
Test Generation from Combinatorial Designs
to assume levels from different sets. A mixed-level covering array is
denoted as MCA(N, s
k
1
1
s
k
2
2
...s
k
p
p
, t) and refers to an N × Q matrix
of entries such that Q =
p
i=1
k
i
, and each N × t subarray contains at
least one occurrence of each t-tuple corresponding to the t columns.
Mixed-level covering arrays are generally smaller than mixed-
level orthogonal arrays and more appropriate for use in software test-
ing. The next example shows MCA(6, 2
3
3
1
, 2). Comparing this with
MA(12, 2
3
3
1
, 2) from Example 4.20, we notice a reduction of six test
inputs.
Run Size Toppings Address Phone
11 1 1 1
22 2 1 2
33 1 2 2
41 2 2