Introduction to Functional Testing


Functional Testing is a type of software testing which is performed to validate the basic functionality of the Software Application against functional requirements. Software is developed based on business requirement and Functional Testing helps and assures that Software developed is as per the business requirements.

Functional testing comes under black-box testing as functional tester does not bother about how the code is written or conducts code review to validate the code, instead, he executes the software and provide inputs based on business and functional requirement and validates against his expected result to certify the Application.

Functional Testing can be carried out for any software irrespective of Web Application, desktop application, web service or a stored procedure. Be it any type of Technology, the objective is to validate the functionality of the system under test is as per the business / functional requirement.

Introduction to Functional Testing

Why Functional Testing:

Why Functional Testing leads to a question of why testing?

Testing is done to ensure that the application works as expected. When an application is delivered without testing, then there is no assurance/guarantee that the application will function as expected. More than 60% of testing efforts go to Functional Testing effort. Remaining efforts would be a part of Non-Functional Testing like Performance, usability, security, etc.

Without Functional Testing we cannot conclude software does the operation as expected and hence Functional Testing is as important as software being developed by the development team.

Aspects of Functional Testing

Below are the key aspects of Functional Testing:

1. Testing based on Functional Requirement

2. Testing based on Business Process

Testing based on Functional Requirement

This Testing is based on the nature of the application functionality. Whenever a build is provided based on User stories / Functional Specification / Business Requirement document, we carry out various types of testing to prove it function as expected.

Before delivering the Application to Functional Testing team, developers do testing and it is called Unit Testing. Once developers complete the Unit Testing Application build is delivered to the testing team for Functional Testing.

Before we conduct a thorough Functional Testing we perform Smoke and Sanity Testing to ensure that build is stable and can be carried out for further testing. When a build is failed in smoke and sanity, that means the build has a serious flaw and developer has to further work on it.

Once Smoke and Sanity Testing is passed, Integration, System Testing and System Integration Testing is performed to certify the Application under test.

Testing based on the Business process:

When we say Business process from Functional Testing point of view, it is the End to End flow of business-critical functionality. Example) if an Application deals with Payment processing, then the business process would be testing the Payment setup until payment initiation until successful / exception criteria.

We could define a critical end to end business process considering positive and negative flow and testing these critical business areas. From this aspect, we could also perform risk-based testing based on the testing timeline and the number of business process areas.

Entry and Exit criteria of Functional Testing

Below are the key Entry criteria for Functional Testing:

Requirements must be fully frozen with clearly defined expected outcome (Requirements could come in the form of Business Requirement / Functional Specification document or User Stories)

Development should be completed

Build must be unit tested and completely signed off by the development team

Test Strategy and Test plan should be completed and should be signed off by stakeholders

Test data should be available for execution

Below are the key Exit criteria for Functional Testing:

Test cases should be prepared with complete coverage on requirements

Test cases should be reviewed and signed off by the Business team

Test cases must be executed and Severeity1 and 2 defects should be closed by Testing team

Functional Testing Strategies:

Before performing functional testing, below pointers/strategy would help to manage the test effectively:

Validate if the requirements are clear

1. To test effectively requirements should be clear with the clearly defined input and output criteria’s

2. If the requirements are not clear, enter into series of discussion with Business team, development team and project stakeholders beforehand and take steps to crystallize the requirement.

3. Even after series of discussion, if requirements are not clear come up with the In-scope and out of scope and keep requirements whichever are not clear in out of scope.

4. Raise a project-level risk and get into agreement with project stakeholders.

Assess and come up with proper Functional Plan

1. Based on the requirement clarity and project scope come up with Functional Test plan covering the scope of testing, type of testing to be conducted, Test schedule, resource requirement, risk management procedure, etc

2. Once the Functional Test plan is prepared, get it signed off from project stakeholders

Identify the Test Schedule and Execution Timeline

1. Based on the project plan, identify time allotted for Testing phase

2. Calculate the execution timeline

3. Come up with Risk-based Testing approach for better functional coverage

4. If the timeline is less, execute P1, P2 Test cases and get into agreement with Stakeholders

Resource fulfillment and Automation assessment

1. Based on the project schedule and Test schedule, assess and do feasibility of Automation and validate the benefits expected out of automation

2. Identify the right resource requirement if automation can be implemented

Proper Defect Management

1. Assign proper defect Manager / Coordinator for conducting defect triage calls

2. Escalate for Sev1 and Sev2 priority fixing with development counterparts

3. Extend timelines or come up with alternate plans based on Environment/delay in defect fixes

4. Assign to testers based on defect fix by the development team

5. Review of defect retesting and closure

Proper Test Completion Report

1. When Functional Testing is completed, Test Completion report has to be prepared

2. While preparing Completion report, ensure in-scope and out of scope is declared properly

3. Update inference from Functional Testing and any defects are open/deferred update it properly in the closure report

4. Update what went well, what not went well with a reason along with improvement areas as well to be updated

Key Metrics that we report on Functional Testing

Functional Testing metrics can be classified based on the Test Phases:

Test Design Metrics:

Total Test Coverage

Automation Coverage

Test Design productivity (Manual and Automation)

Test Execution Metrics:

Test Execution productivity (Manual and Automation)

Test Execution Coverage

Error Discovery Rate

Test cases Passed / Failed / Blocked / Deferred

Defect Metrics:

Defect Leakage

Defect Removal Efficiency

Defect Density

Defect Fix Rate

Key Business Outcome

Present the Functional Testing Outcome post every release during retrospection/release closure discussion.

Invite key stakeholders and provide an update to key parties on overall Functional Testing outcome and benefits through Functional Testing activity. Since the QA team is much closer to the Business team in-terms of business requirements understanding, present how much of defects have been raised with criticality and how many defects converted to release / functional enhancement will be the key thing to be discussed. This will be an interesting story to Business team.


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