Primary test performed on software is the ‘Unit Testing’ to see if a standalone module is working as per the requirements. This type of testing is mostly done by the developers.
Testing performed on a single, standalone module or unit of code to ensure correctness of the particular module. Focuses on implementation logic, so the idea is to write test cases for every method in the module.
Unit tests are created by programmers or sometimes occasionally by white box testers during the development process. Each test case are independent form each other substitutes like method subs, mock objects, fake and test harnesses can be used to assist testing a module in isolation. Software developers will typically write and run the unit tests to ensure whether the code meets its design and behaves as intended. Its implementation can vary from being very manual to formalize as part of build automation.
Benefits of Unit testing
The goal of unit testing is to isolate each part of the program and show that the individual parts are correct.
This isolated testing provides four main benefits:
- Flexibility when changes are required.
- Facilitates integration
- Ensures documentation of the code
- Separation of interface from implementation.
Unit testing allows the programmers to refactor code at a later date and make sure the module works correctly still. The procedure is to write test cases for all methods and functions so that whenever a change causes a fault, it can be identified quickly and fixed also. Programmers check whether a piece of code is still working properly or not with the readily available unit tests which makes it easy.
In the unit testing environment through the inherent practice of sustained maintenance unit tests will continue to accurately reflect the intended use of executable and code in the face of any changes. So depending upon established development practices and unit test coverage, we can maintain up to the second accuracy.
Unit Testing Simplifies Integration
Unit testing reduces the uncertainty in the units themselves and can be used in the bottom up style approach. Since testing the parts of a program first and then testing the sum of its parts integration testing becomes easier. An elaborated hierarchy of unit tests does not equal the integration testing. Integration with peripheral s units should be included in integration tests but not in the unit tests. Integration testing typically relies on humans manual testing, global scope testing or high level testing can be difficult to automate, so that manual testing often appears faster and cheaper in the industry.
Documentation in Unit Testing
Living documentation of the system is provided by the unit testing. Developers learn what functionality is provided by a unit and how it can be used to look at the unit tests to gain a basic understanding of the units.
Unit tests characteristics are critical to the success of the unit. So these characteristics can indicate appropriate and inappropriate use of a unit as well as the negative behaviors that has to be trapped by the unit. A unit test case documents these critical characteristics within and itself although many software development environments don’t rely upon the code to document the product in the development.
Limitations of Unit Testing
Every error in the testing cannot be expected to be caught in the testing. It is impossible to evaluate execution path in all but the most trivial programs. Unit testing is true for the same. So additionally unit testing by definition only tests the functionality of ht units themselves. Therefore, it will not catch integration errors or broader system level errors such as non functional test area such as performance and functions performed across the multiple units. Unit testing can be done in conjunction with other software testing activities. Like the other forms of software testing, unit tests can only show the presence of errors and they should not show the absence of errors.
Rigorous discipline is needed thought out the software development process to obtain the intended benefits from unit testing. It is essential to keep the careful records not only of the tests which has been performed, but also of all changes that have been made to the source code of this or any other unit in the software. Use of a version control system is very essential so that a later version of the unit fails a particular test that it had passed previously, so this version control software provides a list of source code changes done if any that has been applied to the unit since that time.
Even it’s essential to implement a sustainable process for ensuring the test case failures are reviewed daily and addressed quickly. So such process is not implemented and ingrained into the team’s workflow, so the application will evolve out of sync with the unit test suite, by increasing false positives and reducing the effectiveness of the test suite.
Techniques in Unit Testing
Unit testing is automated commonly, but still it can be performed manually. The IEEE does not favor one over the other. A manual to the unit testing may employ a step-by-step instructional document. The objective in unit testing is to isolate a unit and validate its correctness. Automation is efficient for achieving this and enables the benefits in the article. If not planned carefully, a careless manual unit test case may execute as an integration test case that involves many software components, and thus the achievement of most if not all the goals established for unit testing.
To realize the effect of isolation while using an automated approach, the unit or code body under test is executed within a framework outside of its natural environment. In simple words we can say it is executed outside of the product or calling context for which it was originally created. So testing in such isolated manner reveals unnecessary dependencies between the code being tested and other units or data spaces in the product and these dependencies can be eliminated.
By using an automation framework, the developer codes criteria into the test to verify the unit’s correctness. During the test case execution, the framework logs tests that fail any criterion so many frameworks will be automatically flag these failed test cases reports the summary. Depending upon the severity of a failure, the framework may halt subsequent testing.
A unit testing is traditionally a motivator for programmers to create cohesive and decoupled code bodies. So this practice helps the healthy habits in software development design patterns, unit testing and refactoring the work often together so that the best solution may emerge.