What s the difference between unit functional acceptance and integration tests

Question

What is the difference between unit  functional  acceptance  and integration testing  and any other types of tests that I failed to mention

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Some  relatively  recent ideas against excessive mocking and pure unit-testing    https   www simple-talk com dotnet  net-framework are-unit-tests-overused  http   googletesting blogspot com 2013 05 testing-on-toilet-dont-overuse-mocks html http   codebetter com iancooper 2011 10 06 avoid-testing-implementation-details-test-behaviours  http   cdunn2001 blogspot com 2014 04 the-evil-unit-test html http   www jacopretorius net 2012 01 test-behavior-not-implementation html Why Most Unit Testing is Waste

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Unit Testing - As the name suggests  this method tests at the object level  Individual software components are tested for any errors  Knowledge of the program is needed for this test and the test codes are created to check if the software behaves as it is intended to   Functional Testing - Is carried out without any knowledge of the internal working of the system  The tester will try to use the system by just following requirements  by providing different inputs and testing the generated outputs  This test is also known as closed-box testing or black-box   Acceptance Testing - This is the last test that is conducted before the software is handed over to the client  It is carried out to ensure that the developed software meets all the customer requirements  There are two types of acceptance testing - one that is carried out by the members of the development team  known as internal acceptance testing  Alpha testing   and the other that is carried out by the customer or end user known as  Beta testing     Integration Testing - Individual modules that are already subjected to unit testing are integrated with one another  Generally the two approachs are followed    1  Top-Down 2  Bottom-Up

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The important thing is that you know what those terms mean to your colleagues   Different groups will have slightly varying definitions of what they mean when they say  full end-to-end  tests  for instance    I came across Google s naming system for their tests recently  and I rather like it - they bypass the arguments by just using Small  Medium  and Large   For deciding which category a test fits into  they look at a few factors - how long does it take to run  does it access the network  database  filesystem  external systems and so on   http   googletesting blogspot com 2010 12 test-sizes html  I d imagine the difference between Small  Medium  and Large for your current workplace might vary from Google s     However  it s not just about scope  but about purpose   Mark s point about differing perspectives for tests  e g  programmer vs customer end user  is really important

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http   martinfowler com articles microservice-testing   Martin Fowler s blog post speaks about strategies to test code  Especially in a micro-services architecture  but most of it applies to any application   I ll quote from his summary slide         Unit tests - exercise the smallest pieces of testable software in the application to determine whether they behave as expected    Integration tests - verify the communication paths and interactions between components to detect interface defects    Component tests - limit the scope of the exercised software to a portion of the system under test  manipulating the system through   internal code interfaces and using test doubles to isolate the code   under test from other components    Contract tests - verify interactions at the boundary of an external service asserting that it meets the contract expected by a consuming   service    End-To-End tests -  verify that a system meets external requirements and achieves its goals  testing the entire system  from   end to end

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unit test  testing of individual module or independent component in an application is known to be unit testing   the unit testing will be done by developer   integration test  combining all the modules and testing the application to verify the communication and the data flow between the modules are working properly or not   this testing also performed by developers   funcional test checking the individual functionality of an application is mean to be functional testing  acceptance testing this testing is done by end user or customer whether the build application is according to the customer requirement   and customer specification this is known to be acceptance testing

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I will explain you this with a practical example and no theory stuff   A developer writes the code  No GUI is implemented yet  The testing at this level verifies that the functions work correctly and the data types are correct  This phase of testing is called Unit testing   When a GUI is developed  and application is assigned to a tester  he verifies business requirements with a client and executes the different scenarios  This is called functional testing  Here we are mapping the client requirements with application flows   Integration testing  let s say our application has two modules  HR and Finance  HR module was delivered and tested previously  Now Finance is developed and is available to test  The interdependent features are also available now  so in this phase  you will test communication points between the two and will verify they are working as requested in requirements   Regression testing is another important phase  which is done after any new development or bug fixes  Its aim is to verify previously working functions

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This is very simple    Unit testing  This is the testing actually done by developers that have coding knowledge  This testing is done at the coding phase and it is a part of white box testing  When a software comes for development  it is developed into the piece of code or slices of code known as a unit  And individual testing of these units called unit testing done by developers to find out some kind of human mistakes like missing of statement coverage etc   Functional testing  This testing is done at testing  QA  phase and it is a part of black box testing  The actual execution of the previously written test cases  This testing is actually done by testers  they find the actual result of any functionality in the site and compare this result to the expected result  If they found any disparity then this is a bug  Acceptance testing  know as UAT  And this actually done by the tester as well as developers  management team  author  writers  and all who are involved in this project  To ensure the project is finally ready to be delivered with bugs free  Integration testing  The units of code  explained in point 1  are integrated with each other to complete the project  These units of codes may be written in different coding technology or may these are of different version so this testing is done by developers to ensure that all units of the code are compatible with other and there is no any issue of integration

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Depending on where you look  you ll get slightly different answers   I ve read about the subject a lot  and here s my distillation  again  these are slightly wooly and others may disagree   Unit Tests  Tests the smallest unit of functionality  typically a method function  e g  given a class with a particular state  calling x method on the class should cause y to happen    Unit tests should be focussed on one particular feature  e g   calling the pop method when the stack is empty should throw an InvalidOperationException    Everything it touches should be done in memory  this means that the test code and the code under test shouldn t    Call out into  non-trivial  collaborators Access the network   Hit a database Use the file system Spin up a thread etc    Any kind of dependency that is slow   hard to understand   initialise   manipulate should be stubbed mocked whatevered using the appropriate techniques so you can focus on what the unit of code is doing  not what its dependencies do    In short  unit tests are as simple as possible  easy to debug  reliable  due to reduced external factors   fast to execute and help to prove that the smallest building blocks of your program function as intended before they re put together   The caveat is that  although you can prove they work perfectly in isolation  the units of code may blow up when combined which brings us to      Integration Tests  Integration tests build on unit tests by combining the units of code and testing that the resulting combination functions correctly   This can be either the innards of one system  or combining multiple systems together to do something useful   Also  another thing that differentiates integration tests from unit tests is the environment   Integration tests can and will use threads  access the database or do whatever is required to ensure that all of the code and the different environment changes will work correctly     If you ve built some serialization code and unit tested its innards without touching the disk  how do you know that it ll work when you are loading and saving to disk   Maybe you forgot to flush and dispose filestreams   Maybe your file permissions are incorrect and you ve tested the innards using in memory streams   The only way to find out for sure is to test it  for real  using an environment that is closest to production   The main advantage is that they will find bugs that unit tests can t such as wiring bugs  e g  an instance of class A unexpectedly receives a null instance of B  and environment bugs  it runs fine on my single-CPU machine  but my colleague s 4 core machine can t pass the tests    The main disadvantage is that integration tests touch more code  are less reliable  failures are harder to diagnose and the tests are harder to maintain   Also  integration tests don t necessarily prove that a complete feature works   The user may not care about the internal details of my programs  but I do   Functional Tests  Functional tests check a particular feature for correctness by comparing the results for a given input against the specification   Functional tests don t concern themselves with intermediate results or side-effects  just the result  they don t care that after doing x  object y has state z   They are written to test part of the specification such as   calling function Square x  with the argument of 2 returns 4     Acceptance Tests  Acceptance testing seems to be split into two types   Standard acceptance testing involves performing tests on the full system  e g  using your web page via a web browser  to see whether the application s functionality satisfies the specification  E g   clicking a zoom icon should enlarge the document view by 25    There is no real continuum of results  just a pass or fail outcome    The advantage is that the tests are described in plain English and ensures the software  as a whole  is feature complete   The disadvantage is that you ve moved another level up the testing pyramid  Acceptance tests touch mountains of code  so tracking down a failure can be tricky     Also  in agile software development  user acceptance testing involves creating tests to mirror the user stories created by for the software s customer during development   If the tests pass  it means the software should meet the customer s requirements and the stories can be considered complete  An acceptance test suite is basically an executable specification written in a domain specific language that describes the tests in the language used by the users of the system   Conclusion  They re all complementary   Sometimes it s advantageous to focus on one type or to eschew them entirely   The main difference for me is that some of the tests look at things from a programmer s perspective  whereas others use a customer end user focus

[testing] What's the difference between unit, functional, acceptance, and integration tests?

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