System Testing vs End-to-End Testing Explained With Examples
Confusing system testing with end-to-end (E2E) testing can lead to duplicate work, overlooked defects, and delayed releases. While both are part of the software testing life cycle, they differ in scope, objectives, and execution.
We explain each with a side-by-side comparison and examples to help QA teams choose the right approach for their project stage.
System testing vs end-to-end testing
Feature | End-to-end testing | System testing |
|---|---|---|
Objective | Validate the entire user journey and system behavior across multiple components and integrations. | Ensure that each component of the system works correctly within the complete environment. |
Scope | Broad; involves multiple systems, subsystems, and external integrations. | Limited to the internal components of a single system without focusing on external systems. |
Focus | User interactions, workflows, and data flow across multiple systems. | System functionality, internal interfaces, and behavior against requirements. |
Test coverage | Comprehensive, covering the full process from start to end. | Covers specific functionalities and features as defined by requirements. |
Execution level | High-level, mimicking real-world usage. | Intermediate-level, focused on internal system behavior. |
Complexity | High, due to involvement of multiple systems and dependencies. | Moderate, limited to internal systems and interfaces. |
Figure 1: The place of system & end-to-end testing in SDLC.
What is system testing?
System testing verifies a fully integrated and finished piece of software. Through system testing, a QA team assesses how the various application components interact with one another in a complete, integrated system or application.
System testing falls under black box testing since it examines how the software functions externally from the viewpoint of the user.
In system testing, testers:
- Check for desired outputs by thoroughly checking each input in the application.
- Evaluate the user’s experience of the application and the user interface (UI).
- Examine all application components to ensure they work thoroughly and uniformly as a whole.
When is system testing performed?
Testers often carry out system testing after integration testing and before acceptance testing. See Figure 1 for the complete SDLC timeline.
What are the benefits of system testing?
- Identifying potential problems: System testing can be used to determine program weaknesses and pinpoint areas in need of repair.
- Ensuring compliance: Testers can determine whether the software meets the program’s criteria and objectives.
- Complete testing: System testing tests the entire piece of hardware or software, allowing testers to quickly find any flaws or problems that may have slipped through integration and unit testing.
- Reducing reliance on hard-to-hire technical skills: Testers don’t need additional programming expertise to perform system testing.
- Accurate testing: The testing environment is similar to the production or business setting.
How is system testing done?
Prepare a testing plan
System testing begins with creating a detailed testing plan that outlines objectives, scope, success criteria, and responsibilities. This document ensures all QA team members follow the same approach.
For example, in a healthcare management application, the plan might define goals such as verifying patient data accuracy across modules, testing user role restrictions, and ensuring compliance with HIPAA requirements.
Set up the testing environment
The testing environment should replicate the production environment as closely as possible, including servers, databases, network settings, and configurations. This allows for accurate validation of system behavior.
For instance, in an ERP system, setting up the environment might involve configuring modules for inventory, sales, and finance, along with the same database structure used in production.
Write test cases
Develop specific test cases for each feature or functionality in the application. These should cover normal, edge, and error scenarios to ensure robust validation.
For example, in an online banking platform, test cases might include checking balance updates after a transfer, validating incorrect login attempts, and confirming interest calculations on savings accounts.
Execute testing protocols
Run the prepared test cases systematically, using both manual and automated testing where applicable. Ensure each case is executed in the defined sequence for consistent results.
For instance, in a university enrollment system, execution could involve creating a student profile, enrolling in courses, and verifying that the tuition fee calculation is correct.
Report defects
Document any issues or unexpected behavior found during execution, including steps to reproduce, screenshots, and severity level. This helps developers address problems efficiently.
For example, in a travel booking application, a defect might involve incorrect currency conversion when displaying total booking costs.
Perform regression testing
After fixes are applied, run regression tests to confirm that changes have not introduced new defects or broken existing functionality.
For instance, in a retail POS system, after fixing a discount calculation bug, regression testing might confirm that the payment process, receipt generation, and inventory update still work correctly.
What is end-to-end (E2E) testing?
End-to-end (E2E), also known as chain testing, is a methodology for ensuring that software is functioning as intended and that data flow is preserved for all user tasks and processes.
End-to-end testing aims to simulate a complete production environment by thoroughly testing the entire software for dependencies, data integrity, and communication with other systems, interfaces, and databases.
It is also a key testing practice when a product is required to function collectively with the other systems in various environments. In such scenarios, validation of data processing from upstream and downstream systems is required to maintain accurate interaction across different platforms & environments.
When is end-to-end (E2E) performed?
End-to-end (E2E) testing is usually performed after system testing. It is especially useful to identify system dependencies, considering that it tests both the software system and the connected systems. See Figure 1 for the complete SDLC timeline.
What are the benefits of end-to-end (E2E) testing?
End-to-end testing can provide the following benefits:
- Increased test coverage: It adds more thorough test cases than other testing techniques like unit and functional testing, which helps teams increase their test coverage.
- Reducing overall cost: Decreases the time needed to test software, thereby lowering the overall cost of building and maintaining software.
- Determining priorities: End-to-end testing assists managers in setting priorities for tasks in the development backlog by determining the significance of a workflow to the user in the real world.
How is E2E testing done?
Define test scenarios
E2E testing begins with defining critical user journeys or workflows that need to be validated, such as user registration, login, checkout processes, or data input and retrieval. These workflows represent the primary ways users interact with the application.
For example, in an e-commerce application, a critical scenario might be verifying the checkout flow from adding a product to the cart to completing a payment.
Set up the test environment
To accurately test an application’s entire flow, the testing environment should mirror the production setup as closely as possible. This may include configuring servers, databases, third-party services, and any other systems or network configurations needed to support the full application.
For instance, in a banking application, setting up the environment might involve configuring test databases, network connections, and external services like payment gateways to simulate the production environment.
Prepare test data
E2E tests often require specific data to simulate real-world scenarios. This data can be manually created, imported, or generated through scripts. It should represent realistic use cases that the application will encounter in production.
For example, for a social media platform, sample user profiles, posts, and interactions might be created to represent real user data and actions.
Write test scripts
Test scripts are written to automate the actions users would take within the application. Commonly, these scripts are created using E2E testing frameworks like Selenium, Cypress, or Playwright, which provide tools for interacting with the user interface, making API requests, and checking data consistency.
For instance, in a ride-hailing app, automated scripts might include actions like entering a pickup location, selecting a destination, and verifying that a driver is assigned correctly.
Execute tests
Once the scripts are ready, they are executed in the testing environment. The automated scripts perform each action as a user would, clicking buttons, filling forms, verifying outputs, and checking that data flows correctly between systems.
For example, in a travel booking app, this could involve running scripts that simulate searching for flights, booking tickets, and checking confirmation emails in the test environment.
Validate results
The final step involves validating the outcomes of each test case against the expected results. This includes checking for correct visual elements, functional responses, data accuracy, and proper integration with third-party services. Any discrepancies are reported as issues.
For example, in a messaging app, validation might involve checking that messages sent by one user appear correctly for the recipient and that notifications are triggered as expected.
Debugging and re-running tests
If errors or failures are identified, the code or configuration is adjusted, and the tests are re-run to ensure the issues are resolved. This iteration helps improve the reliability of the application before it’s released to users.
For instance, if a checkout test fails in an online store due to a payment error, the script and payment service would be reviewed, updated, and re-run to confirm the fix.
Methods of software testing
To understand the positioning of system testing and end-to-end testing, we can look at the three types of software testing.
Black-box
Black-box testing is a software testing method that evaluates the functionality of an application. Knowledge of the internal working structures is not required for this type of testing. It is based on software requirements and primarily concentrates on the input and output of software programs.
White-box
White-box testing examines an application’s internal components or mechanisms in contrast to testing its functionality. Designing test cases for white-box testing involves viewing the system from within.1 Thus, knowledge of the internal working structure is required for this type of testing. The tester selects inputs to test various code paths and identifies expected results.
Gray-box
Gray box testing is a combination of white box and black box testing. With this method, testers approach the software from an end-user perspective while having partial knowledge of the code internals.
To better understand end-to-end testing, check our article, “7 End-to-End Testing Best Practices”
Reference Links
Cem's work has been cited by leading global publications including Business Insider, Forbes, Washington Post, global firms like Deloitte, HPE and NGOs like World Economic Forum and supranational organizations like European Commission. You can see more reputable companies and resources that referenced AIMultiple.
Throughout his career, Cem served as a tech consultant, tech buyer and tech entrepreneur. He advised enterprises on their technology decisions at McKinsey & Company and Altman Solon for more than a decade. He also published a McKinsey report on digitalization.
He led technology strategy and procurement of a telco while reporting to the CEO. He has also led commercial growth of deep tech company Hypatos that reached a 7 digit annual recurring revenue and a 9 digit valuation from 0 within 2 years. Cem's work in Hypatos was covered by leading technology publications like TechCrunch and Business Insider.
Cem regularly speaks at international technology conferences. He graduated from Bogazici University as a computer engineer and holds an MBA from Columbia Business School.
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