fixing unit tests to properly test imported units refs
fixing unit tests to properly test imported units refs

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