What is the difference between Unit, Integration, Regression and Acceptance Testing?

Asked 6/10, 2011 at 9:35 Answered 1/4, 2020 at 4:19

Solved unit-testing testing tdd integration-testing regression-testing

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Is there anyone that can clearly define these levels of testing as I find it difficult to differentiate when doing TDD or unit testing. Please if anyone can elaborate how, when to implement these?

Lowborn answered 6/10, 2011 at 9:35 Comment(2)

Possible duplicate of What is Unit test, Integration Test, Smoke test, Regression Test? – Gertrudis 30/12, 2016 at 17:57

Also see What's the difference between unit, functional, acceptance, and integration tests? – Witter 19/1, 2017 at 22:45

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Briefly:

Unit testing - You unit test each individual piece of code. Think each file or class.

Integration testing - When putting several units together that interact you need to conduct Integration testing to make sure that integrating these units together has not introduced any errors.

Regression testing - after integrating (and maybe fixing) you should run your unit tests again. This is regression testing to ensure that further changes have not broken any units that were already tested. The unit testing you already did has produced the unit tests that can be run again and again for regression testing.

Acceptance tests - when a user/customer/business receive the functionality they (or your test department) will conduct Acceptance tests to ensure that the functionality meets their requirements.

You might also like to investigate white box and black box testing. There are also performance and load testing, and testing of the "'ilities" to consider.

Again answered 6/10, 2011 at 9:42 Comment(2)

FYI, in Unit testing, the units being tested can be of various sizes. You could for instance unit test a group of classes, a single method, or even a s single method. Source: BlueJ chaptor 9.3 "Unit testing within BlueJ". – Scandinavia 9/11, 2019 at 22:23

So we don't write Regression Tests but rather it's the combination of running Unit Tests and Integration Tests after making a change (new feature or bug fix) to check that the system still works as it was intended to be ? I have implemented a Bug Fix lately (with another logic different than what was implemented) but then many Unit Tests failed. Is ok to adapt the tests to the new logic or does the logic have to apdapt to the Tests (implement as far as the Tests run successlly) ? – Flurried 3/11, 2020 at 18:42

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Unit test: when it fails, it tells you what piece of your code needs to be fixed.

Integration test: when it fails, it tells you that the pieces of your application are not working together as expected.

Acceptance test: when it fails, it tells you that the application is not doing what the customer expects it to do.

Regression test: when it fails, it tells you that the application no longer behaves the way it used to.

Antecedents answered 7/10, 2011 at 3:44 Comment(0)

Here's a simple explanation for each of the mentioned tests and when they are applicable:

Unit Test A unit test is performed on a self-contained unit (usually a class or method) and should be performed whenever a unit has been implemented or updating of a unit has been completed.

This means it's run whenever you've written a class/method, fixed a bug, changed functionality...

Integration Test Integration test aims to test how well several units interact with each other. This type of test should be performed Whenever a new form of communications has been established between units or the nature of their interaction have changed.

This means it's run whenever a recently written unit is integrated into the rest of the system or whenever a unit which is interacts with other systems has been updated (and successfully completed its unit tests).

Regression Test Regression tests are performed whenever anything has been changed in the system, in order to check that no new bugs have been introduced.

This means it's run after all patches, upgrades, bug fixes. Regression testing can be seen as a special case of combined unit test and integration test.

Acceptance Test Acceptance tests are performed whenever it is relevant to check that a subsystem (possibly the entire system) fulfils its entire specifications.

This means it's mainly run before finishing a new deliverable or announcing completion of a larger task. See this as your final check to see that you've really completed your goals before running to the client/boss and announcing victory.

This is at least the way I learned, though I'm sure there are other opposing views. Either way, I hope that helps.

Commie answered 6/10, 2011 at 10:10 Comment(3)

I can't really differentiate between regression testing and unit testing. I mean after each change/commit still you have your unit-tests being ran...and they can catch errors introduced by new code. Right? – Menke 3/5, 2017 at 18:35

@Honey Well, the regression test suite is mostly a selection of some or all of your unit and integration tests. It's a policy thing, how much regression testing you want to do. The main difference is that Unit tests are done in active development while regression tests is more something you use to check that previous projects don't break when you go back and patch them. – Commie 5/5, 2017 at 9:47

AFAIK you actually should not unit-test methods. If you test class you should treat it as a whole thing, so you test the class's public interface, not it's implementation details. Although you can unit-test the standalone function, that's fine. – Armbrecht 21/8, 2020 at 11:41

Unit Test: is my single method working correctly? (NO dependencies, or dependencies mocked)

Integration Test: are my two separately developed modules working corectly when put together?

Regression Test: Did I break anything by changing/writing new code? (running unit/integration tests with every commit is technically (automated) regression testing). More often used in context of QA - manual or automated.

Acceptance Test: testing done by client, that he "accepts" the delivered SW

Phenylalanine answered 20/8, 2016 at 11:33 Comment(0)

I'll try:

Unit test: a developer would write one to test an individual component or class.
Integration test: a more extensive test that would involve several components or packages that need to collaborate
Regression test: Making a single change to an application forces you to re-run ALL the tests and check out ALL the functionality.
Acceptance test: End users or QA do these prior to signing off to accept delivery of an application. It says "The app met my requirements."

Groundnut answered 6/10, 2011 at 9:43 Comment(0)

Can't comment (reputation to low :-| ) so...

@Andrejs makes a good point around differences between environments associated with each type of testing.

Unit tests are run typically on developers machine (and possibly during CI build) with mocked out dependencies to other resources/systems.

Integration tests by definition have to have (some degree) of availability of dependencies; the other resources and systems being called so the environment is more representative. Data for testing may be mocked or a small obfuscated subset of real production data.

UAT/Acceptance testing has to represent the real world experience to the QA and business teams accepting the software. So needs full integration and realistic data volumes and full masked/obfuscated data sets to deliver realistic performance and end user experience.

Other "ilities" are also likely to need the environment to be as close as possible to reality to simulate the production experience e.g. performance testing, security, ...

Fenestration answered 1/4, 2020 at 4:19 Comment(0)

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