Object-Oriented and Classical Software Engineering Eighth Edition, WCB/McGraw-Hill, 2011 Stephen R. Schach.

Object-Oriented and Classical Software Engineering Eighth Edition, WCB/McGraw-Hill, Stephen R. Schach

CHAPTER 6 TESTING

Overview Quality issues Non-execution-based testing
What should be tested? Testing versus correctness proofs Who should perform execution-based testing? When testing stops

Revise Terminology When humans make a MISTAKE, a FAULT is injected into the system FAILURE is the observed incorrect behavior of a product as a consequence of a FAULT. ERROR is the amount by which a result is incorrect DEFECT is a generic term for fault. QUALITY the extent to which a product satisfies its specifications.

ERROR IEEE Glossary of terms 610.12, 1990
(1) The difference between a computed, observed, or measured value or condition and the true, specified, or theoretically correct value or condition. For example, a difference of 30 meters between a computed result and the correct result. (2) An incorrect step, process, or data definition. For example, an incorrect instruction in a computer program.

FAULT MISTAKE FAILURE IEEE Glossary of terms 610.12, 1990
A defect in a hardware device or component; for example, a short circuit or broken MISTAKE A human action that produces an incorrect result. FAILURE The inability of a system or component to perform its required functions within specified performance requirements.

IEEE Glossary of terms , 1990 The fault tolerance discipline distinguishes between a human action (a mistake), its manifestation (a hardware or software fault), the result of the fault (a failure), and the amount by which the result is incorrect (the error).

Remember phases of Software Engineering

Phases of Classical Software Engineering
Requirements phase Explore the concept Elicit the client’s requirements Analysis (specification) phase Analyze the client’s requirements Draw up the specification document Draw up the software project management plan “What the product is supposed to do” Design phase Architectural design, followed by Detailed design “How the product does it” Implementation phase Coding Unit testing Integration Acceptance testing Postdelivery maintenance Corrective maintenance Perfective maintenance Adaptive maintenance Retirement

Testing There are two basic types of testing Execution-based testing
Non-execution-based testing

Program testing Testing is intended to show that a program does what it is intended to do and to discover program defects before it is put into use. When you test software, you execute a program using artificial data. You check the results of the test run for errors, anomalies or information about the program’s non-functional attributes. Can reveal the presence of errors NOT their absence. Testing is part of a more general verification and validation process, which also includes static validation techniques.

Program testing goals To demonstrate to the developer and the customer that the software meets its requirements. For custom software, this means that there should be at least one test for every requirement in the requirements document. For generic software products, it means that there should be tests for all of the system features, plus combinations of these features, that will be incorporated in the product release. To discover situations in which the behavior of the software is incorrect, undesirable or does not conform to its specification. Defect testing is concerned with rooting out undesirable system behavior such as system crashes, unwanted interactions with other systems, incorrect computations and data corruption.

Validation and defect testing
The first goal leads to validation testing You expect the system to perform correctly using a given set of test cases that reflect the system’s expected use. The second goal leads to defect testing The test cases are designed to expose defects. The test cases in defect testing can be deliberately obscure and need not reflect how the system is normally used.

Chapter 8 Software testing
Testing process goals Validation testing To demonstrate to the developer and the system customer that the software meets its requirements A successful test shows that the system operates as intended. Defect testing To discover faults or defects in the software where its behaviour is incorrect or not in conformance with its specification A successful test is a test that makes the system perform incorrectly and so exposes a defect in the system. Chapter 8 Software testing

An input-output model of program testing

Verification vs validation
Verification: "Are we building the product right”. The software should conform to its specification. Validation: "Are we building the right product”. The software should do what the user really requires.

V & V Revise Terminology Verification Validation
Process of determining whether a workflow has been correctly carried out Takes place at the end of each workflow Validation Intensive evaluation that determines if the product as a whole satisfies its requirements Takes place just before the product is to be delivered to the client

V & V confidence Aim of V & V is to establish confidence that the system is ‘fit for purpose’. Depends on system’s purpose, user expectations and marketing environment Software purpose The level of confidence depends on how critical the software is to an organisation. User expectations Users may have low expectations of certain kinds of software. Marketing environment Getting a product to market early may be more important than finding defects in the program. Chapter 8 Software testing

Inspections and testing
Software inspections Concerned with analysis of the static system representation to discover problems (static verification) May be supplemenedt by tool-based document and code analysis. Discussed in Chapter 15. Software testing Concerned with exercising and observing product behaviour (dynamic verification) The system is executed with test data and its operational behaviour is observed. Chapter 8 Software testing

Chapter 8 Software testing

Software inspections These involve people examining the source representation with the aim of discovering anomalies and defects. Inspections not require execution of a system so may be used before implementation. They may be applied to any representation of the system (requirements, design,configuration data, test data, etc.). They have been shown to be an effective technique for discovering program errors. Chapter 8 Software testing

Advantages of inspections
During testing, errors can mask (hide) other errors. Because inspection is a static process, you don’t have to be concerned with interactions between errors. Incomplete versions of a system can be inspected without additional costs. If a program is incomplete, then you need to develop specialized test harnesses to test the parts that are available. As well as searching for program defects, an inspection can also consider broader quality attributes of a program, such as compliance with standards, portability and maintainability. Chapter 8 Software testing

Inspections and testing are complementary and not opposing verification techniques. Both should be used during the V & V process. Inspections can check conformance with a specification but not conformance with the customer’s real requirements. Inspections cannot check non-functional characteristics such as performance, usability, etc. Chapter 8 Software testing

6.1 Software Quality Not “excellence”
The extent to which software satisfies its specifications Every software professional is responsible for ensuring that his or her work is correct Quality must be built in from the beginning

6.1.1 Software Quality Assurance
The members of the SQA group must ensure that the developers are doing high-quality work At the end of each workflow When the product is complete In addition, quality assurance must be applied to The process itself Example: Standards

Responsibilities of SQA Group
Development of standards to which software must conform Establishment of monitoring procedures for ensuring compliance with standards Ensure the quality of the software process Ensure the quality of the product

6.1.2 Managerial Independence
There must be managerial independence between The development team The SQA group Neither group should have power over the other 20 1 5 12 9 14 8 16 7 19 3 17 2 15 10 6 13 4 18 Problem: SQA team finds serious defects as the deadline approaches! What to do? Who decides?

Managerial Independence (contd)
More senior management must decide whether to Deliver the product on time but with faults, or Test further and deliver the product late The decision must take into account the interests of the client and the development organization

6.2 Non-Execution-Based Testing
Testing software without running test cases Reviewing software, carefully reading through it Analyzing software mathematically Underlying principles We should not review our own work Other people should do the review. We cannot see our own mistakes. Group synergy Review using a team of software professionals with a brad range of skills

Experienced Senior technical Staff members
Walkthroughs A walkthrough team consists of from four to six members It includes representatives of The team responsible for the current workflow The team responsible for the next workflow The SQA group The client representative The walkthrough is preceded by preparation Lists of items Items not understood Items that appear to be incorrect Experienced Senior technical Staff members

6.2.2 Managing Walkthroughs
The walkthrough team is chaired by the SQA representative In a walkthrough we detect faults, not correct them A correction produced by a committee is likely to be of low quality The cost of a committee correction is too high Not all items flagged are actually incorrect A walkthrough should not last longer than 2 hours There is no time to correct faults as well

Managing Walkthroughs (contd)
Walkthrough can be Participant driven : reviewers present their lists Document Driven : person/team responsible from the document walks through it A walkthrough must be document-driven, rather than participant-driven Walkthrough leader elicits questions and facilitates discussion Verbalization leads to fault finding A walkthrough should never be used for performance appraisal

6.2.3 Inspections An inspection has five formal steps
Overview : Given by a person responsible from producing the document Document distributed at the end of the session Preparation Understand the document in detail Use statistics of fault types Inspection One participant walks through the document Every item must be covered Every branch must be taken at least once Fault finding begins Within 1 day moderator (team leader) produces a written report Rework Person responsible resolves all faults and problems in the written document Follow-up Moderator ensures that all issues mentioned in the report are resolved List faults that were fixed. Clarify incorrectly flagged items

6.2.3 Inspections An inspection has five formal steps
Moderator ensures that all issues mentioned in the report are resolved List faults that were fixed. Clarify incorrectly flagged items Follow-up Person responsible resolves all faults and problems in the written document Rework One participant walks through the document Every item must be covered Every branch must be taken at least once Fault finding begins Within 1 day moderator (team leader) produces a written report Inspection Understand the document in detail Use statistics of fault types Preparation Given by a person responsible from producing the document Document distributed at the end of the session Overview :

Inspections (contd) An inspection team has four members
Moderator A member of the team performing the current workflow A member of the team performing the next workflow A member of the SQA group Special roles are played by the Reader Recorder

A fault that causes termination of the program
Fault Statistics A fault that causes termination of the program Faults are recorded by severity Example: Major or minor Faults are recorded by fault type Examples of design faults: Not all specification items have been addressed Actual and formal arguments do not correspond In general interface and logic errors

Fault Statistics (contd)
For a given workflow, we compare current fault rates with those of previous products Early warning!!!! If disproportionate number of a certain fault type is discovered in 203 code artifacts Check other artifacts for the same fault type We take action if there are a disproportionate number of faults in an artifact Redesigning from scratch is a good alternative We carry forward fault statistics to the next workflow We may not detect all faults of a particular type in the current inspection

Statistics on Inspections
IBM inspections showed up 82% of all detected faults (1976) 70% of all detected faults (1978) 93% of all detected faults (1986) Switching system 90% decrease in the cost of detecting faults (1986) JPL Four major faults, 14 minor faults per 2 hours (1990) Savings of $25,000 per inspection The number of faults decreased exponentially by phase (1992)

Statistics on Inspections (contd)
Warning Fault statistics should never be used for performance appraisal “Killing the goose that lays the golden eggs” Another problem:

6.2.4 Comparison of Inspections and Walkthroughs
Two-step, informal process Preparation Analysis Inspection Five-step, formal process Overview Rework Follow-up

6.2.5 Strengths and Weaknesses of Reviews
Reviews can be effective Faults are detected early in the process Reviews are less effective if the process is inadequate Large-scale software should consist of smaller, largely independent pieces The documentation of the previous workflows has to be complete and available online

6.2.6 Metrics for Inspections
Inspection rate (e.g., design pages inspected per hour) Fault density (e.g., faults per KLOC inspected) Fault detection rate (e.g., faults detected per hour) Fault detection efficiency (e.g., number of major, minor faults detected per hour)

Metrics for Inspections (contd)
Does a 50% increase in the fault detection rate mean that Quality has decreased? Or The inspection process is more efficient?

6.3 Execution-Based Testing
Organizations spend up to 50% of their software budget on testing But delivered software is frequently unreliable Dijkstra (1972) “Program testing can be a very effective way to show the presence of bugs, but it is hopelessly inadequate for showing their absence”

6.4 What Should Be Tested? Definition of execution-based testing
“The process of inferring certain behavioral properties of the product based, in part, on the results of executing the product in a known environment with selected inputs” This definition has troubling implications

6.4 What Should Be Tested? (contd)
“Inference” We have a fault report, the source code, and — often — nothing else Input data => Desirable output “Known environment” We never can really know our environment Is the problem due to memory? OS? “Selected inputs” Sometimes we cannot provide the inputs we want Simulation is needed Ex:” avionics software: how well can you simulate the phyical behavior outside the aircraft?

6.4 What Should Be Tested? (contd)
We need to test correctness (of course), and also Utility Reliability Robustness, and Performance

6.4.1 Utility The extent to which the product meets the user’s needs
Examples: Ease of use Useful functions Cost effectiveness Compare with competitors

Reliability A measure of the frequency and criticality of failure Mean time between failures Mean time to repair Time (and cost) to repair the results of a failure Recover gracefully and quickly

6.4.3 Robustness A function of
The range of operating conditions The possibility of unacceptable results with valid input The effect of invalid input A robust product should NOT crash when it is NOT used under valid conditions. Ex: enter as student id!

Performance The extent to which space and time constraints are met Response time, main mem requirements Real-time software is characterized by hard real-time constraints Nuclear reactor control system. If data are lost because the system is too slow There is no way to recover those data

Correctness A product is correct if it satisfies its output specifications, independent of it use of computer resources and when operated under permitted conditions

Correctness of specifications
Incorrect specification for a sort: Function trickSort which satisfies this specification: Figure 6.1 Figure 6.2

Correctness of specifications (contd)
Incorrect specification for a sort: Corrected specification for the sort: Figure 6.1 (again) Figure 6.3

Correctness (contd) Technically, correctness is Not necessary
Example: C++ compiler Not sufficient Example: trickSort

6.5 Testing versus Correctness Proofs
A correctness proof is an alternative to execution-based testing A correctness proof is a mathematical technique for showing that a product is correct Correct=satisfies it specification

6.5.1 Example of a Correctness Proof
The code segment to be proven correct Figure 6.4 Correct: After the code is executed the variable s will contain the sum of the n elements of the array y.

Example of a Correctness Proof (contd)
A flowchart equivalent of the code segment Figure 6.5

Input specification Output specification Loop invariant Assertions Add an assertion before an after each statement.

Figure 6.6

Three Myths of Correctness Proving
Software engineers do not have enough mathematics for proofs Most computer science majors either know or can learn the mathematics needed for proofs Proving is too expensive to be practical Economic viability is determined from cost–benefit analysis Proving is too hard Many nontrivial products have been successfully proven Tools like theorem provers can assist us

Difficulties with Correctness Proving
Can we trust a theorem prover ? Figure 6.7

Difficulties with Correctness Proving (contd)
How do we find input–output specifications, loop invariants? What if the specifications are wrong? We can never be sure that specifications or a verification system are correct

Correctness Proofs and Software Engineering (contd)
Correctness proofs are a vital software engineering tool, where appropriate: When human lives are at stake When indicated by cost–benefit analysis When the risk of not proving is too great Also, informal proofs can improve software quality Use the assert statement Model checking is a new technology that may eventually take the place of correctness proving (Section 18.11)

6.6 Who Should Perform Execution-Based Testing?
Programming is constructive Testing is destructive A successful test finds a fault So, programmers should not test their own code artifacts

Who Should Perform Execution-Based Testing? (contd)
Solution: The programmer does informal testing The SQA group then does systematic testing The programmer debugs the module All test cases must be Planned beforehand, including the expected output, and Retained afterwards

6.7 When Testing Stops Only when the product has been irrevocably discarded

Software Testing - objective
Execute a program to find errors A good test case has a high probability of finding errors A successful test finds a new error Software specs. Test Reports Results Testing Check Test specs.

A model of the software testing process

Stages of testing Development testing the system is tested during development to discover bugs and defects. Release testing a separate testing team test a complete version of the system before it is released to users. User testing users or potential users of a system test the system in their own environment. Chapter 8 Software testing

Development testing Unit testing Component testing System testing
Development testing includes all testing activities that are carried out by the team developing the system. Unit testing Component testing System testing individual program units or object classes are tested. several individual units are integrated to create composite components. some or all of the components in a system are integrated and the system is tested as a whole. should focus on testing the functionality of objects or methods. should focus on testing component interfaces. should focus on testing component interactions. Chapter 8 Software testing

Unit testing Unit testing is the process of testing individual components in isolation. It is a defect testing process. Units may be: Individual functions or methods within an object Object classes with several attributes and methods Composite components with defined interfaces used to access their functionality. Chapter 8 Software testing

Object class testing Complete test coverage of a class involves Testing all operations associated with an object Setting and interrogating all object attributes Exercising the object in all possible states. Inheritance makes it more difficult to design object class tests as the information to be tested is not localised. Chapter 8 Software testing

The weather station object interface

Weather station testing
Need to define test cases for reportWeather, calibrate, test, startup and shutdown. Using a state model, identify sequences of state transitions to be tested and the event sequences to cause these transitions For example: Shutdown -> Running-> Shutdown Configuring-> Running-> Testing -> Transmitting -> Running Running-> Collecting-> Running-> Summarizing -> Transmitting -> Running Chapter 8 Software testing

Automated testing Whenever possible, unit testing should be automated so that tests are run and checked without manual intervention. In automated unit testing, you make use of a test automation framework (such as JUnit) to write and run your program tests. Unit testing frameworks provide generic test classes that you extend to create specific test cases. They can then run all of the tests that you have implemented and report, often through some GUI, on the success or otherwise of the tests. Chapter 8 Software testing

Automated test components
A setup part, where you initialize the system with the test case, namely the inputs and expected outputs. A call part, where you call the object or method to be tested. An assertion part where you compare the result of the call with the expected result. If the assertion evaluates to true, the test has been successful if false, then it has failed. Chapter 8 Software testing

Unit test effectiveness
The test cases should show that, when used as expected, the component that you are testing does what it is supposed to do. If there are defects in the component, these should be revealed by test cases. This leads to 2 types of unit test case: The first of these should reflect normal operation of a program and should show that the component works as expected. The other kind of test case should be based on testing experience of where common problems arise. It should use abnormal inputs to check that these are properly processed and do not crash the component. Chapter 8 Software testing

Testing strategies Partition testing, where you identify groups of inputs that have common characteristics and should be processed in the same way. You should choose tests from within each of these groups. Guideline-based testing, where you use testing guidelines to choose test cases. These guidelines reflect previous experience of the kinds of errors that programmers often make when developing components. Chapter 8 Software testing

Partition testing Input data and output results often fall into different classes where all members of a class are related. Each of these classes is an equivalence partition or domain where the program behaves in an equivalent way for each class member. Test cases should be chosen from each partition. Chapter 8 Software testing

Equivalence partitioning

Equivalence partitions

Testing guidelines (sequences)
Test software with sequences which have only a single value. Use sequences of different sizes in different tests. Derive tests so that the first, middle and last elements of the sequence are accessed. Test with sequences of zero length. Chapter 8 Software testing

General testing guidelines
Choose inputs that force the system to generate all error messages Design inputs that cause input buffers to overflow Repeat the same input or series of inputs numerous times Force invalid outputs to be generated Force computation results to be too large or too small. Chapter 8 Software testing

Component testing Software components are often composite components that are made up of several interacting objects. For example, in the weather station system, the reconfiguration component includes objects that deal with each aspect of the reconfiguration. You access the functionality of these objects through the defined component interface. Testing composite components should therefore focus on showing that the component interface behaves according to its specification. You can assume that unit tests on the individual objects within the component have been completed. Chapter 8 Software testing

Interface testing Chapter 8 Software testing

Interface testing Objectives are to detect faults due to interface errors or invalid assumptions about interfaces. Interface types Parameter interfaces Data passed from one method or procedure to another. Shared memory interfaces Block of memory is shared between procedures or functions. Procedural interfaces Sub-system encapsulates a set of procedures to be called by other sub-systems. Message passing interfaces Sub-systems request services from other sub-systems Chapter 8 Software testing

Interface errors Interface misuse A calling component calls another component and makes an error in its use of its interface e.g. parameters in the wrong order. Interface misunderstanding A calling component embeds assumptions about the behaviour of the called component which are incorrect. Timing errors The called and the calling component operate at different speeds and out-of-date information is accessed. Chapter 8 Software testing

Interface testing guidelines
Design tests so that parameters to a called procedure are at the extreme ends of their ranges. Always test pointer parameters with null pointers. Design tests which cause the component to fail. Use stress testing in message passing systems. In shared memory systems, vary the order in which components are activated. Chapter 8 Software testing

System testing System testing during development involves integrating components to create a version of the system and then testing the integrated system. The focus in system testing is testing the interactions between components. System testing checks that components are compatible, interact correctly and transfer the right data at the right time across their interfaces. System testing tests the emergent behaviour of a system. Chapter 8 Software testing

System and component testing
During system testing, reusable components that have been separately developed and off-the-shelf systems may be integrated with newly developed components. The complete system is then tested. Components developed by different team members or sub-teams may be integrated at this stage. System testing is a collective rather than an individual process. In some companies, system testing may involve a separate testing team with no involvement from designers and programmers. Chapter 8 Software testing

Use-case testing The use-cases developed to identify system interactions can be used as a basis for system testing. Each use case usually involves several system components so testing the use case forces these interactions to occur. The sequence diagrams associated with the use case documents the components and interactions that are being tested. Chapter 8 Software testing

Collect weather data sequence chart

Testing policies Exhaustive system testing is impossible so testing policies which define the required system test coverage may be developed. Examples of testing policies: All system functions that are accessed through menus should be tested. Combinations of functions (e.g. text formatting) that are accessed through the same menu must be tested. Where user input is provided, all functions must be tested with both correct and incorrect input. Chapter 8 Software testing

Test-driven development
Test-driven development (TDD) is an approach to program development in which you inter-leave testing and code development. Tests are written before code and ‘passing’ the tests is the critical driver of development. You develop code incrementally, along with a test for that increment. You don’t move on to the next increment until the code that you have developed passes its test. TDD was introduced as part of agile methods such as Extreme Programming. However, it can also be used in plan-driven development processes. Chapter 8 Software testing

Test-driven development

TDD process activities
Start by identifying the increment of functionality that is required. This should normally be small and implementable in a few lines of code. Write a test for this functionality and implement this as an automated test. Run the test, along with all other tests that have been implemented. Initially, you have not implemented the functionality so the new test will fail. Implement the functionality and re-run the test. Once all tests run successfully, you move on to implementing the next chunk of functionality. Chapter 8 Software testing

Benefits of test-driven development
Code coverage Every code segment that you write has at least one associated test so all code written has at least one test. Regression testing A regression test suite is developed incrementally as a program is developed. Simplified debugging When a test fails, it should be obvious where the problem lies. The newly written code needs to be checked and modified. System documentation The tests themselves are a form of documentation that describe what the code should be doing. Chapter 8 Software testing

Regression testing Regression testing is testing the system to check that changes have not ‘broken’ previously working code. In a manual testing process, regression testing is expensive but, with automated testing, it is simple and straightforward. All tests are rerun every time a change is made to the program. Tests must run ‘successfully’ before the change is committed. Chapter 8 Software testing

Release testing Release testing is the process of testing a particular release of a system that is intended for use outside of the development team. The primary goal of the release testing process is to convince the supplier of the system that it is good enough for use. Release testing, therefore, has to show that the system delivers its specified functionality, performance and dependability, and that it does not fail during normal use. Release testing is usually a black-box testing process where tests are only derived from the system specification. Chapter 8 Software testing

Release testing and system testing
Release testing is a form of system testing. Important differences: A separate team that has not been involved in the system development, should be responsible for release testing. System testing by the development team should focus on discovering bugs in the system (defect testing). The objective of release testing is to check that the system meets its requirements and is good enough for external use (validation testing). Chapter 8 Software testing

Requirements based testing
Requirements-based testing involves examining each requirement and developing a test or tests for it. MHC-PMS requirements: If a patient is known to be allergic to any particular medication, then prescription of that medication shall result in a warning message being issued to the system user. If a prescriber chooses to ignore an allergy warning, they shall provide a reason why this has been ignored. Chapter 8 Software testing

Requirements tests Set up a patient record with no known allergies. Prescribe medication for allergies that are known to exist. Check that a warning message is not issued by the system. Set up a patient record with a known allergy. Prescribe the medication to that the patient is allergic to, and check that the warning is issued by the system. Set up a patient record in which allergies to two or more drugs are recorded. Prescribe both of these drugs separately and check that the correct warning for each drug is issued. Prescribe two drugs that the patient is allergic to. Check that two warnings are correctly issued. Prescribe a drug that issues a warning and overrule that warning. Check that the system requires the user to provide information explaining why the warning was overruled. Chapter 8 Software testing

Features tested by scenario
Authentication by logging on to the system. Downloading and uploading of specified patient records to a laptop. Home visit scheduling. Encryption and decryption of patient records on a mobile device. Record retrieval and modification. Links with the drugs database that maintains side-effect information. The system for call prompting. Chapter 8 Software testing

A usage scenario for the MHC-PMS
Kate is a nurse who specializes in mental health care. One of her responsibilities is to visit patients at home to check that their treatment is effective and that they are not suffering from medication side -effects. On a day for home visits, Kate logs into the MHC-PMS and uses it to print her schedule of home visits for that day, along with summary information about the patients to be visited. She requests that the records for these patients be downloaded to her laptop. She is prompted for her key phrase to encrypt the records on the laptop. One of the patients that she visits is Jim, who is being treated with medication for depression. Jim feels that the medication is helping him but believes that it has the side -effect of keeping him awake at night. Kate looks up Jim’s record and is prompted for her key phrase to decrypt the record. She checks the drug prescribed and queries its side effects. Sleeplessness is a known side effect so she notes the problem in Jim’s record and suggests that he visits the clinic to have his medication changed. He agrees so Kate enters a prompt to call him when she gets back to the clinic to make an appointment with a physician. She ends the consultation and the system re-encrypts Jim’s record. After, finishing her consultations, Kate returns to the clinic and uploads the records of patients visited to the database. The system generates a call list for Kate of those patients who she has to contact for follow-up information and make clinic appointments. Chapter 8 Software testing

Performance testing Part of release testing may involve testing the emergent properties of a system, such as performance and reliability. Tests should reflect the profile of use of the system. Performance tests usually involve planning a series of tests where the load is steadily increased until the system performance becomes unacceptable. Stress testing is a form of performance testing where the system is deliberately overloaded to test its failure behaviour. Chapter 8 Software testing

User testing User or customer testing is a stage in the testing process in which users or customers provide input and advice on system testing. User testing is essential, even when comprehensive system and release testing have been carried out. The reason for this is that influences from the user’s working environment have a major effect on the reliability, performance, usability and robustness of a system. These cannot be replicated in a testing environment. Chapter 8 Software testing

Types of user testing Alpha testing Users of the software work with the development team to test the software at the developer’s site. Beta testing A release of the software is made available to users to allow them to experiment and to raise problems that they discover with the system developers. Acceptance testing Customers test a system to decide whether or not it is ready to be accepted from the system developers and deployed in the customer environment. Primarily for custom systems. Chapter 8 Software testing

The acceptance testing process

Stages in the acceptance testing process
Define acceptance criteria Plan acceptance testing Derive acceptance tests Run acceptance tests Negotiate test results Reject/accept system Chapter 8 Software testing

Agile methods and acceptance testing
In agile methods, the user/customer is part of the development team and is responsible for making decisions on the acceptability of the system. Tests are defined by the user/customer and are integrated with other tests in that they are run automatically when changes are made. There is no separate acceptance testing process. Main problem here is whether or not the embedded user is ‘typical’ and can represent the interests of all system stakeholders. Chapter 8 Software testing

There are two main types of Software Testing
Black Box White Box

Black Box Black box testing . . . You know the functionality
Given that you know what it is supposed to do, you design tests that make it do what you think that it should do From the outside, you are testing its functionality against the specs/requirements For software this is testing the interface What is input to the system? What you can do from the outside to change the system? What is output from the system? Tests the functionality of the system by observing its external behavior No knowledge of how it goes about meeting the goals

White Box White box testing . . . You know the code
Given knowledge of the internal workings, you thoroughly test what is happening on the inside Close examination of procedural level of detail Logical paths through code are tested Conditionals Loops Branches Status is examined in terms of expected values Impossible to thoroughly exercise all paths Exhaustive testing grows without bound Can be practical if a limited number of “important” paths are evaluated Can be practical to examine and test important data structures

When & What to Test? Low Level of Detail High Requirements Acceptance
Specifications Acceptance Testing Low System Testing Analysis Level of Detail The V-model is a variation of the waterfall model that makes explicit the dependency between development activities and verification activities. The difference between the waterfall model and the V model is that the latter makes explicit the notion of level of abstraction. Allactivities from requirements to implementation focus on building more and more detailed representation of the system, whereas all activities from implementation to operation focus on validating the system. Design Integration Testing Object Design Unit Testing High Project Time

Types of Testing Unit Testing Integration/Component Testing
Done by programmer(s) Generally all white box Integration/Component Testing Done by programmer as they integrate their code into code base Generally white box, maybe some black box Functional/System Testing It is recommended that this be done by an external test group Mostly black box so that testing is not ‘corrupted’ by too much knowledge Acceptance Testing Generally done by customer/customer representative in their environment through the GUI Definitely black box

The Testing Process

Planning a Black Box Test Case
Look at requirements/problem statement to generate. Said another way: test cases should be traceable to requirements. The “Test Case Grid” Contains: ID of test case Describe test input conditions Expected/Predicted results Actual Results

Test Case Grid Id Input Expected Result Actual Result
For your analysis reports, please use the following format: Id Input Expected Result Actual Result

Black Box Test Planning
The inputs must be very specific The expected results must be very specific You must write the test case so anyone on the team can run the exact test case and get the exact same result/sequence of events Example: “Passing grade?” Input field: Correct input: Grade = 90; Grade =20 Incorrect input: “a passing grade” “a failing grade”

Example Test Case Grid Id Input Expected Result Actual Result
Your test case grid (last section of your analysis document) should identify at least 15 test cases. Example: “Passing grade?” Id Input Expected Result Actual Result 1 Grade < 70% Fail the class with less than a C (Leave blank until tested) 2 Grade > 70% Pass the class with at least a C

Bad Test Case Example Id Input Expected Result Actual Result
A failing grade 1 Fail the class with less than a C (Leave blank until tested) A passing grade 2 Pass the class with at least a C What is a failing and passing grade? Problem: The “input” value is too vague.

Failure Test Cases What if the input type is wrong (You’re expecting an integer, they input a float. You’re expecting a character, you get an integer.)? What if the customer takes an illogical path through your functionality? What if mandatory fields are not entered? What if the program is aborted abruptly or input or output devices are unplugged?

Using a Flow Chart if x >= 0 Key if x <=100 check= false
Decision if x <=100 statements check= false Mapping functionality in a flow chart makes the test case generation process much easier. check= true

One input leads to One output
A piece of code with inputs a, b, and c. It produces the outputs x, y, and z.

One-to-One Testing Each input only has one valid expected result.
To check for a valid ATM Card the following is NOT correct. Id Input Expected Result Actual Result 1 Read ATM Card If card is valid, accept card and ask for pin. If card is invalid, “No ATM Card” exception is thrown and card is returned to the user.

The correct way… Id Input Expected Result Actual Result
Test for ATM card Input: Read ATM Card Expected result: Accept card and ask for pin # Input: Read invalid card Expected result: “No ATM Card” exception is thrown and card is returned to the user. Id Input Expected Result Actual Result 1 Read ATM Card Accept card and ask for pin # 2 Read Invalid Card “No ATM Card” exception is thrown and card is returned to the user.

Another test… Id Input Expected Result Actual Result
Test for “get PIN” Input: 4 digit entry of a stolen card Expected result: “Stolen Card” exception is thrown Id Input Expected Result Actual Result 1 Read ATM Card Accept card and ask for pin # Read Invalid Card “No ATM Card” exception is thrown and card is returned to the user. 2 Invalid PIN Entered “Stolen Card” exception is thrown and card is destroyed. 3

What’s Next? After tests are performed, the results are recorded.
Id Input Expected Result Actual Result 1 Read ATM Card Accept card and ask for pin # Accepted the card and asked for a pin. Read Invalid Card “No ATM Card” exception is thrown and card is returned to the user. 2 Accepted the card and asked for a pin. Invalid PIN Entered Accepted the card and asked for a pin. “Stolen Card” exception is thrown and card is destroyed. 3

What’s Next? After results are recorded, the testing report is created. Id Input Expected Result Actual Result Status 1 Read ATM Card Accept card and ask for pin # Accepted the card and asked for a pin. Passed Read Invalid Card “No ATM Card” exception is thrown and card is returned to the user. 2 Accepted the card and asked for a pin. Failed Invalid PIN Entered “Stolen Card” exception is thrown and card is destroyed. Accepted the card and asked for a pin. 3 Failed

Verification & Validation
Testing is performed during the system implementation stage and the results are delivered in the Final Report. The Test Report provides validation and verification for the software program. Verification: "Are we building the product right?" The software should conform to its specification Validation: "Are we building the right product?" The software should do what the user really requires

Project Work Your Analysis Document is due soon! Next:
Begin discussion of the Design Specification Requirements Review and prepare for the midterm exam Midterm Exam, coming soon!

Object-Oriented and Classical Software Engineering Eighth Edition, WCB/McGraw-Hill, 2011 Stephen R. Schach.

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Object-Oriented and Classical Software Engineering Eighth Edition, WCB/McGraw-Hill, 2011 Stephen R. Schach.

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Presentation on theme: "Object-Oriented and Classical Software Engineering Eighth Edition, WCB/McGraw-Hill, 2011 Stephen R. Schach."— Presentation transcript:

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