Page 194 - DCAP405_SOFTWARE_ENGINEERING

Unit 11: Testing Strategies

11.5.1 Levels of Testing Notes

Unit Testing
In unit testing, the analyst tests the program making up a system. For this reason, unit testing is
sometimes called program testing. Unit testing gives stress on the modules independently of
one another, to find errors. This helps the tester in detecting errors in coding and logic that are
contained within that module alone. The errors resulting from the interaction between modules
are initially avoided. For example, a hotel information system consists of modules to handle
reservations; guest check in and checkout; restaurant, room service and miscellaneous charges;
convention activities; and accounts receivable billing. For each, it provides the ability to enter,
modify or retrieve data and respond to different types of enquiries or print reports. The test
cases needed for unit testing should exercise each condition and option.

Unit testing can be performed from the bottom up, starting with smallest and lowest level
modules and proceedings one at a time. For each module in bottom-up testing a short program
is used to execute the modules and provided the needed data, so that the modules is asked to
perform the way it will when embedded within the larger system.

System Testing

The important and essential part of the system development phase, after designing and
developing the software is system testing. We cannot say that every program or system design
is perfect and because of lack of communication between the user and designer, some error is
there in the software development. The number and nature of errors in a newly designed system
depend on some usual factors like communication between the user and the designer; the
programmer’s ability to generate a code that reflects exactly the systems specifications and the
time frame for the design.
Theoretically, a newly designed system should have all the parts or sub-systems are in working
order, but in reality, each sub-system works independently. This is the time to gather all the sub-
system into one pool and test the whole system to determine whether it meets the user
requirements. This is the last change to detect and correct errors before the system is installed
for user acceptance testing. The purpose of system testing is to consider all likely variations to
which it will be subjected and then push the system to its limits.
Testing is an important function of the success of the system. System testing makes a logical
assumption that if all the parts of the system are correct, the goal will be successfully activated.

Notes Another reason for system testing is its utility as a user-oriented vehicle before
implementation.

System Testing consists of the following five steps:
1. Program Testing: A program represents the logical elements of a system. For a program to
run satisfactorily, it must compile and test data correctly and tie in properly with other
programs. It is the responsibility of a programmer to have an error free program. At the
time of testing the system, there exist two types of errors that should be checked. These
errors are syntax and logical. A syntax error is a program statement that violates one or
more rules of the language in which it is written. An improperly defined field dimension
or omitted key words are common syntactical errors. A logical error, on the other hand,
deals with incorrect data fields out of range items, and invalid combinations. Compiler

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