Section 15.5. Sad Paths

15.5. Sad Paths

Don was eager to focus on "when the transaction can't complete." In testing, this is often called a sad path because it concerns what happens when things don't work out well. After discussion and a few trials, the group came up with the first sad-path test, as shown in Figure 15.11.

Figure 15.11. Testing a Transaction That Can't Complete

begin transaction for client	Joanna	staff	Bill
rent	100		cup	for	2	weeks
reject	complete transaction
pay with cash $	210.00
complete transaction

No payment has been made in the third row of Figure 15.11. So the complete transaction in the third table must be rejected by the system under test. Once the payment has been made in the fourth row, the transaction can be completed.

The group wrote 20 more sad-path tests for complete and cancel transactions, including the one shown in Figure 15.12. A transaction can't be canceled until any paid money is refunded.

Figure 15.12. Testing a Transaction That Can't Be Canceled

begin transaction for client	Joanna	staff	Bill
rent	100		cup	for	2	weeks
pay with cash$	410.00
reject	cancel transaction
refund cash$	410.00
cancel transaction

Questions & Answers

Q1:

But doesn't the test in Figure 15.11 consist of two tests?

A1:

Yes, you're right, with the first test simply checking that the complete transaction was rejected. We also need to check that a previously rejected completion of a transaction can be completed later. However, the test is so short that splitting it into two doesn't seem worthwhile, especially as there are no other cases yet. There's usually a judgment call and often a tradeoff in such decisions, and people differ in their approach to this issue.