I'm putting together a test plan to test a logic engine that takes input from a user in forms of answers to mainly closed questions. The engine then evaluates the answers against certain rules and concludes if the input makes them eligible or ineligible. Depending on the answer, there are further drill down questions which can go an extra 2 levels deep and can have up to 5 options for each. Essentially, there's a huge amount of routes and combinations that the user can go through and input.
The primary feature I want to test is the logic in that it evaluates the inputs correctly based upon the rules there are. The system works by taking the questions in three stages, and evaluates at each stage, so I also need to test that it evaluates correctly at each of these stages, and won't allow a user to progress further than they should, even if they are eventually evaluated correctly at a further stage.
I'm doing this manually, and don't have any testing software available to me so will be doing this in Excel.
I'm planning to use the pairwise method to get the most test coverage with the least input combinations, but it's still going to result in a huge amount of combinations.
Any guidance/ advice on this would be helpful.
Edit: Including drill down questions, there are 727 questions.