Cap8 Software Testing Flashcards
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.
The first goal leads to validation testing
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.
The second goal leads to defect testing
Validation and defect testing
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.
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 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.
Inspections and testing
Software inspections Concerned with analysis of the static system representation to discover problems (static verification)
May be supplement by tool-based document and code analysis.
Software testing Concerned with exercising and observing product behaviour (dynamic verification)
The system is executed with test data and its operational behaviour is observed.
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.
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.
Inspections and 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.
Development testing
Development testing includes all testing activities that are carried out by the team developing the system.
Unit testing, where individual program units or object classes are tested. Unit testing should focus on testing the functionality of objects or methods.
Component testing, where several individual units are integrated to create composite components. Component testing should focus on testing component interfaces.
System testing, where some or all of the components in a system are integrated and the system is tested as a whole. System testing should focus on testing component interactions.
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.
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.
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 of otherwise of the tests.
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.
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.
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.
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.
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.
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.
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
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.
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.
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.
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
