Extend testsuit

.gitlab-ci.yml

pystencils/backends/cbackend.py

pystencils/backends/cuda_backend.py

pystencils/backends/json.py

pystencils/backends/opencl_backend.py

pystencils/datahandling/pycuda.py

pystencils/datahandling/pyopencl.py

pystencils/fd/derivation.py

pystencils/fd/finitedifferences.py

pystencils/fd/finitevolumes.py

pystencils/gpucuda/cudajit.py

pystencils/gpucuda/texture_utils.py

pystencils/jupyter.py

pystencils/opencl/opencljit.py

pystencils_tests/test_datahandling.py

pystencils_tests/test_fd_derivation_via_rotation.ipynb

pystencils_tests/test_finite_differences.py

pystencils_tests/test_json_backend.py

pystencils_tests/test_jupyter_extensions.ipynb

pystencils_tests/test_llvm.py