Error guessing is known to be one way of knowing the error from previous experiences. however, it's a technique that usually testers perform if all other formal techniques (like Whitebox testing or other blackbox testing) failed to identify the error.
Scenario: Assuming that I have automatic bus door that opens once the bus arrives at the station for people with disabilities.
My question is as follows: What kind of errors can take place (in the scenario above) and can be detected only by guessing not any other formal techniques?
Thanks..
There are no errors that cannot be found with formal techniques, at least in theory. It is just difficult to generate all relevant test cases and achieve 100% test coverage. The point of error guessing is to use experience and heuristics to find a few test cases that are likely to fail while still ignoring many other test cases which are not.