Here is an interesting study on whether testing for multiple respiratory viruses (12 virus panel) influences physician behaviour with respect to antimicrobial use.
Influenza virus positivity was associated with shorter duration of hospitalization and appropriate antiviral management. But positivity for viruses other than influenza virus was not correlated with significantly different outcomes.
Clearly, behaviour change is complex and testing alone might not result in better antibiotic stewardship. We have seen this in other areas such as malaria and TB.