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

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?

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.

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 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.

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.

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.

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.

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.

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

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?

• 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

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.

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.

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."

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.

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?

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.