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ABC of Unit Testing

What is Unit Testing? After writing any code, every programmer will do some kind of testing to make sure the code works as expected. This testing is called 'unit testing'. Unit testing is done in different ways. Some programmers write simple test applications to test their own code. Some others simply debug the code and change the values during debugging to make sure the code works fine for different cases. Some facts about unit testing: Unit testing is done by developers. Quality department does different tests, they are not unit tests. Every programmer must do unit testing after finishing development or during development itself. Unit testing can be done by writing separate test applications to call your classes and methods to make sure the classes work as expected. This is called manual unit testing. Unit testing can be automated by writing unit test scripts. This is called Automated Unit Testing. In automated Unit Testing, after writing each class/method, you will write sev...
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History - Software Testing

Do you know who distinguish testing from debugging? The separation of debugging from testing was initially introduced by Glenford J. Myers in 1979. Although his attention was on breakage testing ,it illustrated the desire of the software engineering community to separate fundamental development activities, such as debugging, from that of verification. Dr. Dave Gelperin and Dr. William C. Hetzel classified in 1988 the phases and goals in software testing in the following stages: Until 1956 - Debugging oriented 1957-1978 - Demonstration oriented 1983-1987 - Destruction oriented 1983-1987 - Evaluation oriented 1988-onward- Prevention oriented References: Myers, Glenford J. (1979). The Art of Software Testing. John Wiley and Sons. ISBN 0-471-04328-1 . Gelperin, D.; B. Hetzel (1988). "The Growth of Software Testing". CACM 31 (6). ISSN 0001-0782. until 1956 it was the debugging oriented period, when testing was often associated to debugging: there was no clear difference between te...
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What is Software Testing?

Software testing is any activity aimed at evaluating an attribute or capability of a program or system and determining that it meets its required results. [Hetzel88] Although crucial to software quality and widely deployed by programmers and testers, software testing still remains an art, due to limited understanding of the principles of software. The difficulty in software testing stems from the complexity of software: we can not completely test a program with moderate complexity. Testing is more than just debugging. The purpose of testing can be quality assurance, verification and validation, or reliability estimation. Testing can be used as a generic metric as well. Correctness testing and reliability testing are two major areas of testing. Software testing is a trade-off between budget, time and quality. Software Testing is the process of executing a program or system with the intent of finding errors. [Myers79] Or, it involves any activity aimed at evaluating an attribute or cap...
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Why to do Software Testing?

Regardless of the limitations, testing is an integral part in software development. It is broadly deployed in every phase in the software development cycle. Typically, more than 50% percent of the development time is spent in testing. Testing is usually performed for the following purposes: To improve quality. As computers and software are used in critical applications, the outcome of a bug can be severe. Bugs can cause huge losses. Bugs in critical systems have caused airplane crashes, allowed space shuttle missions to go awry, halted trading on the stock market, and worse. Bugs can kill. Bugs can cause disasters. The so-called year 2000 (Y2K) bug has given birth to a cottage industry of consultants and programming tools dedicated to making sure the modern world doesn't come to a screeching halt on the first day of the next century. [Bugs] In a computerized embedded world, the quality and reliability of software is a matter of life and death. Quality means the conformance to the ...
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Types of Testing

There is a plethora of testing methods and testing techniques, serving multiple purposes in different life cycle phases. Classified by purpose, software testing can be divided into: correctness testing, performance testing, reliability testing and security testing . Classified by life-cycle phase, software testing can be classified into the following categories: requirements phase testing, design phase testing, program phase testing, evaluating test results, installation phase testing, acceptance testing and maintenance testing . By scope, software testing can be categorized as follows: unit testing, component testing, integration testing, and system testing. Correctness testing Correctness is the minimum requirement of software, the essential purpose of testing. Correctness testing will need some type of oracle, to tell the right behavior from the wrong one. The tester may or may not know the inside details of the software module under test, e.g. control flow, data flow, etc. There...
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When to Stop Testing

Testing is potentially endless. We can not test till all the defects are unearthed and removed -- it is simply impossible. At some point, we have to stop testing and ship the software. The question is when. Realistically, testing is a trade-off between budget, time and quality. It is driven by profit models. The pessimistic, and unfortunately most often used approach is to stop testing whenever some, or any of the allocated resources -- time, budget, or test cases -- are exhausted. The optimistic stopping rule is to stop testing when either reliability meets the requirement, or the benefit from continuing testing cannot justify the testing cost. [Yang95] This will usually require the use of reliability models to evaluate and predict reliability of the software under test. Each evaluation requires repeated running of the following cycle: failure data gathering -- modeling -- prediction. This method does not fit well for ultra-dependable systems, however, because the real field failure ...
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Alternatives to testing

Software testing is more and more considered a problematic method toward better quality. Using testing to locate and correct software defects can be an endless process. Bugs cannot be completely ruled out. Just as the complexity barrier indicates: chances are testing and fixing problems may not necessarily improve the quality and reliability of the software. Sometimes fixing a problem may introduce much more severe problems into the system, happened after bug fixes, such as the telephone outage in California and eastern seaboard in 1991. The disaster happened after changing 3 lines of code in the signaling system. In a narrower view, many testing techniques may have flaws. Coverage testing, for example. Is code coverage, branch coverage in testing really related to software quality? There is no definite proof. As early as in [Myers79] , the so-called "human testing" -- including inspections, walkthroughs, reviews -- are suggested as possible alternatives to traditional testin...
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