Test double

Last updated

A test double is software used in software test automation that satisfies a dependency so that the test need not depend on production code. A test double provides functionality via an interface that the software under test cannot distinguish from production code.

Contents

A programmer generally uses a test double to isolate the behavior of the consuming code from the rest of the codebase.

A test double is usually a simplified version of the production code and may include capabilities specific to testing.

Test doubles are used to build test harnesses.

Uses

A test double may be used to simplify and speed test execution.

For example, a program that uses a database server is relatively slow and consumes significant system resources – which impedes testing productivity. Also, a test case might require values outside those stored in the database. A test double might provide a static value instead of accessing a database.

A test double may be used to test part of the system that is ready for testing even if its dependencies are not.

For example, in a system with modules Login, Home and User, suppose Login is ready for test, but the other two are not. The consumed functions of Home and User can be implemented as test doubles so that Login can be tested.

Types

Test doubles are categorization many ways.

General

Although not universally accepted, Gerard Meszaros [1] categorizes test doubles as:

While there is no open standard for categories, Martin Fowler used these terms in his article, Mocks Aren't Stubs [2] referring to Meszaros' book. Microsoft also used the same terms and definitions in an article titled, Exploring The Continuum Of Test Doubles. [3]

Service

For service-oriented architecture (SOA) systems and microservices, testers use test doubles that communicate with the system under test over a network protocol. [4] [5] These test doubles are called by different names by the tool vendors. A commonly used term is service virtualization. Other names used include API simulation, API mock, [6] HTTP stub, HTTP mock, over the wire test double [7] . [8]

Verified fake

A verified fake is a fake object whose behavior has been verified to match that of the real object using a set of tests that run against both the verified fake and the real implementation. [9]

See also

Related Research Articles

JUnit is a test automation framework for the Java programming language. JUnit is often used for unit testing, and is one of the xUnit frameworks.

Unit testing, a.k.a. component or module testing, is a form of software testing by which isolated source code is tested to validate expected behavior.

xUnit is a label used for an automated testing software framework that shares significant structure and functionality that is traceable to a common progenitor SUnit.

Test-driven development (TDD) is a way of writing code that involves writing an automated unit-level test case that fails, then writing just enough code to make the test pass, then refactoring both the test code and the production code, then repeating with another new test case.

Web development is the work involved in developing a website for the Internet or an intranet. Web development can range from developing a simple single static page of plain text to complex web applications, electronic businesses, and social network services. A more comprehensive list of tasks to which Web development commonly refers, may include Web engineering, Web design, Web content development, client liaison, client-side/server-side scripting, Web server and network security configuration, and e-commerce development.

In software engineering, service-oriented architecture (SOA) is an architectural style that focuses on discrete services instead of a monolithic design. SOA is a good choice for system integration. By consequence, it is also applied in the field of software design where services are provided to the other components by application components, through a communication protocol over a network. A service is a discrete unit of functionality that can be accessed remotely and acted upon and updated independently, such as retrieving a credit card statement online. SOA is also intended to be independent of vendors, products and technologies.

A method stub is a short and simple placeholder for a method that is not yet written for production needs. Generally, a method stub contains just enough code to allow it to be used – a declaration with any parameters, and if applicable, a return value.

In software testing, test automation is the use of software separate from the software being tested to control the execution of tests and the comparison of actual outcomes with predicted outcomes. Test automation can automate some repetitive but necessary tasks in a formalized testing process already in place, or perform additional testing that would be difficult to do manually. Test automation is critical for continuous delivery and continuous testing.

In computer science, a mock object is an object that imitates a production object in limited ways. A programmer might use a mock object as a test double for software testing. A mock object can also be used in generic programming.

<span class="mw-page-title-main">Mockup</span> Scale or full-size model of a design or device

In manufacturing and design, a mockup, or mock-up, is a scale or full-size model of a design or device, used for teaching, demonstration, design evaluation, promotion, and other purposes. A mockup may be a prototype if it provides at least part of the functionality of a system and enables testing of a design.

In distributed computing, a stub is a program that acts as a temporary replacement for a remote service or object. It allows the client application to access a service as if it were local, while hiding the details of the underlying network communication. This can simplify the development process, as the client application does not need to be aware of the complexities of distributed computing. Instead, it can rely on the stub to handle the remote communication, while providing a familiar interface for the developer to work with.

A test stub is a test double that provides static values to the software under test.

Parasoft SOAtest is a testing and analysis tool suite for testing and validating APIs and API-driven applications. Basic testing functionality include functional unit testing, integration testing, regression testing, system testing, security testing, simulation and mocking, runtime error detection, web UI testing, interoperability testing, WS-* compliance testing, and load testing.

In software engineering, service virtualization or service virtualisation is a method to emulate the behavior of specific components in heterogeneous component-based applications such as API-driven applications, cloud-based applications and service-oriented architectures. It is used to provide software development and QA/testing teams access to dependent system components that are needed to exercise an application under test (AUT), but are unavailable or difficult-to-access for development and testing purposes. With the behavior of the dependent components "virtualized", testing and development can proceed without accessing the actual live components. Service virtualization is recognized by vendors, industry analysts, and industry publications as being different than mocking. See here for a Comparison of API simulation tools.

In software engineering, a microservice architecture is an architectural pattern that arranges an application as a collection of loosely coupled, fine-grained services, communicating through lightweight protocols. A microservice-based architecture enables teams to develop and deploy their services independently, reduce code interdependency and increase readability and modularity within a codebase. This is achieved by reducing several dependencies in the codebase, allowing developers to evolve their services with limited restrictions, and reducing additional complexity. Consequently, organizations can develop software with rapid growth and scalability, as well as implement off-the-shelf services more easily. These benefits come with the cost of needing to maintain a decoupled structure within the codebase, which means its initial implementation is more complex than that of a monolithic codebase. Interfaces need to be designed carefully and treated as APIs.

Wilma is a Service virtualization software tool that computer programmers and testers use for developing and testing other software. It sits between software components, software services, microservices, as a transparent proxy, and captures the communication traffic between the software components. Based on its actual configuration, evaluates the captured messages and decides between proxying the request or providing response by itself, as a service stub. Therefore, it is a combined Transparent Proxy and Service Stub. It is written in Java, and Open Sourced under the license GPL.

Bogus is a Ruby API library used for minimizing risks involved in isolated unit testing. It was initially released in July 2012 by rubygems.org. Through Bogus, a piece of code can be tested in a fast and safe manner, without any actual integration with external programs. Bogus cannot mock or stub methods not present in the required external environment.

The tools listed here support emulating or simulating APIs and software systems. They are also called API mocking tools, service virtualization tools, over the wire test doubles and tools for stubbing and mocking HTTP(S) and other protocols. They enable component testing in isolation.

The hexagonal architecture, or ports and adapters architecture, is an architectural pattern used in software design. It aims at creating loosely coupled application components that can be easily connected to their software environment by means of ports and adapters. This makes components exchangeable at any level and facilitates test automation.

Quarkus is a Java framework tailored for deployment on Kubernetes. Key technology components surrounding it are OpenJDK HotSpot and GraalVM. Quarkus aims to make Java a leading platform in Kubernetes and serverless environments while offering developers a unified reactive and imperative programming model to address a wider range of distributed application architectures optimally.

References

  1. ↑ Meszaros, Gerard (2007). xUnit Test Patterns: Refactoring Test Code. Addison-Wesley. ISBN   978-0-13-149505-0.
  2. ↑ Fowler, Martin (2007). "Mocks Aren't Stubs" . Retrieved 2010-12-29.
  3. ↑ Seemann, Mark (2007). "Exploring The Continuum Of Test Doubles" . Retrieved 2010-12-29.
  4. ↑ Clemson, Toby "Testing Strategies in a Microservice Architecture", martinfowler.com, 18 November 2014. Retrieved on 07 December 2017.
  5. ↑ Byars, Brandon. "Testing Microservices with Mountebank", Manning Publications , MEAP began March 2017. ISBN   9781617294778. Retrieved on 07 December 2017.
  6. ↑ Bryant, Daniel "API Mocking Tool WireMock v2 Released with Improved Request Matching and Stub Management", InfoQ , 16 August 2016. Retrieved on 07 December 2017.
  7. ↑ ThoughtWorks "Technology Radar, Tools: Mountebank", ThoughtWorks , November 2015. Retrieved on 07 December 2017.
  8. ↑ Bulaty, Wojciech "Stubbing, Mocking and Service Virtualization Differences for Test and Development Teams", InfoQ , 19 February 2016. Retrieved on 07 December 2017.
  9. ↑ Turner-Trauring, Itamar (2019). "Fast tests for slow services: why you should use verified fakes" . Retrieved 2019-01-21.

Gerard Meszaros:

Martin Fowler:

Open source:

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.