Started refactor

tests/test_buffer_gpu.py

tests/test_conditional_field_access.py

tests/test_conditional_vec.py

tests/test_dot_printer.py

tests/test_dtype_check.py

tests/test_finite_differences.py

tests/test_fvm.py

tests/test_global_definitions.py

tests/test_helpful_errors.py

tests/test_jacobi_cbackend.py

tests/test_loop_cutting.py

tests/test_modulo.py

tests/test_move_constant_before_loop.py

tests/test_nodecollection.py

tests/test_random.py

tests/test_source_code_comment.py

tests/test_transformations.py

tests/test_vectorization.py