Analyze the following highly simplified procedure:
Ask: "What type of ticket do you require, single or return?" IF the customer wants "return" Ask: "What rate, Standard or Cheap-day?" IF the customer replies "Cheap-day" Say: "That will be 11:20" ELSE Say: "That will be 19:50" ENDIF ELSE Say: "That will be 9:75" ENDIF
Now decide the minimum number of tests that are needed to ensure that all the questions have been asked, all combinations have occurred and all replies given.
The answer is 3. Please help with this: why the answer is 3? I do not know to justify.