8.10 Choose a hypothesis from historical data

The following heuristics can be used to select a hypothesis from historical records and general knowledge about the programming language being used:

The error is the one the programmer makes most often.
The error is one of the most common errors made when coding in this language.
The error is one of the most common errors made regardless of programming language.
The error is in the most recently changed code.
The error is the easiest hypothesis to evaluate.

Choosing a hypothesis from historical data is appropriate when you have been working on a defect for some time and you’re running out of hypotheses.

If you want to choose as a hypothesis that the problem is one that the programmer makes frequently, you need records on the root causes of previous defects diagnosed in the system in question. If you want to choose as a hypothesis that the problem is one of the most common errors made when using the particular programming language selected for this application, consult an error checklist from a programming text, or Appendix A.

If you want to choose as a hypothesis that the problem is one of the most common errors made by all programmers, you might find it useful to consult Chapter 11. If you want to choose as a hypothesis that the problem is in recently changed code, you need to have been using a source control system.