Catalog
method#Quality Assurance#Reliability#DevOps#Software Engineering

Functional Testing

A method to validate that software meets specified functional requirements by executing features and end-to-end scenarios.

Functional testing verifies that software meets specified functional requirements by exercising individual features and end-to-end scenarios.
Established
Medium

Classification

  • Medium
  • Technical
  • Design
  • Intermediate

Technical context

Continuous integration systems (e.g. Jenkins, GitHub Actions)Test frameworks and libraries (e.g. Selenium, JUnit)Issue trackers and test management tools

Principles & goals

Focus tests on specification and observable behavior.Automate repetitive test scope while retaining exploratory checks.Differentiate functional tests from implementation and performance tests.
Build
Team, Domain

Use cases & scenarios

Compromises

  • Flaky tests cause loss of trust in test suites.
  • Insufficient coverage can miss critical defects.
  • Tight coupling to concrete UI implementation increases maintenance costs.
  • Write maintainable, isolated automated tests with clear assertions.
  • Prioritize test cases by risk and customer value.
  • Use stable test data and environment isolation to reduce flakiness.

I/O & resources

  • Specifications and acceptance criteria
  • Build artifacts to be tested
  • Test data and test environments
  • Test logs and reports
  • Defect and ticket lists
  • Acceptance decision or release approval

Description

Functional testing verifies that software meets specified functional requirements by exercising individual features and end-to-end scenarios. It focuses on inputs, expected outputs and observable behavior without inspecting internal implementation. Typical techniques include manual exploratory testing, automated test suites using frameworks, and acceptance tests to prevent regressions and validate releases.

✔

  • Early validation of features against requirements.
  • Reduction of regressions through automated suites.
  • Improved acceptance confidence for stakeholders and product owners.

✖

  • Does not cover internal implementation errors.
  • Costly test data and environment setup for integration tests.
  • Automation requires initial development effort.

  • Test coverage (functional)

    Percentage of specified functions that are covered by tests.

  • Defect density after release

    Number of discovered defects per release relative to tested functionality.

  • Test suite runtime

    Time required to execute the complete functional test suite.

E-commerce checkout tests

Functional tests verify the entire purchase flow including discount logic and payment processing.

API functional check of a payment service

Automated tests check API endpoints for expected responses and error handling.

Form validation in customer portal

Manual and automated tests validate inputs, error messages and successful persistence.

1

Identify requirements and acceptance criteria

2

Derive and prioritize test cases and scenarios

3

Provision test environment and test data

4

Analyze automation potential and create test suites

5

Integrate tests into CI/CD and optimize runtimes

6

Evaluate results, track regressions and improve

⚠️ Technical debt & bottlenecks

  • Outdated test cases not adapted to code changes
  • Lack of modularization in test automation code
  • Insufficient test data management and versioning
Insufficient test data and data maskingUnstable test environmentsFlaky tests due to timing dependencies
  • Perform only functional tests and neglect integration tests.
  • Automated tests without assertions for critical flows.
  • Use test suites as blockers without risk-based differentiation.
  • Wrong prioritization leads to long release cycles.
  • Tight coupling to test data hinders reuse.
  • Unclear acceptance criteria lead to undefined test goals.
Ability to derive test cases from requirementsKnowledge of test automation and frameworksExperience with CI/CD integration of tests
Testability of componentsAvailability of stable test environmentsFast feedback via CI/CD
  • • Time pressure before releases limits test scope
  • • Access restrictions to production data
  • • Budget for test automation is limited