An important element of the scientific method is that hypotheses must be testable, potentially falsifiable, to be scientific. That we build theories by testing hypotheses and rejecting them if proved wrong by experiential evidence. And not just hypotheses. Prevailing theories are also constantly open to potential falsification, testing against new evidence and changing to incorporate new findings.
The concept of falsification in science was popularised by Karl Popper.
But who does this testing?
It’s not a matter of personal responsibility. A scientist who advances a new hypothesis is not just left alone to try to falsify it. After all, scientists are human too. They have their own emotions, biases, beliefs and preconceived ideas. They are just a susceptible as anyone else to adopting a blinkered approach to any such testing. In fact, most scientists probably look for experimental procedures which would show their pet hypothesis in a favourable light, rather than seek consciously to develop experiments aimed at proving their hypothesis wrong.
Mind you, even an experiment designed to confirm a hypothesis may, in the end, show it to be wrong.