• What is functional testing?
  • Step-by-step approach to functional testing
  • Types of functional testing
  • Automated functional testing

This handbook will cover the different types of functional testing methods and how they help to deploy software with the least possible defects.

What is functional testing?

Core software functionalities need to be tested in real time, to ensure that the most important business requirements are met. Each functionality is scrutinised against its technical specification to ensure the usability, accessibility, and overall conformance of the software.

A step-by-step approach to functional testing

  • Step 1: Testers must identify how a basic function is expected to perform, keeping in mind the end user.
  • Step 2: Test scenarios must be created with the intended response for every action.
  • Step 3: Test data for the test scenarios must be generated to establish the desired results.
  • Step 4: The test cases must be executed to validate the desired outcome against the requirement.
  • Step 5: Comparing the actual outcome with the expected outcome will determine if the software is functioning as desired.

Types of functional testing

Unit testing

Testing the smallest unit of logical code as an isolated component is known as unit testing. It's considered a part of the development phase and is often carried out by the developers who wrote the code. This is because unit testing is a white box technique that relies on the internal code, design, and implementation. Unit testing is often automated to improve the quality of tests and the productivity of developers.

Use case scenario: Imagine you want to build an e-commerce platform. The search functionality is the single most important component of the software for your business. When a keyword is entered in the search bar, corresponding search results should be displayed. A unit test needs to be performed to verify if the search algorithm works correctly and performs the required function.

Importance of unit testing:

  • In the above scenario, when a user makes a keyword search for "watches" and the application throws an error—"No results found"—this could potentially cause revenue leakage. Identifying these bugs in the early phases of development results in early fixes.
  • Unit testing enables frequent iterations that save a lot of time and effort. This facilitates faster releases.
  • Insights gained from unit testing can help in understanding the conditions under which a test fails. When the source of the problem is identified, testers don't need to waste time testing the entire system. This significantly reduces defect costs.
  • Individual functionalities are tested exhaustively and documented, improving overall code quality. This provides clarity on how the codebase is expected to function.

Integration testing

Integration testing is performed to verify if the individual components of an application interact with each other as intended. Unlike unit testing, integration testing requires developers and testers to collaborate. Different methods are employed to test different kinds of integrations. Automating your integration testing improves test coverage, shortens the feedback loop, reduces manual effort, saves time, and cuts costs.

Use case scenario: If a user who lands on your e-commerce platform decides to purchase a luxury watch, they perform a series of actions. They view the product, add it to the shopping cart, fill in the delivery details, click to check out, get directed to the payment gateway, and pay to complete the transaction and receive the e-invoice via an email confirmation.

This entire workflow needs to be verified, as the interactions create dependencies with other modules, such as payment gateways, emailing the client, and more. The purpose of integration testing is to ensure that the expected results in each step are successfully achieved.

Importance of integration testing:

  • In our e-commerce example, an error occurs when the app does not redirect the user to the payment gateway upon clicking to check out. Interaction between the different components of the software is tested to verify if they work correctly together, improving the reliability of the system as a whole.
  • The overall quality and efficiency of the software can be improved by eliminating compatibility and data-sync issues in the early phases of development.
  • Verifying the workflow ensures that the software functions as desired in a logical sequence, improving the overall performance.
  • Integration testing checks the interfaces to verify information flow, improving code coverage. It also exposes dependencies, helping testers identify conflicts between multiple components or external systems.

Smoke testing

Smoke testing is done to ensure that the critical features of a build work correctly. While the scope of unit tests is to verify the smallest unit of logical code, smoke testing is done on a large scale. This helps identify major roadblocks that, if not resolved, can make further QA efforts meaningless. Smoke testing is also known as build-verification testing and is performed every time a new build is ready for release. If a set of smoke tests takes half a day, with automation, the same tests can be run in just a few minutes.

Use case scenario: For an e-commerce platform, adding an item to the shopping cart is a basic function, and this needs to be verified.

Importance of smoke testing:

  • When critical functionalities fail, stalling a build, further testing can be a waste of time and resources. These efforts can be curtailed to improve efficiency.
  • Eliminates risks that may crop up at a later stage when adding code to the existing build.
  • Resolving critical issues at the beginning of the sprint makes the software more robust.
  • It's a simple process that does not require many resources.

Sanity testing

Sanity testing, a subset of regression testing, is a comprehensive testing methodology that's performed to check if a newly added component functions as intended. Unlike regression tests, sanity tests are done to verify a single component, instead of the entire application.

Use case scenario: Let's say the existing modules of an e-commerce website are the login page, home page, user profile, and address book. The username criteria has been set to include alpha characters. But if the website allows the user to input alpha-numeric characters, this is a defect that needs to be fixed. Once fixed, the changes should be reflected in all the corresponding modules, such as the user profile and address book.

Importance of sanity testing:

  • Critical issues can be identified early in the development lifecycle.
  • The functioning of a specific component is tested to verify accurate behavior before deployment.
  • Running multiple rounds of regression tests can be avoided.
  • Sanity testing takes less time, as documentation is not required.

Interface testing

Every piece of software has multiple components that interact with each other through an interface. Verifying this interface to see if the data transfer works as intended is an integral part of testing. This involves testing the UI, API, and more. When it comes to interface testing, it's important to strike the right balance between manual and automated testing.

Use case scenario: Interface testing has many aspects. Below are some examples for an e-commerce platform:

  • A user must be able to navigate easily between the home page, product categories, profile page, etc. The end-to-end workflow should function as expected.
  • The interface should communicate seamlessly with the backend. If the quantity of watches available is displayed as 5 and the user adds one to their cart. The inventory should be updated to 4 watches.
  • The user interface should be aesthetically appealing and consistent across multiple screen sizes and orientations.
  • Product descriptions must be accurate.
  • The e-commerce application should be able to withstand heavy traffic.
  • Runtime errors need to be identified.
  • Potential security lapses and vulnerabilities need to be rooted out.

Importance of interface testing:

  • Testing the interface helps shorten the learning curve for the end user and improve the user experience.
  • Knowledge from interface testing helps increase the adoption of business applications.

Regression testing

With every small change in the code, a new round of testing needs to be performed. This is done to ensure that any new change in the code doesn't impact the existing codebase. This is known as regression testing. Regression tests are highly repetitive and should be automated to improve efficiency, cut costs, and save time.

Use case scenario: Lets take the address book module of an ecommerce platform. It has certain test scenarios:

  • Change billing address
  • Change shipping address
  • Add new address

Similarly, there will be other modules in the ecommerce platform, such as:

  • Login
  • Product search
  • Shopping cart
  • Checkout
  • Address book
  • Payment gateway integration
  • Order confirmation

Each of these modules will have a list of test scenarios, similar to the address book module.

In the event of adding a new module, or when any change is made to the codebase, the entire list of test cases under each of the 7 modules must be rerun.

Importance of regression testing:

  • The frequent iterations and feedback loop align regression testing with agile.
  • Continuous testing improves the stability of the software.
  • Any change in the software can be rapidly tested to ensure business operations aren't stalled.

Acceptance testing

The aim of acceptance testing is to replicate the end-user experience to verify if the final product has achieved the desired outcome. In automated acceptance testing, user interaction is simulated. Automated testing can remove human errors, biases, and inconsistencies, and save a lot of time. It also improves test coverage with predefined scripts, extensive logs, test reporting, and documentation.

Use case scenario: When a user hovers over the product, a quick view with the product description, available colors, sizes, and rating is a good-to-have feature for an e-commerce web application.

Importance of acceptance testing:

  • It helps understand if the product is living up to market standards.
  • Evaluates the final output against specifications.
  • The reliability of the product is checked before deployment.

Automated functional testing

Functional testing is the cornerstone of software development, as it performs a complete 360-degree quality check of the frontend and backend elements of software. Businesses these days are heavily reliant on their software and cannot afford the consequences of manual errors. In such scenarios, automated testing can be adopted to improve speed and accuracy.

Zoho QEngine is a feature-rich tool that offers the capability to test on multiple platforms simultaneously. The no-code recorder, low-code builder, and pro-code editor features of QEngine provide flexibility and efficiency. It also comes with extensive reporting capabilities that provide actionable insights. With Zoho QEngine, you can test on the cloud, a local agent, or in a hybrid environment, and the collaborative features are a great addition for your testing teams.