Test Double
Encyclopedia
In computer programming
and computer science
, especially in object-oriented programming
, programmers
and developers
employ a technique called, "automated unit testing" to enhance the quality of the software. Frequently, the final release software consists of a complex set of objects
or procedures
interacting together to create the final result. In Automated unit testing, it may be necessary to use objects or procedures that look and behave like their release-intended counterparts, but are actually simplified versions that reduce the complexity and facilitate testing. A test double is a generic (meta) term used for these objects or procedures.
While there is no open standard
for test double and the various types, there is momentum for continued use of these terms in this manner. Martin Fowler
used these terms in his article, Mocks Aren't Stubs referring to Meszaros' book. Microsoft also used the same terms and definitions in an article titled, Exploring The Continuum Of Test Doubles.
Computer programming
Computer programming is the process of designing, writing, testing, debugging, and maintaining the source code of computer programs. This source code is written in one or more programming languages. The purpose of programming is to create a program that performs specific operations or exhibits a...
and computer science
Computer science
Computer science or computing science is the study of the theoretical foundations of information and computation and of practical techniques for their implementation and application in computer systems...
, especially in object-oriented programming
Object-oriented programming
Object-oriented programming is a programming paradigm using "objects" – data structures consisting of data fields and methods together with their interactions – to design applications and computer programs. Programming techniques may include features such as data abstraction,...
, programmers
Programmer
A programmer, computer programmer or coder is someone who writes computer software. The term computer programmer can refer to a specialist in one area of computer programming or to a generalist who writes code for many kinds of software. One who practices or professes a formal approach to...
and developers
Software developer
A software developer is a person concerned with facets of the software development process. Their work includes researching, designing, developing, and testing software. A software developer may take part in design, computer programming, or software project management...
employ a technique called, "automated unit testing" to enhance the quality of the software. Frequently, the final release software consists of a complex set of objects
Object (computer science)
In computer science, an object is any entity that can be manipulated by the commands of a programming language, such as a value, variable, function, or data structure...
or procedures
Subroutine
In computer science, a subroutine is a portion of code within a larger program that performs a specific task and is relatively independent of the remaining code....
interacting together to create the final result. In Automated unit testing, it may be necessary to use objects or procedures that look and behave like their release-intended counterparts, but are actually simplified versions that reduce the complexity and facilitate testing. A test double is a generic (meta) term used for these objects or procedures.
Types of test doubles
Gerard Meszaros identified several different terms for what he calls, "Test Doubles." Using his vocabulary, there are at least five types of Test Doubles:- Test stubTest stubsIn computer science, test stubs are programs which simulate the behaviors of software components that are the dependent modules of the module being tested.Test Stubs are mainly used in incremental testing's Top-Down approach...
(used for providing the tested code with "indirect input") - Mock objectMock objectIn object-oriented programming, mock objects are simulated objects that mimic the behavior of real objects in controlled ways. A programmer typically creates a mock object to test the behavior of some other object, in much the same way that a car designer uses a crash test dummy to simulate the...
(used for verifying "indirect output" of the tested code, by first defining the expectations before the tested code is executed) - Test spy (used for verifying "indirect output" of the tested code, by asserting the expectations afterwards, without having defined the expectations before the tested code is executed)
- Fake object (used as a simpler implementation, e.g. using an in-memory database in the tests instead of doing real database access)
- Dummy object (used when a parameter is needed for the tested method but without actually needing to use the parameter)
While there is no open standard
Open standard
An open standard is a standard that is publicly available and has various rights to use associated with it, and may also have various properties of how it was designed . There is no single definition and interpretations vary with usage....
for test double and the various types, there is momentum for continued use of these terms in this manner. Martin Fowler
Martin Fowler
-Online presentations:* at RailsConf 2006* at JAOO 2006* at QCon London 2007 * at QCon London 2008 * at ThoughtWorks Quarterly Technology Briefing, October 2008...
used these terms in his article, Mocks Aren't Stubs referring to Meszaros' book. Microsoft also used the same terms and definitions in an article titled, Exploring The Continuum Of Test Doubles.