Introduction to Combinatorial Testing - Automatic Generation of Combinatorial Test Data - page 11

Very recently, Yilmaz [ 44 ] distinguishes between system-wide constraints and test
case-specific constraints, and introduces a new combinatorial object, called a test case-
aware covering array .
1.4.4 Covering Arrays with Shielding Parameters
In CT, we usually assume that all parameters of the systemunder test are always effective.
But in some real applications, there may exist some parameters that can disable other
parameters in certain conditions. A classical example is that, when we select “ -h ”(the
help option) for a command, the other options are ignored. As another example, when
we configure the TCP/IP protocol on a Microsoft Windows computer, we often need to
fill in such information as IP address , subnet mask and default gateway .
However, if we choose to obtain IP addresses automatically , these parameters are dis-
abled.
To deal with the above problems, Chen et al. [ 6 ] proposed the conceptMixedCovering
Arrays with Shielding parameters (MCAS).
1.4.5 Sequence Covering Arrays
In the classical formulation of CT, we assume that the parameters are somewhat inde-
pendent of each other, subject to some declarative constraints on the values of certain
parameters. However, in certain applications, the SUT accepts input parameters in some
order, and then produces output values. In other words, the input to the SUT is a sequence
of parameter values. When applying CAs to the testing of GUIs, Yuan et al. [ 45 ] leverage
a “stateless” abstraction of GUIs.
Recently, to deal with the above kind of applications, Kuhn et al. [ 21 ] proposed the
so-called sequence CAs. Such an array can be used to test the interactions of input
sequences.
1.4.6 An Example of Using Covering Arrays for Testing
Now we give an example of using CAs for CT. We slightly modify the web application
testing example that we mentioned earlier. There are four parameters/components in the
system, which are shown in Table 1.1 .
Since some web browsers can only be installed on specific operating systems, we
need to write the following constraints to exclude invalid combinations:
Browser =="Internet Explorer" -> OS == "Microsoft Windows"
Browser == "Safari" -> OS == "Mac OS X"