测试概论第四次课

1 error may lead to many faults A failure may occur a "long way" from the original fault One fault may lead to many failures
缺陷 Faults与 Failures失效 与 失效
四类常见接口
File System Interfaces These exist when software reads or writes data to external files. Developers must write lots of errorchecking code to determine if the file contains the appropriate data and formatting. Tester must generate files with content that is both legal and illegal, and files that contain a variety of formatting Communication Interfaces These allow direct access to physical devices and require a communication protocol. Testers must generate valid and invalid protocol streams. Testers must also assemble many different combinations of commands and data in the proper packet format
Throughput or performance faults This is when the developed system does not perform at the speed specified under the stipulated（规定的） requirements Recovery faults This happens when the system does not recover to the expected performance even after a fault is detected and corrected
Documentation faults
软件缺陷分类
Incomplete or incorrect documentation will lead to Documentation faults Stress or overload faults Stress or Overload faults happens when data structures are filled past their specific capacity where as the system characteristics are designed to handle no more than a maximum load planned under the requirements
测试人员的任务
The tester must simulate interaction between the software and its environment They must identify and simulate the interfaces that a software system uses and enumerate the inputs that can cross each interface
用户意外操作
Testers must also consider other types of user interaction that fall outside the control of the software under test. Examples are: Using the OS, if one user deletes a file that another has open what happens the next time the software tries to access that file? A device is rebooted in the middle of a stream of communication. Will the software realise this and react properly or just hang? Two software systems compete for duplicate services from an API. Will the API correctly service both?
软件测试的目标
Testing is all about finding faults Testing assists in bringing the software to an acceptable level of quality Testing helps to determine the risk of release
Debugging is the process of locating and removing faults in software
几个术语
? TEST
ERROR
? FAULT DEBUG
? FAILURE
bugs, Errors, Faults and Failures
The term “bug” is not very precise Software Testers do not "fix bugs"! An ERROR is a human action that produces an incorrect result Errors result in FAULTS in the software Faults may result in FAILURES when the software runs:
验证Verification与 确认Validation
• Verification : have we built the system correctly？ • Validation: have we built the correct system？ • Programmers perspective: take the specifications as a reference point; ensure its testability • Users perspective: software is erroneous if it doesn't match expectations; review specification
软件缺陷分类
Algorithmic faults Algorithmic faults are the one that occurs when a unit of the software does not produce an output corresponding to the given input under the designated algorithm Syntax Faults Syntax faults are due to the nonconformity of programming language
软件缺陷分类
Capacity and boundary faults Capacity or Boundary faults occur when the system produces an unacceptable performance because the system activity may reach its specified limit due to overload
四类常见接口
Human Interfaces The most common interface here is the GUI, but older designs use the command line interface or the menudriven interface. Input mechanisms include mouse clicks and keyboard events. Testers must organise this data into an effective test Software Interfaces These are APIs and determine how a piece of software uses an OS, a database or runtime library. The services these applications provide can be modelled as test inputs. The testers must check expected and unexpected services. For example, what is a file save mechanism indicate when the disk is full?
与测试相关的活动
Tool-based static code analysis (e.g. for Security assessment, Human documentation/code scrutiny Debugging: NB: Testing is NOT debugging, and debugging ition and precision faults Computation and Precision faults occur when the calculated result using the chosen formula does not confirm to the expected accuracy or precision