Section 18.5. List Tests

18.5. List Tests

We now focus on design ideas and smells that apply to list tests expressed with RowFixture, ArrayFixture, and SubsetFixture.

18.5.1. Smell: Too Many List Columns

Consider the Fit table shown in Figure 18.15, which is checking that the count of items is correct. Several columns are irrelevant to this test, adding unecessary and distracting detail. We can improve this table by eliminating the irrelevant columns, as shown in Figure 18.16.

Figure 18.15. Many List Rows

rental items list
name	count	hourly rate	daily rate	weekly rate	deposit
coffee urn	10	1.50	12.00	60.00	50.00
table	20	6.00	48.00	200.00	80.00
coffee pot	20	1.50	12.00	60.00	0.00
chair	20	6.00	48.00	200.00	0.00

Figure 18.16. Fewer Columns

rental items list
name	count
coffee urn	10
table	20
coffee pot	20
chair	20

In general, if a Fit table for testing lists has many columns, consider whether all of them are relevant to the test. For example, you may decide to include just those columns that are expected to change or those that are expected to not change.

18.5.2. Smell: Too Many List Rows

Suppose that we are interested only in the number of coffeee urns. Then the table in Figure 18.16, as discussed in Section 18.5.1, contains more detail than necessary. The SubsetFixture table shown in Figure 18.17 can then be used to focus on the number of that one rental item.

Figure 18.17. Fewer Rows with SubsetFixture

rental item subset
name	count
coffee urn	10

Another approach to reducing irrelevant detail is to select some of the elements of the list. For example, the test in Figure 18.18 uses an argument, Joanna, to focus on a single client's rentals, avoiding the need to list the rentals of all clients.

Figure 18.18. Fewer Rows, Using Arguments

rentals for client	Joanna
rental item	count	start date	end date
cup	100	2004/05/06 09:01	2004/05/20 09:01