Page 266 - DCAP305_PRINCIPLES_OF_SOFTWARE_ENGINEERING

Principles of Software Engineering

Notes IEEE Definitions
Failure: External behaviour is incorrect
Fault: Discrepancy in code that causes a failure

Error: Human mistake that caused fault
Note

Error: is terminology of Developer
Bug: is terminology of Tester.

13.2 Test Oracles

The oracle problem is addressed for chance testing and difficult of randomized software. The
presented Statistical Oracle is a Heuristic Oracle using statistical methods, especially statistical
tests. The Statistical Oracle is applicable in case there are explicit formulae for the mean, the
distribution, and so on, of characteristics computable from the test result. As with the Heuristic
Oracle, the decision of the Statistical Oracle is not always right. The Statistical Oracle has
successfully been functional. To test any program, we need to have a description of its expected
behaviour and a method of determining whether the observed behaviour conforms to the
expected behaviour. For this we need a test oracle. A test oracle is a mechanism, different from
the program itself, which can be used to check the correctness of the output of the program for
the test cases. Conceptually, we can consider testing a process in which the test cases are given
to the test oracle and the program under testing. The output of the two is then compared to
determine if the program behaved correctly for the test cases. Test designers widely believe that
the overall effectiveness and cost of software testing depends largely on the type and number of
test cases executed on the software. Test oracle used during testing also contributes significantly
to test effectiveness and cost. A test oracle is a mechanism that determines whether software
executed correctly for a test case. We define a test oracle to contain two essential parts, oracle
information that represents expected output, and an oracle procedure that compares the oracle
information with the actual output. By varying the level of detail of oracle information and
changing the oracle procedure, a test designer can create different types of test oracles.
13.3 Test Cases and Criteria

Test case and criteria for testing is given blow:
13.3.1 Test Cases

A test case is a documentation which specifies input principles, expected output and the
preconditions for executing the test or a test case is a scenario made up of a sequence of steps
and conditions or variables, where test inputs are provided and the program is run using those
inputs, to see how it performs. An expected result is outlined and the actual result is compared to
it. Certain working conditions are also present in the test case, to see how the program handles
the conditions. Every requirement or objective that the program is expected to achieve, needs
at least one test case. Realistically, it definitely takes more than one test case to determine the
true functionality of the application being tested. The mechanism used to judge the result of the
test case, i.e. whether the program has failed or passed the test, is called a test oracle. Test cases,
at root level, are used to measure how a program handles errors or tricky situations such as if
one input is incorrect or if both inputs are incorrect. They are also expected to expose hidden
logical errors in the program’s code that have gone undetected.

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