
Basics of Software Testing
)LJ PDG for Program P1.3.
1.17 STRINGS, LANGUAGES, AND REGULAR EXPRESSIONS
Strings play an important role in testing. As we shall see in Section 3.2,
Chapter 3, strings serve as inputs to a FSM and hence to its implemen-
tation as a program. Thus a string serves as a test input. A collection of
strings also forms a language. For example, a set of all strings consisting
of zeros and ones is the language of binary numbers. In this section we
provide a brief introduction to strings and languages.
A collection of symbols is known as an alphabet. We will use up-
percase letters such as X and Y to denote alphabets.