Some important things missing. One has to define what a bug is. For example, I have many times received a bug report for something that was perfectly normal sy

Some important things missing. One has to define what a bug is. For example, I have many times received a bug report for something that was perfectly normal system behaviour. The reasons for this are varied from users not understanding the system, the system behaviour being complex and causing emergent phenomena that is strange at first sight but completely fine when you start to analysing it to consequences of underspecified requirements, broken communication at the time of requirement gathering, etc. It might still result in a bug, but this time a bug report for the original design. Another very important thing missing is it is absolutely crucial to gather from the user what was the expected outcome. I can't begin to tell you how many times I had a developer "fix" the bug only to find out the fix is not what the user wanted to happen. Or that there wasn't even a bug in the first place and the fix actually broke the system for somebody else. As to the forming and testing the hypothesis, the missing is that you can do it all by reading, understanding the code and simulating the problem all in your mind. I have probably fixed something like 70-80% of all bugs at this stage. What you do is you form a hypothesis and then you start tracing the pieces of data through the code of the application (aided by your understading of it). If I can find something in the code that disproves my hypothesis, I have now saved time on setting up the whole test. But I also gained more understanding of the problem which I would probably not if I just let the application fail. Even if I actually found a solution, I can have better understanding how the piece of data interacts with parts of the system and I may now be aware how to write the fix or at the very least how to do it better.