Some tests of breatharians have simply isolated and watched the person for a period of time. For example Prahlad Jani and Hira Ratan Manek.
The reason I am so sceptical of such tests when performed by doctors, is that the first thing any doctor should want to do is a thorough physical examination. In the previous posts I have suggested a number of possible tests which a doctor could perform, which would all but prove whether a person is or isn't living without food.
To any genuine breatharian, such physical tests should seem by far preferable, for some of the following reasons. First, being locked up and watched for weeks or months on end is extremely invasive of a person's privacy, and extremely demanding on a person's time. Allowing a doctor to take blood samples, scans and xrays, on the other hand, should take up less than a day of their time.
What is more, many people are very sceptical of tests which lock people away, as it would be easy for an accomplass to slip the 'breatharian' food. Even with CC TV watching the person 24 hours a day, a dodgy doctor who was an accomplass could easily put the tv on a loop while the 'breatharian' was in bed, and then the breatharian could be given food, water, and allowed to go to the loo. Safely back in bed, the CC TV could be made live again. It would probably take just one dishonest accomplass on a team of honest doctors. There are many other ways the test could be rigged, this is just one. A genuine breatharian should want to run from this kind of test, as they bring so much scepticism.
Such tests are also expensive - mainly due to paying people's wages for months to watch the person.
What is more, if anyone more sceptical wanted to repeat the 'isolate for weeks' test, it would again take up a large block of the breatharian's life. The difficulty of repeating tests may be another source for scepticism, as subjects probably wouldn't want to go through the experience twice.
But for a physical examination, if there really were unusual results found, such as the breatharian not breathing out carbon dioxide, repeat tests could be performed with little disturbance to the person tested. Physical tests should be far cheaper, easier, and less intrusive on breatharians, as well as providing more solid evidence. What is more, the results would be far more useful to truly advance science and understand human potential, than simply seeing if someone can live without food and drink when isolated.