-9550A67399A0 | ad:a0b6c20b | 234.448 MB |    59395 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000088.pool.root.1 | E5870668-94C1-2A47-9E8E-F09F391C04EE | ad:7d3da920 | 273.905 MB |    61602 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000089.pool.root.1 | E32CA543-42F0-D848-AA6D-CC2B5DEE4391 | ad:6b56379f | 269.836 MB |    60393 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000090.pool.root.1 | 91433532-54F5-8A46-A615-C9ACEBA5C257 | ad:a79717e4 | 258.705 MB |    61105 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000091.pool.root.1 | 28F09AC8-EA3B-0441-87A4-11E880875F56 | ad:23c7078e | 208.225 MB |    48372 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000092.pool.root.1 | 5AE0EE58-026A-F648-9F90-A6965A373515 | ad:345865e3 | 252.421 MB |    60942 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000093.pool.root.1 | 0AD7D5D3-4656-714F-B87F-2501F7C4E2F4 | ad:812bdb5c | 265.728 MB |    59182 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000094.pool.root.1 | 72490D0E-5E31-314C-8490-E7C02F2C563C | ad:1220cf22 | 274.130 MB |    61142 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000095.pool.root.1 | 9B41AA68-0A67-AE48-ABD6-FB53D12E8A67 | ad:b038ae7a | 273.561 MB |    61787 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000096.pool.root.1 | A71DEDC6-98B9-7043-A278-41B759E25D42 | ad:58010f65 | 229.277 MB |    54759 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000097.pool.root.1 | C9879EBC-43B4-3C41-B0DA-02E9014EE89D | ad:1fc234e8 | 266.991 MB |    61266 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000098.pool.root.1 | D1A9C1EE-B20B-DB4A-97D8-5976EDF1258B | ad:26942e43 | 257.711 MB |    60205 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000099.pool.root.1 | C8785ED7-52BC-B84B-A6F4-486407D4FF8E | ad:b7a6464f | 249.818 MB |    56833 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000100.pool.root.1 | 4EFBD894-915C-AA45-B982-276C6BE8C38B | ad:eb0e056f | 237.323 MB |    52909 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000101.pool.root.1 | 22369DDB-CC2B-6545-A0BC-5C1116C64067 | ad:816e0470 | 240.700 MB |    54927 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000102.pool.root.1 | A982DB58-D6AD-324E-83DC-5C2720955898 | ad:08e9c5aa | 154.085 MB |    38164 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000103.pool.root.1 | 49011A4D-C355-9646-A294-949350CD343C | ad:2602a715 | 216.667 MB |    55700 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000104.pool.root.1 | 7157E5F9-F1AC-8F4E-BE37-E45E169A3A3C | ad:6463ecdd | 227.127 MB |    59495 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000105.pool.root.1 | D54859E9-511D-4247-9691-CE630D25A6BD | ad:2573f817 | 253.363 MB |    66581 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000106.pool.root.1 | 43254D06-4299-294A-9454-1ED1C9F99875 | ad:ed9129dc | 288.379 MB |    64840 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000107.pool.root.1 | 1391638E-7C50-B544-814B-0DB24D8CE22C | ad:42d555aa | 228.393 MB |    50360 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000108.pool.root.1 | E5134B3B-4D68-6646-AA06-14CD5D03AC60 | ad:94ef7514 | 225.647 MB |    54243 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000109.pool.root.1 | 8E8B5704-36B5-5746-91D5-8A76EA862D6D | ad:454bad17 | 250.638 MB |    66187 |
| data15_13TeV:DAOD_PHYSLITE.21568807._000110.pool.root.1 | 9E5A8CF8-922D-A140-841B-406925C387C1 | ad:eed3f8a2 | 110.452 MB |    26186 |
+---------------------------------------------------------+--------------------------------------+-------------+------------+----------+
Total files : 57
Total size : 16.748 GB
Total events : 4046640