Updated March 21, 2023
Difference Between Unit Test vs Functional Test
In this article, we will see an outline of the Unit Test vs Functional Test. Testing is the key function of product development that ensures quality. It is done at each stage to identify bugs and correct them. Unit Testing is a cornerstone of software development, introduced by Kent Beck. It’s been adopted by many organizations as a good practice ever since. At the primary stage, when the coding happens, the developer develops automated test cases using a unit test framework. When the test cases are executed, this framework logs test cases and flags them with severity. It can then be worked upon by the developer, and a consistent naming convention is followed for each unit test. This helps test the individual set of codes, functions or procedures in each module before they move on to the integration stage. The software’s functionality is tested in Functional Testing, where the outcome or result of the application is tested. The Functional tester does this. He Analyses the Expected and Actual outcome of test cases and flags them accordingly.
What is Unit and Functional Testing?
The unit and functional testing are explained in detail below:
Unit Testing:
A unit test is a popular practice adopted by many organizations as it primarily helps to eliminate the risk of having a bug in the codes. In order to test the functionality of each part of an Application, the set of codes are passed through Automated testing. The developer has a choice to do a Manual Unit test or an Automated Unit Test, while Automated testing is a preferred choice. Alternatively, a Step-by-step testing document can be developed to isolate the function to test it more rigorously. As it has a simulation of system structure, it follows the White Box Testing Technique. There are dozens of Automated tools available for a developer to use an Out-of-Box solution for Automated testing; some of them are:
- Nunit: This is a popular unit-testing framework used for all .net languages. It is an open-source tool. Manual scripts are allowed on this tool.
- JUnit: For Java programming language, this is a testing tool commonly used. It is freely available to use. It provides assertions to identify test methods.
- Jmockit: This is also an open-source tool and widely used for Unit testing. Recording and verification syntax is possible on this tool.
- PHPUnit: The ideal tool for PHP programmers for Unit testing. It has a pre-defined simulation that helps create a system structure for testing.
Functional Testing:
Testing of a system against the functional specifications or requirements is termed as Functional testing. Here, the processing steps aren’t tested, instead of the result of processing matters in the input-output process. Without making any environment assumptions, it simulates the actual system functionality. At this stage, the testing is done by a tester. The Black Box Testing technique is followed as the system’s internal logic is not known to the tester. The process is quite simple, where the application’s functionality is identified from the business requirements, Input and output data created basis the expected functionality and test cases are executed. Analysis of actual and expected outputs helps with the test results and plan to correct, if necessary. There are different types of Functional tests and several methods to execute them. This includes an integration test, Smoke test, regression test, Sanity test, and User acceptance test. Some of the methodology widely accepted are BDD testing and UI testing. All of them have a common objective to ensure the Software’s functionality; some tests are more rigorous and involve manual scripting, and some checks just the key functionality.
Head to Head Comparison between Unit Test vs Functional Test (Infographics)
Below are the top 9 comparisons between Unit Test vs Functional Test:
Key differences between Unit Test vs Functional Test
Let us discuss some key differences between Unit Test vs Functional Test in the following points:
- Finding Issues at an early stage has a lower cost to correct than the one at the implementation stage. Hence, the Unit test is critical at the development stage and Functional testing at the Acceptance Stage.
- Unit Test strictly follows the design document. While the developer is still coding, he passes the set of codes/functions through automated testing to ensure in sync with the design document. On the other hand, Functional testing can’t detect the defects if the test document is created from the design document. For effective functional testing, the test conditions should be created from Business requirements. This document clearly specifies the software’s expected functionality and the desired outcome, unlike the design document.
- As the unit test is done one code at a time, it can ensure the code is correct in the simulated system structure. As the codes are less interdependent, it is easier to resolve, and there are fewer chances of other codes getting impacted. However, it is not possible to test all execution paths. As it is a step-by-step check of the code quality, it can’t detect integration errors. Functional testing is useful just before Acceptance testing and Implementation.
Comparison Table of Unit Test vs Functional Test
The table below summarizes the comparisons between Unit Test vs Functional Test:
|
Unit Testing |
Functional Testing |
| It tests the Structure. | It tests the Functionality. |
| This is performed by the developer while he codes. | This is performed by a Functional tester in line with User/business documents. |
| The test happens while coding, one code at a time, ensuring the code correctness. | The test happens after the development is complete, and the software reaches the Acceptance testing phase. |
| The cost to quality is low as it impacts just one code/function. | The cost to correct is much higher as it impacts a set of codes that are interdependent. |
| Testing happens within the System Structure. | No System Structure Assumptions. |
| White Box Testing Method. | Black Box testing Method. |
| Third-party tool or created within the development group. | Test conditions created from Business requirements. |
| Helps in Debugging-process simplification by isolation the code that’s bad. | It helps in eliminating Functional errors. |
| Mostly, this is Automation testing. | It’s a Manual Testing process. |
Conclusion
Today, the customers expect the developers and SI companies to develop software of the highest quality. And that compels the companies to incorporate different testing stages as a part of the development process. Unit Testing is the key to achieve the bug-free codes for an evolving and competitive market. Yes, the developer has to spend those extra hours testing and correcting the errors. But it pays better – it ensures the code quality and helps with the coding in line with the design document. Functional testing identifies the functionality defects against the business document, therefore guiding to a perfect Software product in line with the customer expectations.
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