9 Principles of unit testing

Unit testing is the first level of testing a software product or application and hence a valuable and important testing method. It is performed before the integration testing process. It identifies bugs and fixes them right in the initial stages of software development and thus fixes it at the earliest. The individual components are properly tested using the unit testing method. Gradually, the software product or application can be passed on to subsequent levels of testing. In this article, you will get to know the nine principles of unit testing.  

What is unit testing? 

It is a testing method wherein individual components of code known as "units" are tested. It is the first phase of the Software Testing Life Cycle (STLC) process. Test cases are written by developers for their code to make sure that they work and behave as per the required expectations.  

Following are the nine principles of unit testing: 

1. Small parts of the codebase are tested: The complex software system is broken down into testable, manageable units. When a small portion of the code is focused and worked upon, then there is a sort of assurance that each part functions correctly before they are integrated. 

2. The importance of repeatability and consistency: When a test is run multiple times under the same conditions then it should also be able to produce the same outcome. There will be confusion if inconsistent results are derived and it will be difficult to diagnose and fix problems.  

3. The significance of automation: Developers take the initiative to write automated unit test scripts through which the unit tests are run automatically to assess the code functionality. 

4. Simple tests should be considered: The tests should be kept with low cyclomatic complexity. Cyclomatic complexity is a code metric through which a number of possible execution paths are indicated and a particular method can be followed.  

5. Implementation logic shouldn't be duplicated: Those test cases that are repetitive should be remediated using parameterized tests.  

6. Tests should be readable: The tests need to be kept simple. If it is hard to read tests then the bugs can be misunderstood and introduced more likely by the developers. Hence, test readability is advocated. As a form of documentation, test cases become double.    

7. The value of deterministic tests: This means that the same behavior should be presented by the tests if there are no changes that have been done while the code was under test. There will be scenarios wherein the code that is being tested without undergoing any change might pass or fail and in such situation, the concerned team perceives it as random or arbitrary. This in turn means that if the tests aren't deterministic, then developers may doubt the reliability of tests. 

8. Considering the build process: The whole process of running the tests should be automated and if they fail then the necessary action can be taken by the team. Hence, the unit tests should be executed by the build process and ensure that when a test fails then there should be a broken build. 

9. Components should be isolated: Isolation of the unit that is being tested from any external dependencies and the rest of the code. The idea behind isolation is to make sure that the test is focused on the unit's functionality and will not be affected by other parts of the system. Accurate results and precise testing can be expected when components are isolated. The possible sources of errors are narrowed down and thus help in finding and fixing issues easily.