大陆 - 软件测试策略.ppt

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1、Software Testing Strategies,2 / Daniel Grigoroscuta / 07.02.2008 Continental AG,What is testing? What is quality? Why is testing necessary? What are defects and what causes errors? Types of testing,Agenda,3 / Daniel Grigoroscuta / 07.02.2008 Continental AG,What is Testing? - Exercise,Audition Breath

2、alyzer test Driving test Eye test Final exam after faculty IQ test Spelling test Test driving a car Test paper What do these tests tell us about the software test process?,4 / Daniel Grigoroscuta / 07.02.2008 Continental AG,What is Testing?,These tests have different elements of: Planning and prepar

3、ation Known goals including pass/fail criteria and risk assessment Judging and evaluation Measurement during a controlled test Report back on the outcome Action as result of the outcome,5 / Daniel Grigoroscuta / 07.02.2008 Continental AG,What is Software testing?,Software testing is a process of ver

4、ifying and validating that a software application: - Meets the business and technical requirements that guided its design and development - Works as expected. Software testing has three main purposes: verification, validation, and defect finding. - The verification process confirms that the software

5、 meets its technical specifications. Compliance with requirements. - The validation process confirms that the software meets the business requirements. Fitness for expected use. - A defect is a variance between the expected and actual result. It may be a bug (error in the code) or a fault in the spe

6、cification, design phase. Above all of this a tester main goal should be to provide information to the people in charge with the project: - test plans, tests results, tests coverage, data from stress, performance, experience based tests etc. Software testing is a Measurement of software quality,6 /

7、Daniel Grigoroscuta / 07.02.2008 Continental AG,What is Quality?,If testing measures software quality, then. what is quality?,7 / Daniel Grigoroscuta / 07.02.2008 Continental AG,What is Quality?,Possible definitions: Product based: quality characteristics User based: “fitness” for use Manufacturing

8、based: conformance to requirements Value based: balancing with time and money,Software quality,According to ISO/IEC 9126 software quality consists of: - Functionality (correctness and completeness) - Reliability (fault tolerance, recover after failure) - Usability (intuitive handling, easy to learn)

9、 - Efficiency (e.g. the system requires a minimal use of resources (e.g. CPU-Time) - Maintainability (how easy the system can be maintained, improved) - Portability (ability to transfer the software to a new environment) Types of Quality Assurance (QA) - constructive activities to prevent defects, e

10、.g. through appropriate methods of software engineering - analytical activities for finding defects, e.g. through testing leading to correcting defects and preventing failures, hence increasing the software quality,QA vs. Testing,Software Quality Assurance - Software QA involves the entire software

11、development PROCESS: monitoring and improving the process, making sure agreed upon standards and procedures are followed, and ensuring that problems are found and dealt with. It is oriented towards prevention. Software Testing - Testing involves operation of a system or application under controlled

12、conditions and evaluating the results. The controlled conditions should include both normal and abnormal conditions. It is oriented towards detection Testing is to create, run, verify test cases to see if the proper behavior was observed. QA is to examine the whole process to minimize risk. Risk due

13、 to specs/requirements, implementation, follow-up. Testing is a part of the QA role, but the QA role extends much further than just focusing on testing.,10 / Daniel Grigoroscuta / 07.02.2008 Continental AG,Whats the need of testing?,We all make mistakes. Crucial for business survival: save money in

14、the long run (maintenance etc.) reputation and reliability lawsuits Increasing importance and size of software in society as a whole Defects hardly decrease,What are the causes of software failures?,Human error A defect was introduced into the software code, the data or the configuration parameters

15、Causes of human error time pressure, excessive demands because of complexity, distractions, not enough knowledge, bad communication etc Environmental conditions changes of environmental conditions Causes of negative environmental conditions radiation, magnetism, electronic fields and pollution sun s

16、pots, hard disk crashes, power fluctuations etc.,12 / Daniel Grigoroscuta / 07.02.2008 Continental AG,What are Software Defects?,Bugs vs. Defects Bug: (1) things the software does that it is not supposed to do, or something the software doesnt do that it is supposed to; (2) a fault in a program whic

17、h causes the program to perform in an unintended or unanticipated manner. Defect: (1) (IEEE) a product anomaly; (2) synonymous with error, implies a quality problem discovered after the software has been released to end-users (or to another activity in the software process); (3) fault; (4) error, fa

18、ult, or failure; (5) non conformance to requirements. Question: What do we mean by zero defects?,Test levels,During the software life cycle several test levels are found Component testing (also known as module, unit, class or developers test) Integration testing (also interface testing) System testi

19、ng Acceptance testing,Component testing,Test of each component after realization is made by the developer Every component is tested on its own finding failures caused by internal defects cross effects between components are not within the scope of this test Test cases may be derived from component s

20、pecification software design data model Testing components often requires drivers and stubs Drivers handle the interface of the component (simulate inputs, record outputs) Stubs replace or simulate components not available yet or not part of the test Source code knowledge allows to use white box met

21、hods for component tests,Component testing 2,Testing functionality Every function must be tested with at least one test case are the functions working correctly, are all specifications met? Defects found commonly are defects in processing data, often near boundary values missing functions Testing ro

22、bustness (resistance to invalid input data) Test cases representing invalid inputs are called negative tests A robust system provides and appropriate handling of wrong inputs Wrong inputs accepted in the system may produce failure in further processing (wrong output, system crash) Other non function

23、al attributes may be tested e.g. performance and stress testing, reliability,Integration testing,Examines the interaction of software components after system integration Assumes that the components have been already tested. Integration tests examine the interaction of software components (subsystems

24、) with each other: interfaces with other components interfaces among GUIs / MMIs Integration tests aim at finding defects in interfaces Test cases may be derived from interface specifications architectural design data models Different strategies are used for integration testing; bottom-up and top-do

25、wn are the most used,System test,Testing the integrated software to prove compliance with the specified requirements System tests refer to: functional and non-functional requirements (functionality, reliability, usability, efficiency etc) Test of the integrated system from the users point of view co

26、mplete and correct implementation of the requirements deployment in the real system environmentwith real life data Test environment should meet the true environment no test drivers are needed all external interfaces are tested under true conditions close representation of the later true environment

27、No tests in the real life environment defects could damaged the real life environment software under deployment is constantly changing. Most tests will not be reproducible,System test 2,Testing functionality Prove that the implemented functionality exposes the required characteristics: Suitability -

28、 are the implemented functions suitable for their expected use Accuracy - do the functions produce correct results? Interoperability - does interaction with the system environment show any problems? Compliance - does the system comply with applicable norms and regulations? Security - are data / prog

29、rams protected against unwanted access or loss?,Acceptance testing,A formal test performed in order to verify compliance with the user requirements First test where the customer is involved Customers use the software to process their daily business process at the suppliers location (alpha testing) o

30、r at their own location (beta testing) Advantages of alpha and beta tests reduce the cost of acceptance testing use different user environments involve a high number of users,Principles of all testing levels,each development activity must be tested no piece of software may be left untested each test

31、 level should be tested specifically each test level has its own test objectives the test performed at each level must reflect these objectives testing begins long before test execution as soon as development begins the preparation of the corresponding tests can start this is also the case for docum

32、ent reviews starting with concepts, specification and overall design,Roles in testing,Testing activity is such complex that several roles have been defined each of them with different responsibilities Roles: Developers also developers have to test their code Test lead/manager - effectively lead the

33、testing team Tester execute the tests and record the test results Test designer write test cases, develop test structure, perform test coverage analysis Test automation developer create automatic test scripts that will follow the designed test cases Beside that every person involved in the PLC proce

34、ss has his role in the testing process - developers have to test their code - project leaders have to test the requirements by reviewing them,Testing process Continental,Discipline (Entertainment, Navi etc.),System Integration,PVV (Product Verification and Validation),Test Result,PRODUCTION,Failed,P

35、assed,Requirements / Architecture,What are the elements that are contained by the testing process?,Test Plan Test Cases Test Suites Test Techniques,Test plan,A test plan is a formal document that describe: Scope, objectives, and the approach to testing why, what and how do we have to test People and

36、 equipment dedicated/allocated to testing who are the people responsible for tests Tools that will be used what kind of tools to use, do we need automation tests, where we will use them Dependencies and risks what other things have to take care before starting tests and what are the risks Categories

37、 of defects what are the defects categories and which kind of defects are included in each of them Test entry and exit criteria when does the test start and when does it end Measurements to be captured what kind of results do we need Reporting and communication processes what is the procedure for re

38、porting problems and for communication Schedules and milestones what are the milestones of the project and when testing should be performed Basically the Test plan describes what and how you are going to test. It is used to keep track for each steps of activities in testing. If we follow the test pl

39、an a quality product can be delivered.,Test cases,A Test case is a document that describe the process and expected result required to determine if a requirement has been satisfied. There is situations when more test cases are cover in the same document. A requirement may need several test cases to c

40、over it all. Mainly a Test Case can have the below elements: - Test case ID - Preconditions for the test case - Test case description what are we trying to test - Requirement that will be cover - Test procedure - Expected results - Actual results In many times a Test case can have more than one test

41、 step each step having his own Expected result. The process of developing test cases can help finding problems in the requirements of the application so is suggested that writing the test cases should start early in the develop cycle if possible.,Test suites,A Test suite is a collection of test case

42、s which are grouped based on one criteria or more. A system can have an unlimited number of test suites based on different criteria: - A test suite for HMI tests - A test suite for Performance tests - A test suite for Navigation tests - A test suite for Entertainment tests - etc.,Testing techniques,

43、Static code analysis mainly used by developers for a part of the program without executing the program Requirements Based Tests the most used one tests are based on the specification Scenario Based Tests based on the scenarios a real user will follow when performing a function on the system Equivale

44、nce Partitioning used to minimize the number of tests to minimum necessary (make one test for an partition) e.g. values 1.12 for month Boundary-value Analysis tests are done using the limit values e.g. for month test with 0,1,12,13 All-pairs testing used for minimizing the tests when two or more var

45、iables have to be taken into consideration http:/www.pairwise.org/articles.asp Error Guessing think where the application may have problems (also known as Risk based) Output Forcing make tests to obtain a specific output not interesting the imputs Ad-hoc tests/Exploratory tests the tests are perform

46、ed without planning/documentation (usually done only once unless bugs are found); used to quickly find the problems,Relation with the developers,“The best tester is not the one who finds the most bugs or who embarrasses the most developers. The best tester is the one who gets the most bugs fixed.” C

47、em Kaners Testing Computer Software Strategies to have a good relation with the developers: Be Cordial and Patient convincing a developer that his program has a bug is not such an easy job Be Diplomatic - try presenting your findings with tact not accusing anyone. Be sure that testers exist in the c

48、ompany because of developers and because of us their jobs are saved Dont embarrass - nobody is perfect and nobody wants mistakes to be pointed out. Just as a tester cant test a program completely, developers cant design programs without mistakes. We are human after all. Be Cautious - design your bug

49、 reports and test documents in a way that clearly lays out the risks and seriousness of issues so the developer cant say later that they didnt solved the bug because they were not aware or you Dont consider your work less important it has same importance as its work “A smart tester is one who keeps a balance between listening and implementing. If a developer cant convince you a bug shouldnt be fixed, its your duty to convince him to fix it.”,Attributes of a good tester,Curious, perceptive attentive to detail to comprehend the practic