To define a Unit, it is the smallest part of the software application that is testable like functions, classes, procedures and interfaces. Unit Testing is a method in which individual units of source code are tested to make sure whether they are fit for use or not.
Some important notable points about unit testing are given below
- Software developers basically write and execute unit tests to ensure that particular unit of the software code meets its design, requirements and functional expectations
- The main objective of unit testing is to separate each part of the software code and test each individual part whether it is working as expected or not
- This means that it is necessary for any function or procedure of the software being developed that when a set of inputs are provided, it should return the expected output. If any invalid input is given by the unit, then it should be able to handle the failures without collapsing the entire system
- A written contract confirming that the piece of code is working correctly is provided at the end of unit testing, this contract in turn has several benefits
- Unit testing usually takes place before the integration is done. Following flow chart explains the flow of testing levels
Now, White Box Testing is a method using which unit testing is done. It usually takes place before the integration testing, as you can see in the flow chart diagram above. This unit testing is completely done by the developers to test pieces of the code written by them.
Advantages of Unit Testing
There are many advantages of unit testing. Some of the main advantages are given below
- In Unit testing, defects and failures are detected at a very early stage; here, developers test their own individual code before the integration is done, therefore, the issues that are found early are fixed early without letting them affect the other pieces of the code
- Unit testing is very useful in maintaining and changing the code when required; this is done by making each unit of code less interdependent so that unit testing can be done individually on each unit, this greatly reduces the impact of changes done in a unit code on the entire code
- Since the defects and failures are detected during the early stages, the cost of fixing them is reduced greatly, to get a mental picture, imagine a defect that was not detected in early stages but was then found during the later stages of software development like during system testing or acceptance testing, the cost of fixing this particular bug will be huge as that single change could affect the entire system
- Unit testing also helps in simplifying the debugging process, for instance, suppose a test fails, then only the latest changes that are made within the code needs to be debugged
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