Generator test: update it to use our "new" processModel() method.
Generator test: update it to use our "new" processModel() method.

cellml/libcellml,nickerso/libcellml,nickerso/libcellml,hsorby/libcellml,nickerso/libcellml,cellml/libcellml,MichaelClerx/libcellml,hsorby/libcellml,hsorby/libcellml,MichaelClerx/libcellml,cellml/libcellml,cellml/libcellml,nickerso/libcellml,hsorby/libcellml,MichaelClerx/libcellml