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This section covers different methods to make small xtc test files. Presently the largest xtc test file in data_test is about 1GB, which is bigger than it needs to be. I think we should be able to keep test files down to 20-100 MB, smaller files mean faster unit tests as well.

Using psana_test

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Psana_test includes a library of Python code with a function to copy out a few datagrams from each xtc file for a run. An example of use is

Code Block
language python
import psana_test.psanaTestLib as ptl ptl.copyToMultiTestDir('cxie9214',63,1,2,'/reg/g/psdm/data_test/multifile/test_012_cxie9214')

For experiment cxie9214, run 64, 1 calib cycle, the first 2 events from this calib cycle (for each stream) are copied into xtc files with the same name in the given directory. Moreover a 'index' subdirectory will be made and index files will be written there.

Using xtclinedump

Before writing that function, I would do things by hand. Suppose we want some test data for Epix100aConfig. We know it is somewhere in this file:For the testing that I have done, I typically want to run psana on a few datagrams in an xtc file to test how it parses a new type or handles some damaged data. Suppose we don't have unit tests to see how psana handles Epix100aConfig version1 and EpixElement version 2, and we have identified an experiment xtc file with these types, namely

/reg/d/psdm/xcs/xcsi0314/xtc/e524-r0213-s03-c00.xtc

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