New 137-line test file included in main test/runtests.jl:
- Tests extract_strain() function (displacement gradient → strain tensor)
- Tests extract_strain_rate() function (velocity gradient → strain rate tensor)
- Tests pure extension, shear deformation, and general deformation cases
- Tests quasi-static strain rate from increments
- Validates symmetric tensor properties and engineering shear strain
Ensures strain extraction functions work correctly for continuum mechanics.
Jukka Aho