The Aurora source repository and distributions contain several binary files to qualify the backwards-compatibility of thermos with checkpoint data. Since thermos persists state to disk, to be read by other components (the GC executor and the thermos observer), it is important that we have tests that prevent regressions affecting the ability to parse previously-written data.
The files included represent persisted checkpoints that exercise different features of thermos. The existing files should not be modified unless we are accepting backwards incompatibility, such as with a major release.
It is not practical to write source code to generate these files on the fly, as source would be vulnerable to drift (e.g. due to refactoring) in ways that would undermine the goal of ensuring backwards compatibility.
The most common reason to add a new checkpoint file would be to provide coverage for new thermos features that alter the data format. This is accomplished by writing and running a job configuration that exercises the feature, and copying the checkpoint file from the sandbox directory, by default this is /var/run/thermos/checkpoints/<aurora task id>.