Testing a unit independently from the modules and services of the application allows making up an asserted module.
Units are the first levels the bugs can happen and propagate further the entire application, so testing these smallest pieces prevents the undesirable possibility.
Unit Testing also postulates that the method returns an expected result, changes the state of the system, calls another function, and processes the exception during the test.
Testing a unit of code should run fast. Otherwise, it is a manifestation of the error in the process. It is essential to assert that integration with other components will not change the code's work. That means that apart from testing a unit, an integration test must be at hand, in case something causes a conflict.
Unit Testing Method
Implementation of the unit testing requires a thorough knowledge of the internal structure and design of the item. This type of testing uses a white-box testing method and goes beyond the user interface.
The unit usually has a few inputs and a single output, so the test runs through the code by choosing the first ones and defining the correct output.
By studying the implementation code of a unit and determining all the possible inputs, valid, invalid, and illegal included, the tester verifies the outputs against the anticipated outcomes.
Tips for Testing Types
The first thing to know about Unit Testing is that it should be regular and frequent.
Test script requires an appropriate framework for the language and should impact the system behavior.
The development and test environments should be isolated; test data should be close to that of the product.
After exposing the defect, a correspondent test is needed for further usage.
Test cases should be separated from each other by creating an abstract interface and implementing it with a mock object.
Covering all paths through the unit requires special attention, loop conditions in particular.
The unit test requires writing cases for behavior verification and performance validation and keeping track of scripts with the version control system.
Unit Testing Benefits
Testing the units allows maintaining the code by lessening the unexpected impact of the possible change.
Unit testing makes code modular and more reusable.
By preventing defects at the very beginning stage, Unit testing makes the development process faster and easier, sparing the efforts and costs that system testing or acceptance testing might require.