Section 5.2. Testing Lists Whose Order Is Important

5.2. Testing Lists Whose Order Is Important

Here's the business rule for discount groups, our second example.

The discount percentage that is provided depends on a customer's projected future value (high, medium, low), how much is owed, and the total amount of any one purchase. As the specifics of discount groups will change from time to time, their defining values will be stored in a configuration file.

This description is not easy to follow, a situation that often arises with requirements documents. We'll see that the following examples in this chapter and in the next will help clarify what's really required.

At this stage, we simply check that the current discount groups are stored in order, as expected, in the file. The fixture DiscountGroupOrderedList, a RowFixture, is named in the first row of Figure 5.7. The header row labels the five expected field values of each element in the list, from order to discount percent.

Figure 5.7. RowFixture Table That Tests Order Explicitly

DiscountGroupOrderedList
order	future value	max owing	min purchase	discount percent
1	low	0.00	0.00	0
2	low	0.00	2000.00	3
3	medium	500.00	600.00	3
4	medium	0.00	500.00	5
5	high	2000.00	2000.00	10

We have included a column order here to be explicit about the order of the elements in the file. (This value doesn't occur in the file, so it is added by the fixture.) Fit runs the table and compares the table rows with the elements of the list in the system under test. The report resulting from Figure 5.7 is shown in Figure 5.8.

Figure 5.8. Report

Questions & Answers

Q1:

What if two rows in the table are the same?

A1:

That's OK. There would need to be two matching rows in the actual list for the test to pass.

Q2:

Does the order of the columns in the table have to match the order of the values in the actual collection?

A2:

No. And it is not necessary to include all columns if they are not of interest in a particular test. This is illustrated by Figure 5.9, which passes.

Figure 5.9. Table That Tests Some Column Values

DiscountGroupArrayList
discount percent	future value
0	low
3	low
3	medium
5	medium
10	high

Programmers

The fixture code for the tests here is given in Section 23.2 on p. 197.

Note

For now, we have ignored how the discount groups are changed. We have simply tested that they are all as expected at a certain point in time. In Section 6.2 on p. 43, we show a sequence of tests that checks that additions to the discount groups are stored correctly.

Note that we're not testing that the discount groups are being handled correctly when discounts are calculated in the software; other tests are needed to do that. For example, either of the "medium" discount groups may apply, but which takes priority? We take this up in Section 6.2 on p. 43.