If you thought tests were over when you earned your diploma, think again. Any good software developer will let you in on a little secret: tests ensure programs run smoothly. And the testing pyramid tells you how to write those tests.
Whether you know it as the software testing pyramid or the test automation pyramid, the testing pyramid was designed to help structure the frequency and types of tests used when developing a program.
The test pyramid explained
Developed by Mike Cohn in his book “Succeeding with Agile,” the testing pyramid illustrates the optimal number and types of tests to use during software development. Let’s look closer.
How many layers does the testing pyramid have?
Typically, the testing pyramid has the following three layers:
Note: Sometimes people place static analysis as the base. That pyramid looks like this:
Do the layers of the pyramid overlap?
Yes, some layers naturally overlap—especially when integration tests cover functionality that could also be validated in end-to-end tests. Defining clear boundaries for each layer helps avoid duplicate testing and keeps your test suite efficient.
Unit testing
Unit tests are the most common tests. They are also the most specific tests: they check if a particular unit in the codebase is working correctly.
Definition
Unit tests test a single functionality and small units of code. They are fast to execute and help developers quickly spot and correct foundational errors.
Who performs unit tests?
Unit tests are typically written and executed by software developers, since they are responsible for verifying that each piece of their code functions correctly before it’s integrated with the rest of the application.
What to test
- Test the public interface of the class or function.
- Cover all meaningful code paths, including the happy path and edge cases.
- Create one test class per production class or module to keep tests organized and maintainable.
When to perform unit tests
- Run unit tests frequently during development, ideally as part of your local workflow.
- Test each unit of code immediately after it’s written, before integrating it with other components.
Unit testing examples
For unit testing, isolation is the key. Individual components or functions are each tested separately. Here are some examples:
- User authentication methods: How does the login system respond to incorrect passwords or usernames? Does the system require the correct credentials?
- Notification system: Does the system provide accurate alerts when errors occur?
Unit testing best practices
- Keep it simple (K.I.S.S.): Write straightforward tests that are easy to read and maintain.
- Test one scenario at a time: Each test should validate a single behavior or outcome to make failures easy to diagnose.
- Ensure tests are repeatable and scalable: Tests should run consistently with the same results and be easy to expand as the codebase grows.
Unit testing tools
Use these open-source tools to create strong unit tests:
- Unity: Unit testing for C, especially embedded software
- Mocha: JavaScript test framework running on Node.js
- NUnit: Unit testing framework for all .NET languages
- TestNG: Inspired by JUnit and NUnit, it’s a JavaScript testing framework.
- JUnit: Testing framework for JAVA and the JVM
Integration testing / Service testing
Now that you’ve laid a strong foundation with unit testing, continue with the next phase of integration (or service) testing. Unfortunately, there’s some debate within the software community as to what integration tests are.
Sometimes, this testing is also called:
- Integration tests
- Component tests
- Service tests
Definition
Integration tests verify how the different flavors work together. Integration testing checks the combination of the components. They ensure that the modules, services, and systems will all work together seamlessly.
What to test
- When you serialize or deserialize data, write a test to make sure your code completes its journey correctly.
- Write tests to verify that different modules, components, or functions interact with each other correctly.
Who performs integration tests?
Integration tests are typically executed by QA or specialized test engineers because they focus on verifying how different modules or services work together, rather than testing individual pieces of code.
When to perform integration testing
Integration testing is performed after individual components are developed and unit tested, but before the software is released, often as part of a CI/CD pipeline.
Integration test examples
Here are a few scenarios that demonstrate how integration testing works in practice:
- User permissions and data updates: When one user updates a record (e.g., changing their address in a healthcare portal), another user with the correct permissions can immediately view and interact with the updated information.
- E-commerce checkout flow: A customer logs in, adds an item to the cart, and completes payment. Integration testing verifies that the login service, cart module, and payment gateway all work together seamlessly.
- Microservices communication: In a banking app, the transaction service triggers an email service to send a receipt and updates the account balance service. Integration testing ensures that the services exchange data correctly.
- End-to-end API flow: When an API request is made to submit a form, the data is serialized, stored in the database, and triggers a confirmation email. Integration testing validates this entire workflow.
Integration tests vs unit tests
- Unit tests are small tests for specific components; integration tests see how different areas work together. Unit tests are simple, short, and sweet. Integration tests are longer and more complex.
Best practices for integration testing
- Focus on key system interactions
- Test in small groups
- Conduct positive and negative tests
- Automate integration testing
- Don’t mix unit testing and integration testing
- Make integration tests part of your CI/CD process
- Don’t wait; start as soon as possible
- Focus on key system interactions
- Mimic third-party services scenarios (using mock framework)
Integration testing tools
The following are some tools to help with integration testing:
- Ranorex: Provides a complete, end-to-end test automation solution for desktop, web, and mobile applications. It allows you to create integration tests that validate both the UI and backend services, and easily integrates into CI/CD pipelines.
- API testing frameworks: Tools like Postman or REST Assured can help validate service-level interactions and API responses during integration testing.
- Custom scripting with CI/CD integration: Teams often use Python, PowerShell, or other scripting languages combined with CI tools like Jenkins or Azure DevOps to trigger automated integration tests across environments.
End-to-end (E2E) / User experience (UI) tests
At the top of the testing pyramid are end-to-end (E2E) tests, which validate the application from the user’s perspective. These tests interact with the fully deployed application through its user interface to ensure the entire workflow functions as expected.
Definition
End-to-end testing puts the tester in the user’s shoes, validating the entire workflow to ensure a seamless experience. It checks that all integrated components work together correctly and helps catch any issues that could disrupt real-world usage.
What to test
When conducting end-to-end testing, you are checking:
- The app’s behavior
- The app’s layout
- The app’s usability
Who performs E2E tests?
Specialized QA teams typically handle E2E testing, ensuring that the full user workflow is thoroughly validated. Developers are usually less involved at this stage.
When to perform E2E tests
Run E2E tests after integration testing and before the product launch to confirm that all components work together seamlessly in a real-world environment.
E2E testing examples
The following are E2E testing examples:
- Collaboration features: Can team members work together on a project without running into bugs? Simulate different working situations.
- Buying a product: Simulate someone logging in, browsing, and purchasing a product.
End-to-end testing best practices
- Automate with codeless test automation
- Mimic real-user interactions
- Design realistic tests for the most critical scenarios
- Give your tests an order of importance
- Test from the user’s point of view
- Set up tests for off-peak times or before major updates
E2E testing tools
- TestRail: A comprehensive test management platform that helps you plan, track, and report on testing from definition to delivery.
- Ranorex: Provides full end-to-end test automation across desktop, web, and mobile applications. It’s ideal for validating complete user workflows and integrating seamlessly with CI/CD pipelines.
- Selenium: An open-source framework for automating browser-based testing.
- TestRigor: An AI-based tool that converts plain English test instructions into automated tests.
Test pyramid benefits
The testing pyramid offers multiple advantages for QA and development teams:
- Balanced approach to testing: It layers numerous short unit tests at the base with fewer, longer E2E tests at the top, creating a time- and cost-efficient structure.
- Simplifies Agile testing: A clear framework removes guesswork about which tests to prioritize in fast-paced Agile environments.
- Early bug detection: Extensive unit testing at the start helps identify and fix issues early, reducing downstream defects.
- Improved QA focus: With most bugs caught early, QA teams can spend more time on refining quality rather than firefighting.
- Testing efficiency and faster feedback: Running many quick, lower-level tests provides immediate insights after each code update, avoiding bottlenecks from slower E2E tests.
- Comprehensive test coverage: It ensures everything from individual components to full system workflows is validated.
- Optimized resource allocation and cost savings
Emphasizing fast, low-cost unit tests prevents overreliance on expensive and time-consuming E2E tests.
The test pyramid’s shortcomings and challenges
The testing pyramid has challenges, such as:
- Naming convention: If test names aren’t clear, it can be hard to tell which layer of the pyramid they belong to—unit, integration, or end-to-end. This makes it harder to maintain the proper test balance and can lead to misclassified tests, which skews coverage and slows down debugging.
- Too simplistic: The oversimplification of all the testing areas might be misleading.
- Test maintenance: Code changes and system updates can create false positives or false negatives in automated integration and E2E tests.
- Unreliable tests: Network instability, timeouts, or third-party service dependencies can lead to inconsistent test results.
- Test environment setup: Simulating a real-life environment can be difficult.
- Execution time: Bottlenecks can occur because integration and E2E tests run slower than unit tests.
- Integration testing complexity: As the system grows, it becomes increasingly difficult to cover all areas, all interactions, and all combinations. Knowing which combinations to test without having overlap can be tricky.
What makes a good test structure?
To create a good test structure, remember, “Arrange, Act, Assert.” According to Martin Fowler, this means:
- Arrange: arrange and organize your test data
- Act: act the method call
- Assert: assert you have the results you needed
How to integrate the testing pyramid into development workflows
Similar to the pyramids in Egypt, the testing pyramid needs to be strategically planned before it is built.
- Begin with unit testing: Developers should write code and unit tests simultaneously, ideally using test-driven development (TDD). Automate these tests with tools like JUnit or TestNG to ensure fast, reliable feedback.
- Move to integration testing: Once unit tests are in place, create integration tests to verify that modules, services, and components work together as expected.
- Take a strategic approach to E2E testing: Focus end-to-end testing on the most critical and common user flows since these tests are slower and more resource-intensive.
- Review and adjust continuously: Testing is ongoing. Regularly evaluate test efficiency, reduce flakiness, and add or adjust tests as the system evolves.
- Leverage automation tools: Use automation tools to execute more tests with less manual effort and ensure consistent results across builds.
- Encourage collaboration: Involve developers, QA engineers, and stakeholders to share insights, streamline processes, and maintain system quality effectively.
Test pyramid tips
- Stick to the pyramid shape: Focus on having many small, fast tests at the bottom and only a few large, slow tests at the top.
- Define your own test layers: Because test names vary across the industry, establish clear names and definitions for your organization’s test layers.
- Prioritize by risk: Determine which areas of your application are most critical and test them first.
- Write more tests at the bottom, fewer at the top: This is the single most important takeaway—opt for broad unit test coverage and minimal E2E tests.
- Keep test code clean: Follow best practices like Fowler’s “Arrange, Act, Assert” pattern to make tests easier to maintain.
- Integrate tests into the pipeline: Automating tests in your CI/CD process accelerates feedback and improves release speed.
- Verify real-world user scenarios: Design tests that reflect actual usage to catch issues that matter most to end users.
- Avoid duplication: If multiple tests cover the same behavior, consolidate and push the test down the pyramid whenever possible.
- Include exploratory testing: Manual exploration helps uncover edge cases or unexpected bugs that automated tests might miss.
Strengthen testing quality with TestRail
You can strengthen and improve your testing with TestRail—a centralized test management platform that will help you with every stage of the testing pyramid.
So, what are you waiting for? Sign up for a free 30-day trial with TestRail and see how much time you save on testing.
About the author
Jorge Spratley is a Lead Product Manager at TestRail with nearly a decade of experience in the B2B tech space. His career spans industries including retail, eCommerce, EdTech, and Fintech. With a background in Psychology, Business Communication, and Computer Science, and global experience across Portugal, the UK, and Australia, Jorge brings a diverse perspective to product innovation and QA solutions.
