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A Deep-Dive Into The World of Functional Testing



What is Software Testing?

Techniques of Testing

Functional Testing

1)Unit Testing

1a) Manual Testing

1b)Automation Testing

2)Integration Testing

2a)Big-Bang Testing

2b) Top-down Testing

2c) Bottom-up Testing

2d)Hybrid/Sandwich Testing

3)System Testing

3a)End-to-End Testing

3b)Black Box Testing

3c)Smoke Testing

3d)Sanity Testing

3e)Happy Path testing

3f)Monkey Testing

4)Acceptance Testing

4a)Alpha Testing

4b)Beta Testing

4c)Operational Acceptance Testing



In this blog, we are going to see the different types of functional Testing and how it is performed in detail.

What is Software Testing?

Software testing is the act of examining the artifacts and the behavior of the software under test by validation and verification. Testing provides an objective, independent view of the software to allow the business to appreciate and understand the risks of software implementation.

Software testing can be performed at different levels of the software development process. Performing testing activities at multiple levels help in early identification of bugs and better quality of software product.

Techniques of Testing

Test techniques include, but are not necessarily limited to:

· analyzing the product requirements for completeness and correctness in various contexts like industry perspective, business perspective, feasibility and viability of implementation, usability, performance, security, infrastructure considerations, etc.

· reviewing the product architecture and the overall design of the product

· working with product developers on improvement in coding techniques, design patterns, tests that can be written as part of code based on various techniques like boundary conditions, etc.

· executing a program or application with the intent of examining behavior

· reviewing the deployment infrastructure and associated scripts and automation

· take part in production activities by using monitoring and observability techniques

Software Testing is broadly classified in two types:

1) Functional Testing

2) Non-Functional testing

Functional Testing:

Functional Testing means to verify that each function of the software application behaves in a way that is specified in the requirement document.

Functional Testing is used to test all the functionalities by providing appropriate input to verify whether the actual output is matching the expected output.

The four important levels of functional testing are:

Ø Unit Testing

Ø Integration Testing

Ø System Testing

Ø Acceptance Testing

1.Unit Testing

Unit Testing is also called as Module Testing or Component Testing, which is done to check whether the individual unit or module of the source code is working properly. Unit Testing is done during the development (coding phase) of an application by the developers.

Unit Tests isolate a section of code and verify its correctness. A unit may be an individual function, method, procedure, module, or object. Developers often use test automation tools such as NUnit, Xunit, JUnit for the test execution.

1a) Manual Testing

Manual testing is a way of testing software in which test cases are run manually instead of with an automated tool. The tester will run all the test cases manually from the end user's point of view. It checks to see if the application works the way the requirements document says it should. Almost all software projects conclude once test cases have been prepared and executed.

1b) Automation Testing

A coder generally uses a Unit Test Framework to develop automated test cases. Using an automation framework, the developer codes criteria into the test to verify the correctness of the code. During execution of the test cases, the framework logs failing test cases.

Unit Testing provide the following benefits:

· It provides the ability to test the software in its component pieces.

· Performs checks to ensure that the program code is high quality and correct.

· The team can carry out unit testing before the completion of the development process.

· Unit testing results in modular code, making it easier to reuse the modules.

· It makes changes easier to implement and streamlines documentation and integration.

· It helps to streamline the debugging process.

2.Integration Testing

Integration testing is the phase in software testing in which individual software modules are combined and tested as a group.

Integration testing is conducted to evaluate the compliance of a system or component with specified functional requirements.

Integration testing takes as its input modules that have been unit tested, groups them in larger aggregates, applies tests defined in an integration test plan to those aggregates, and delivers as its output the integrated system ready for system testing.

Some different types of integration testing are:

· Big-Bang Testing

· Top-down Testing

· Bottom-up Testing

· Hybrid/Sandwich Testing

Other Integration Patterns are collaboration integration, backbone integration, layer integration, client-server integration, distributed services integration, and high-frequency integration.

2a. In Big-Bang Testing,

Combining all the modules once and verifying the functionality after completion of individual module testing. Here, most of the developed modules are coupled together to form a complete software system or major part of the system and then used for integration testing. This method is very effective for saving time in the integration testing process.

2b. In Bottom-Up Testing,

The lowest level components are tested first, and are then used to facilitate the testing of higher-level components. The process is repeated until the component at the top of the hierarchy is tested. All the bottom or low-level modules, procedures or functions are integrated and then tested.

After the integration testing of lower-level integrated modules, the next level of modules will be formed and can be used for integration testing.

This approach is helpful only when all or most of the modules of the same development level are ready. This method also helps to determine the levels of software developed and makes it easier to report testing progress in the form of a percentage.

2c. In Top-Down Testing,

Testing takes place from top to bottom. High-level modules are tested first and then low-level modules and finally integrating the low-level modules to a high level to ensure the system is working as intended. Stubs are used as a temporary module if a module is not ready for integration testing.

2d. Hybrid/Sandwich Testing

Combines top-down testing with bottom-up testing. One limitation to this sort of testing is that any conditions not stated in specified integration tests, outside of the confirmation of the execution of design items, will generally not be tested.

3.System Testing

Testing the fully integrated application to evaluate the system’s compliance with its specified requirements is called System Testing. It is a level of testing that validates the complete and fully integrated software product. Verifying the completed system to ensure that the application works as intended or not.

3a) End to End Testing

It involves testing a complete application environment in a situation that mimics real-world use, such as interacting with a database, using network communications, or interacting with other hardware, applications, or systems if appropriate.

3b) Black Box Testing

Black Box Testing is a software testing method in which testers evaluate the functionality of the software under test without looking at the internal code structure.

3c) Smoke Testing

Smoke testing is performed to verify that basic and critical functionality of the system under test is working fine at a very high level.

Whenever a new build is provided by the development team, then the Software Testing team validates the build and ensures that no major issue exists. The testing team will ensure that the build is stable, and a detailed level of testing will be carried out further.

3d) Sanity Testing

Sanity testing is performed on a system to verify that newly added functionality or bug fixes are working fine. Sanity testing is done on stable build. It is a subset of the regression test.

3e) Happy Path Testing

The objective of Happy Path Testing is to test an application successfully on a positive flow. It does not look for negative or error conditions. The focus is only on valid and positive inputs through which the application generates the expected output.

3f) Monkey Testing

Perform abnormal action on the application deliberately to verify the stability of the application.

Monkey Testing is carried out by a tester, assuming that if a monkey uses the application, then how random input and values will be entered by the Monkey without any knowledge or understanding of the application.

The objective of Monkey Testing is to check if an application or system gets crashed by providing random input values/data. Monkey Testing is performed randomly, no test cases are scripted, and it is not necessary to be aware of the full functionality of the system.

4.Acceptance Testing

Acceptance testing is a type of testing where client/business/customer test the software with real time business scenarios.

The client accepts the software only when all the features and functionalities work as expected. This is the last phase of testing, after which the software goes into production. This is also called User Acceptance Testing (UAT).

4a) Alpha Testing

Alpha testing is a type of acceptance testing performed by the team in an organization to find as many defects as possible before releasing software to custom Alpha testing is done by the in-house developers (who developed the software) and testers.

Sometimes alpha testing is done by the client or outsourcing team with the presence of developers or testers.

It has two phases:

• In the first phase of alpha testing, the software is tested by in-house developers. They use debugger software. The goal is to catch bugs quickly.

• In the second phase of alpha testing, the software is handed over to the software QA people, for additional testing in an environment that is similar to the intended users.

4b) Beta Testing

Beta Testing is a type of software testing which is carried out by the clients/customers. It is performed in the Real Environment before releasing the product to the market for the actual end-users.

Beta Testing is carried out to ensure that there are no major failures in the software or product, and it satisfies the business requirements from an end-user perspective. Beta Testing is successful when the customer accepts the software.

Usually, this testing is typically done by the end-users. This is the final testing done before releasing the application for commercial purposes. Usually, the Beta version of the software or product released is limited to a certain number of users in a specific area.

So, the end-user uses the software and shares the feedback with the company. The company then takes necessary action before releasing the software worldwide.

4c) Operational acceptance testing (OAT)

Operational acceptance testing of the system is performed by operations or system administration staff in the production environment. The purpose of operational acceptance testing is to make sure that the system administrators can keep the system working properly for the users in a real-time environment.


The efficiency of any application functions based on customer requirements, is covered in functional testing. Functional testing can be undoubtedly considered as the most important of all because it directly deals with the customer perspective and customer requirements. Hope you got an idea about different functional testing types to check every functionality of the application.

Happy Testing!!!

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