Create a junit file for each class as soon as the generation of its test sequences is completed

[rachelt44]

Is your feature request related to a problem? Please describe.

Currently test files are written only at the end of the generation process, i.e., after test sequences were generated for all classes. If the extender process crashes for some reason, we are left with no junit tests.

Describe the solution you'd like

The extender should export test sequences as a junit file for each class upon completing its processing.

Describe alternatives you've considered

A clear and concise description of any alternative solutions or features you've considered.

Additional context

Add any other context or screenshots about the feature request here.

[sinha108]

Implemented via issue konveyor/tackle-test-generator-core#105