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Chapter 1: Introduction to Software Testing Software Testing

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1 Chapter 1: Introduction to Software Testing 322235 Software Testing
By Dr. Wararat Songpan (Rungworawut) Faculty of Computer Science, Department of Science, Khon Kaen University, Thailand

2 Software tester job??

3 Software tester job??

4 Software tester job??

5 Where is software tester in software development team?
Project Manager Tester Team System Analyst Programmer

6 Career path

7 Why is Software testing important to a business?
Loss of money Loss of time Damage to business reputation Injury or death

8 Why is Software Testing Important to a business?
Developer Independent tester Understands the system but, will test "gently" and, is driven by “delivery” Must learn about the system, but, will attempt to break it and, is driven by “quality”

9 “Testing”

10 Don’t care testing

11 The cost of software development phases
Cost Spent Requirements Analysis 3% Specification Design 5% Coding 7% Testing 15% (should be > 50%) Operational and Maintenance 67%**

12 7 Principles of testing 1) Testing shows presence of defects/Bugs
2) Exhaustive testing is impossible 3) Early testing 4) Defect clustering 5) Pesticide paradox 6) Testing is context depending 7) Absence – of – errors fallacy Source:

13 Principle 1: Testing shows presence of defects/Bugs
Testing can show the defects/Bugs are present, but cannot prove that there are no defects. After testing the application or product thoroughly we cannot say that the product is 100% defect free. Testing always reduces the number of undiscovered defects remaining in the software but even if no defects are found, it is not a proof of correctness.

14 Principle 2: Exhaustive testing is impossible
Testing everything including all combinations of inputs and preconditions is not possible. For example: In an application in one screen there are 15 input fields, each having 5 possible values, then to test all the valid combinations you would need 30  517  578  125  (515) tests. This is very unlikely that the project timescales would allow for this number of tests.

15 What is your test case?

16 Principle 3: Early testing
In the software development life cycle (SDLC) testing activities should start as early as possible and should be focused on defined objectives.

17 Principle 4: Accumulation of errors
There is no equal distribution of errors within one test object. The place where one error occurs, it’s likely to find some more. The testing process must be flexible and respond to this behavior.

18 Principle 5: Fading effectiveness
The effectiveness of tests fades over time. If test-cases are only repeated, they do not expose new errors. Errors, remaining within untested functions may not be discovered. In order to prevent this effect, test-cases must be altered and reworked time by time.

19 Principle 6: Testing is context depending
Testing is basically context dependent. Different kinds of sites are tested differently. For example, safety – critical software is tested differently from an e-commerce site.

20 Principle 7: False conclusion: no errors equals usable system
Error detection and error fixing does not guarantee a usable system matching the users expectations. Early integration of users and rapid prototyping prevents unhappy clients and discussions.

21 Software testing concepts
Software Testing is the process of evaluating a system or its component(s) with the intent to find that whether it satisfies the specified requirements or not. This activity results in the actual, expected and difference between their results. Software Testing is executing a system in order to identify any gaps, errors or missing requirements in contrary to the actual desire or requirements.

22 Keywords of testing Error is an fault in the program. There are different types of error are Syntax errors Logical errors Runtime errors Etc.

23 Keywords of testing Fault is the result of an error that is representation of error such as narrative text, dataflow diagrams, hierarchy charts, source code. Failure occurs when fault executes. Incident – when a failure occurs, it may or may not be readily apparent to the user(cutormer/tester). An incident is the symptom associated with a failure that alerts the user to the occurrence of a failure.

24 Bug(Programmer) = Defect(Tester)
Keywords of testing Bug is found in the development environment before the product is shipped to the respective customer. Defect is found in the product itself after it is shipped to the respective customer. Bug(Programmer) = Defect(Tester)

25 Keywords of testing ** Test Case - test case has an identity and is associated with a program behavior. A test case also has a set of input and a list of expected outputs. Expected output System Input Actual output

26 Expected output = Actual output
Keywords of testing For example: A Test Case 5,000 Withdraw 5,000 Baht Expected output = Actual output 5,000

27 Keywords of testing Verification: Are we building the system right?
The process of evaluating work-products (not the actual final product) of a development phase to determine whether they meet the specified requirements for that phase. Validation: Are we building the right system? The process of evaluating software during or at the end of the development process to determine whether it satisfies specified business requirements from users.

28 Structural and Functional View
S - Specified Behaviors P - Programmed Behaviors P Fault of commission S P S S Fault of omission Specification (expected) Program (observed) P

29 Structure and Functional View (Cont.)
2,5 Spec. but do not be tested 1,4 Spec. and Test 3,7 Test does not meet Spec. 2,6 Program is not tested 1,3 Program is under test 4,7 Test case do not have program. Specification (expected) Program (observed) S P 2 6 5 1 4 3 7 8 T Test cases (verified)

30 Software testing methods
Black Box Testing (Functional Testing) The technique of testing without having any knowledge of the interior workings of the application is Black Box testing. The tester is oblivious to the system architecture and does not have access to the source code. Typically, when performing a black box test, a tester will interact with the system's user interface by providing inputs and examining outputs without knowing how and where the inputs are worked upon.

31 Comparing Functional Test Case Identification Methods
Test cases (Method A) Test cases (Method B) Black box Black box

32 Software testing methods
White box testing (Structural Testing) White box testing is the detailed investigation of internal logic and structure of the code. White box testing is also called glass testing or open box testing. In order to perform white box testing on an application, the tester needs to possess knowledge of the internal working of the code. The tester needs to have a look inside the source code and find out which unit/chunk of the code is behaving inappropriately.

33 Comparing Structural Test Case Identification Methods
Test cases (Method A) Test cases (Method B) White box White box

34 Level of Testing (Waterfall model)
User Acceptance Testing Software Development Life Cycle Requirements & Specification Design test scripts/test cases System Testing Execute Preliminary Design Design Integration Testing Execute Detailed Coding Design Unit Testing Execute test scripts/test cases Coding

35 Requirements Phase Testing Activities
A preliminary analysis, propose alternative solutions, describe costs and benefits and submit a preliminary plan with recommendations. Defines project goals into defined functions and operation of the intended application. Analyzes end-user information needs. We can design overall System testing wait for actual system.

36 Design Phase Testing Activities
Describes desired features and operations in detail, including screen layouts, business rules, process diagrams, pseudo-code and other documentation. Plan to test in Unit testing and Integration testing

37 Coding Phase Testing Activities
The real code is written here then checks for error or bugs for each functions which are called Unit testing.

38 Maintenance Phase Testing
The final stage of software development, where the software is put into production and runs actual business. Brings all the pieces together into a actual environment and user, verify and validation for errors, bugs and interoperability. This testing phase is called User Acceptance Testing (UAT).

39 What the customer really needed: Must be tested

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