XSLT Cookbook

Testing Boundary and Error Conditions

Problem

You are writing utility templates to be used by others, and you want them to be robust.

Solution

Boundary-condition testing

In all programming languages, bugs most often appear at boundary conditions. Thus, you should choose test data in which values lie along data extremes. Boundary values include maximum, minimum, and just inside/outside boundaries. If your templates work correctly for these special values, then they will probably work correctly for all other values. It is impossible to provide an exhaustive list of boundary conditions because they vary from problem to problem. Below is a list of typical cases you should consider.

If a template acts on node sets, then be sure to test the following cases:

• An empty node set

• A node set with one element

• A node set with two elements

• A node set with an odd number of elements other than 1

• A node set with an even number of elements other than 2

If a template acts on a string, be sure to test the following cases:

• The empty string

• A string of length 1

• Other strings of varying sizes

If your template uses substring-before or substring-after for searches, be sure to test the following cases:

• Strings that do not contain the test string

• Strings that start with the search string

• Strings that end with the search string

• Strings that contain only the search string

If a template acts on numbers, be sure to test:

• The number 0

• The number 1

• Negative numbers

• Fractional numbers (0 < x < 1)

• Numbers with whole and fractional ...