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A Complete Guide To Functional Testing

In this technological and digital era, everyone desires to have defect-free and error-free software products. To ensure the software is defect-free, software testing plays a vital role in enhancing the software’s quality, performance, and reliability. Functional Testing is one of the software testing types that ensures top-notch and high-quality software. 

What Is Functional Testing?

Functional testing is a software testing type, where each part of the software is tested against user specifications and functional requirements. In other terms, this testing ensures that the software’s each functionality functions correctly concerning the user requirements and specifications. The specific input is provided to each function of the software, and the resulting output is compared with the expected outcome. The system should behave as specified in the user’s requirements specification.

Function system testing is a kind of block box technique, which does not focus on the application’s source code. Instead, it focuses on checking the application’s API, security, user interface, database, client/server communication, and much other Application Under Test (AUT) functions. It primarily concentrates on the system’s basic usability, accessibility, main characteristics, and error condition. As it is a black box testing technique, testers test the system’s functions without knowing its internal working. 

Non-functional testing is carried out to test the system for the way it operates. The system is tested against non-functional parameters. This type of testing’s primary objective is to enhance the system’s efficiency, usability, portability, and maintainability. 

Difference Between Functional And Non-Functional Testing

Functional TestingNon-Functional Testing
This testing tests the system against the functional parameters and requirements specified by the client. This testing tests the software for non-functional parameters, like the system’s performance, reliability, scalability, etc. 
It takes business requirements as inputs. It takes performance parameters, like scalability, speed, etc., as inputs. 
It defines what the system performs. It defines how the system performs. 
Testers feel it is easy to execute this testing manually. This testing is relatively tougher to perform manually. 
The system’s behaviour is enhanced. The system’s performance is enhanced. 
Examples – Unit TestingRegression TestingSmoke TestingIntegration TestingExamples – Stress TestingLoad TestingPerformance TestingScalability Testing

How To Perform Functional Testing?

Before we discuss the functional system testing process, we shall glance at some significant parameters that need to be tested in this testing. This testing primarily tests the below system functions –

  • Basic Usability: Basic usability implies whether users can navigate and use the system hassle-free. 
  • Error Conditions: Testers test the system to verify whether the error messages are correctly displayed to users. 
  • Accessibility: It verifies whether a particular user can access the system. 
  • Mainline Functions: Testers test the primary features or functions of the system. 

Now, let us move towards the steps followed to perform the functional testing process. 

  1. Firstly, it is necessary to understand and recognize the functional requirements specified by the client. 
  2. Depending upon the client’s requirements, identify test input for each system’s function. 
  3. Perform the test with the test input and observe the outcome. Compare the resulting outcome with the test input. 
  4. Compute test cases and then compare expected and computed results. 

A plethora of software tools is available in the market today to execute functional testing, like Selenium, SoapUI, TestComplete, QTP, LoadRunner, JUnit, Watir, etc. 

Functional Testing Types

There are different types of functional system testing, and each of the testing types is utilized depending on the scenarios. Let us discuss each testing type briefly. 

  1. Unit Testing

Unit testing is performed to test individual components or units of the system. The major objective of the unit testing is to check whether the system’s every unit or component functions as expected. During the application’s development process, unit testing is performed first. The developer who writes the code for the software’s every unit is responsible for performing the unit testing. 

  1. Integration Testing

As its name indicates, integration testing is performed by combining all units of the system together. The integration system’s major goal is to identify defects or faults in the interaction between clubbed components. 

  1. Regression Testing

Regression testing is performed to verify that any changes made in the system’s function do not affect the existing function. Any new modifications to the system should not have adverse or side effects on the existing functionalities. The system should function as expected, even the modifications, like inserting a new code, fixing bugs, etc., are made. 

  1. Smoke Testing

Smoke testing ensures that the deployed system build is steady and stable. It indicates a green signal to the Quality Assurance team to carry out the further process of software testing. It is also referred to as Confidence Testing or Build Verification Testing.

  1. Sanity Testing

Sanity Testing is carried out when the system’s build is ready with some minute modifications in functions or code to fix bugs or defects. This testing ensures that modifications to fix bugs do not result in further defects. It verifies that particular functionality functions as per the user’s or client’s requirements. 

Functional Testing Example

Consider a portal for employees, where they can log-in to their accounts using a username and password. Therefore, there are two text fields on the portal’s log-in page – one for username and the other for a password, and two buttons – one for log-in and the other for cancellation. For the username and password, there are certain specifications as follows – 

  • For the username, the specification is that employees need to enter at least six characters- letters from a-z and A-Z, special symbols, like underscore, a hyphen, and period, and numbers from 0 to 9. Always start the username with the number or a letter and not the special character. 
  • For the password field, the specification is that employees need to set their passwords at least six characters, containing all special symbols, letters (a-z, A-Z), and numbers (0-9). 

Both username and password field cannot be blank. If the user enters both fields as per the specifications and enters the log-in button, they can access the portal. This example includes positive and negative testing. The positive testing implies at least basic requirements are satisfied, whereas, the negative testing means the system functions correctly to unexpected data.

Do You Know?
1. What is Regression Testing?
2. What is White Box testing?
3. What is black box testing?
4. What is Exploratory Testing?
5. What is Functional testing?

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