What are unit tests integration tests smoke tests and regression tests

Question

What are unit tests  integration tests  smoke tests  and regression tests   What are the differences between them and which tools can I use for each of them   For example  I use JUnit and NUnit for unit testing and integration testing  Are there any tools for the last two  smoke testing or regression testing

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Unit Testing

Unit testing is usually done by the developers side, whereas testers are partly evolved in this type of testing where testing is done unit by unit. In Java JUnit test cases can also be possible to test whether the written code is perfectly designed or not.

Integration Testing:

This type of testing is possible after the unit testing when all/some components are integrated. This type of testing will make sure that when components are integrated, do they affect each others' working capabilities or functionalities?

Smoke Testing

This type of testing is done at the last when system is integrated successfully and ready to go on production server.

This type of testing will make sure that every important functionality from start to end is working fine and system is ready to deploy on production server.

Regression Testing

This type of testing is important to test that unintended/unwanted defects are not present in the system when developer fixed some issues. This testing also make sure that all the bugs are successfully solved and because of that no other issues are occurred.

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Answer from one of the best websites for software testing techniques   Types of software testing     complete list click here       It s quite a long description  and I m not going to paste it here  but it may be helpful for someone who wants to know all the testing techniques

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Unit Testing  It always performs by developer after their development done to find out issue from their testing side before they make any requirement ready for QA   Integration Testing  It means tester have to verify module to sub module verification when some data function output are drive to one module to other module  Or in your system if using third party tool which using your system data for integrate   Smoke Testing  tester performed to verify system for high-level testing and trying to find out show stopper bug before changes or code goes live   Regression Testing  Tester performed regression for verification of existing functionality due to changes  implemented in system for newly enhancement or changes in system

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Smoke and sanity testing are both performed after a software build to identify whether to start testing  Sanity may or may not be executed after smoke testing  They can be executed separately or at the same time - sanity being immediately after smoke   Because sanity testing is more in-depth and takes more time  in most cases it is well worth to be automated   Smoke testing usually takes no longer than 5-30 minutes for execution  It is more general  it checks a small number of core functionalities of the whole system  in order to verify that the stability of the software is good enough for further testing and that there are no issues  blocking the run of the planned test cases   Sanity testing is more detailed than smoke and may take from 15 minutes up to a whole day  depending on the scale of the new build  It is a more specialized type of acceptance testing  performed after progression or re-testing  It checks the core features of certain new functionalities and or bug fixes together with some closely related to them features  in order to verify that they are functioning as to the required operational logic  before regression testing can be executed at a larger scale

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REGRESSION TESTING-   A regression test re-runs previous tests against the changed software to ensure that the changes made in the current software do not affect the functionality of the existing software

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Unit test  Specify and test one point of the contract of single method of a class  This should have a very narrow and well defined scope  Complex dependencies and interactions to the outside world are stubbed or mocked  Integration test  Test the correct inter-operation of multiple subsystems  There is whole spectrum there  from testing integration between two classes  to testing integration with the production environment  Smoke test  aka sanity check   A simple integration test where we just check that when the system under test is invoked it returns normally and does not blow up    Smoke testing is both an analogy with electronics  where the first test occurs when powering up a circuit  if it smokes  it s bad          and  apparently  with plumbing  where a system of pipes is literally filled by smoke and then checked visually  If anything smokes  the system is leaky   Regression test  A test that was written when a bug was fixed  It ensures that this specific bug will not occur again  The full name is  non-regression test   It can also be a test made prior to changing an application to make sure the application provides the same outcome    To this  I will add    Acceptance test  Test that a feature or use case is correctly implemented  It is similar to an integration test  but with a focus on the use case to provide rather than on the components involved  System test  Tests a system as a black box  Dependencies on other systems are often mocked or stubbed during the test  otherwise it would be more of an integration test   Pre-flight check  Tests that are repeated in a production-like environment  to alleviate the  builds on my machine  syndrome  Often this is realized by doing an acceptance or smoke test in a production like environment

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Everyone will have slightly different definitions  and there are often grey areas  However    Unit test  does this one little bit  as isolated as possible  work  Integration test  do these two  or more  components work together  Smoke test  does this whole system  as close to being a production system as possible  hang together reasonably well   i e  are we reasonably confident it won t create a black hole   Regression test  have we inadvertently re-introduced any bugs we d previously fixed

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Unit testing is directed at the smallest part of the implementation possible  In Java this means you are testing a single class  If the class depends on other classes these are faked   When your test calls more than one class  it s an integration test   Full test suites can take a long time to run  so after a change many teams run some quick to complete tests to detect significant breakages  For example  you have broken the URIs to essential resources  These are the smoke tests   Regression tests run on every build and allow you to refactor effectively by catching what you break  Any kind of test can be regression test  but I find unit tests are most helpful finding the source of fault

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There are some good answers already  but I would like further refine them   Unit testing is the only form of white box testing here  The others are black box testing  White box testing means that you know the input  you know the inner workings of the mechanism and can inspect it and you know the output  With black box testing you only know what the input is and what the output should be    So clearly unit testing is the only white box testing here    Unit testing test specific pieces of code  Usually methods   Integration testing test whether your new feature piece of software can integrate with everything else  Regression testing  This is testing done to make sure you haven t broken anything  Everything that used to work should still work  Smoke testing is done as a quick test to make sure everything looks okay before you get involved in the more vigorous testing

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Regression test - Is a type of software testing where we try to cover or check around the bug fix  The functionality around the bug fix should not get changed or altered due to the fix provided  Issues found in such process are called as regression issues   Smoke Testing  Is a kind of testing done to decide whether to accept the build software for further QA testing

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I just wanted to add and give some more context on why we have these levels of test  what they really mean with examples  Mike Cohn in his book    Succeeding with Agile    came up with the    Testing Pyramid    as a way to approach automated tests in projects  There are various interpretations of this model  The model explains what kind of automated tests need to be created  how fast they can give feedback on the application under test and who writes these tests   There are basically 3 levels of automated testing needed for any project and they are as follows   Unit Tests- These test the smallest component of your software application  This could literally be one function in a code which computes a value based on some inputs  This function is part of several other functions of the hardware software codebase that makes up the application    For example - Let   s take a web based calculator application  The smallest components of this application that needs to be unit tested could be a function that performs addition  another that performs subtraction and so on  All these small functions put together makes up the calculator application   Historically developer writes these tests as they are usually written in the same programming language as the software application  Unit testing frameworks such as JUnit and NUnit  for java   MSTest  for C  and  NET  and Jasmine Mocha  for JavaScript  are used for this purpose   The biggest advantage of unit tests are  they run really fast underneath the UI and we can get quick feedback about the application  This should comprise more than 50  of your automated tests   API Integration Tests- These test various components of the software system together  The components could include testing databases  API   s  Application Programming Interface   3rd party tools and services along with the application    For example - In our calculator example above  the web application may use a database to store values  use API   s to do some server side validations and it may use a 3rd party tool service to publish results to the cloud to make it available across different platforms   Historically a developer or technical QA would write these tests using various tools such as Postman  SoapUI  JMeter and other tools like Testim   These run much faster than UI tests as they still run underneath the hood but may consume a little more time than unit tests as it has to check the communication between various independent components of the system and ensure they have seamless integration  This should comprise more that 30  of the automated tests   UI Tests- Finally  we have tests that validate the UI of the application  These tests are usually written to test end to end flows through the application    For example - In the calculator application  an end to end flow could be  opening up the browser-  Entering the calculator application url  -  Logging in with username password -  Opening up the calculator application -  Performing some operations on the calculator -  verifying those results from the UI -  Logging out of the application  This could be one end to end flow that would be a good candidate for UI automation   Historically  technical QA   s or manual testers write UI tests  They use open source frameworks like Selenium or UI testing platforms like Testim to author  execute and maintain the tests  These tests give more visual feedback as you can see how the tests are running  the difference between the expected and actual results through screenshots  logs  test reports    The biggest limitation of UI tests is  they are relatively slow compared to Unit and API level tests  So  it should comprise only 10-20  of the overall automated tests   The next two types of tests can vary based on your project but the idea is-  Smoke Tests  This can be a combination of the above 3 levels of testing  The idea is to run it during every code check in and ensure the critical functionalities of the system are still working as expected  after the new code changes are merged  They typically need to run with 5 - 10 mins to get faster feedback on failures  Regression Tests  They usually are run once a day at least and cover various functionalities of the system  They ensure the application is still working as expected  They are more details than the smoke tests and cover more scenarios of the application including the non-critical ones

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Smoke tests have been explained here already and is simple  Regression tests come under integration tests   Automated tests can be divided into just two   Unit tests and integration tests  this is all that matters   I would call use the phrase  long test   LT  for all tests like integration tests  functional tests  regression tests  UI tests  etc  And unit tests as  short test    An LT example could be  automatically loading a web page  logging in to the account and buying a book  If the test passes it is more likely to run on live site the same way hence the  better sleep  reference   Long   distance between web page  start  and database  end    And this is a great article discussing the benefits of integration testing  long test  over unit testing

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A new test category I ve just become aware of is the canary test  A canary test is an automated  non-destructive test that is run on a regular basis in a live environment  such that if it ever fails  something really bad has happened   Examples might be    Has data that should only ever be available in development testy appeared live  Has a background process failed to run  Can a user logon

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Unit test  an automatic test to test the internal workings of a class  It should be a stand-alone test which is not related to other resources  Integration test  an automatic test that is done on an environment  so similar to unit tests but with external resources  db  disk access  Regression test  after implementing new features or bug fixes  you re-test scenarios which worked in the past  Here you cover the possibility in which your new features break existing features  Smoke testing  first tests on which testers can conclude if they will continue testing

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Unit test  testing of an individual module or independent component in an application is known to be unit testing  The unit testing will be done by the 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   Smoke test  In a smoke test they check the application in a shallow and wide manner  In smoke testing they check the main functionality of the application  If there is any blocker issue in the application they will report to developer team  and the developing team will fix it and rectify the defect  and give it back to the testing team  Now testing team will check all the modules to verify that changes made in one module will impact the other module or not  In smoke testing the test cases are scripted   Regression testing executing the same test cases repeatedly to ensure tat the unchanged module does not cause any defect  Regression testting comes under functional testing

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Integration testing  Integration testing is the integrate another element Smoke testing  Smoke testing is also known as build version testing  Smoke testing is the initial testing process exercised to check whether the software under test is ready stable for further testing  Regression testing  Regression testing is repeated testing  Whether new software is effected in another module or not  Unit testing  It is a white box testing  Only developers involve in it

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Unit test  Verifying that particular component  i e   class  created or modified functions as designed  This test can be manual or automated  but it does not move beyond the boundary of the component   Integration test  Verifying that the interaction of particular components function as designed  Integration tests can be performed at the unit level or the system level  These tests can be manual or automated   Regression test  Verifying that new defects are not introduced into existing code  These tests can be manual or automated   Depending upon your SDLC  waterfall  RUP  agile  etc   particular tests may be performed in  phases  or may all be performed  more or less  at the same time  For example  unit testing may be limited to developers who then turn the code over to testers for integration and regression testing  However  another approach might have developers doing unit testing and some level of integration and regression testing  using a TDD approach along with continuous integration and automated unit and regression tests    The tool set will depend largely on the codebase  but there are many open source tools for unit testing  JUnit   HP s  Mercury  QTP or Borland s Silk Test are both tools for automated integration and regression testing

[unit-testing] What are unit tests, integration tests, smoke tests, and regression tests?

Unit Testing

Integration Testing:

Smoke Testing

Regression Testing

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