What is Unit test Integration Test Smoke test Regression Test

What is Unit test, Integration Test, Smoke test, Regression Test?

What is Unit test, Integration Test, Smoke test, Regression Test and 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 Smoke Test or Regression Test tools?

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.

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 intergrate 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.

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. It is an analogy with electronics, where the first test occurs when powering up a circuit: if it smokes, it's bad.

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 worthed 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 in larger scale.

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.

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

People claim smoke testing comes from plumbing where smoke is pumped in the system of pipes before it's connected to the water supply. If any smoke comes out, the pipes are not properly sealed. It might be more historically accurate, but I find it is less funny.