CSE
What is Software design.docx

Fault when error exists fault occurs a fault also

Info icon This preview shows pages 4–7. Sign up to view the full content.

Fault - When error exists fault occurs. A fault, also known as a bug, is a result of an error which can cause system to fail. Failure - failure is said to be the inability of the system to perform the desired task. Failure occurs when fault exists in the system. Test cases and Test suites A test case is a triplet [I,S,O] o I is the data to be input to the system, o S is the state of the system at which the data will be input, o O is the expected output of the system.
Image of page 4

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

Test software using a set of carefully designed test cases. The set of all test cases is called the test suite Design of Test Cases o Complete testing of any nontrivial system is invalid if input data domain is extremely large. o Design an optimal test suite of reasonable size and uncovers as many errors as possible o If test cases are selected randomly would not detect errors not already being detected by other test cases in the suite. o Testing a system using a large number of randomly selected test cases Example for finding the maximum of two integers x and y. The code has a simple programming error: If (x>y) max = x; else max = x; test suite {(x=3,y=2);(x=2,y=3)} can detect the error, a larger test suite {(x=3,y=2);(x=4,y=3); (x=5,y=1)} does not detect the error. There are two main approaches to design test cases: o Black-box approach o White-box (or glass-box) approach Black-box: In black-box testing can design test cases without any knowledge of the internal structure of the software. Black-box testing is also known as functional testing. There are two main approaches to design black box test cases: o Equivalence class - The input is divided into similar classes. If one element of a class passes the test, it is assumed that all the class is passed. o Boundary values - The input is divided into higher and lower end values. If these values pass the test, it is assumed that all values in between may pass too. White-box: In White-box testing for design test cases requires knowledge about the internal structure of software. White-box testing is also called structural testing.
Image of page 5
Testing Software products are tested at three levels: o Unit testing o Integration testing o System testing Unit Testing While coding, the programmer performs some tests on that unit of program to know if it is error free. Testing is performed under white-box testing approach. Unit testing helps developers decide that individual units of the program are working as per requirement and are error free. Integration Testing Even if the units of software are working fine individually, there is a need to find out if the units if integrated together would also work without errors. For example, argument passing and data updation etc.
Image of page 6

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

Image of page 7
This is the end of the preview. Sign up to access the rest of the document.
  • Fall '17
  • Mr. Iqbal
  • o Software

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern