Introduction

A software application goes through multiple testing stages before it reaches users. Two stages that often create confusion are integration testing and system testing. Both belong to common types of software testing, and both help teams find issues before the product reaches users.

System testing checks the whole application as one unit, while integration testing checks how specific parts of the application work when combined.

This blog explains the difference between both in a straightforward way showing how they complement each other.

What Integration Testing Means

Integration testing checks whether one feature can correctly use another feature it depends on. Whenever a flow moves from one feature to the next or one action triggers a related process, integration testing makes sure this connection works as intended. It focuses on linked flows such as login moving to the dashboard, checkout using the payment service, or search pulling the right results.

What Integration Testing Usually Covers

Connections Between Features

Integration testing checks how features link together, such as login moving to the dashboard or checkout leading to payment. These links often break even when individual features work fine.

Example: In an order placement flow, completing the checkout step should take the user to the order confirmation page without losing the selected items, address, or payment details..

Data Shared Across Features

It verifies the data passed between features, including user inputs, IDs and parameters. Incorrect or missing data is a common source of issues that surface later in the flow.

Example: The order ID, selected items, and user details created during checkout must be passed correctly to confirmation and order history.

Shared Resources in the App

Different features often rely on the same database records, cache entries, configuration values, or session data. When these shared resources are updated or accessed at the same time, conflicts can appear even if the features never interact directly. Integration testing checks these indirect dependencies to confirm that the overall flow stays consistent when several features use the same underlying resources.

Example: Inventory data updated after an order is placed should remain consistent across checkout, availability checks, and order history.

Multi-Step Functional Flows

Integration testing checks flows that require steps to run in a specific order, such as bookings, cart movement or profile updates. If one step does not pass control correctly, the entire flow can fail.

Example: Payment should be processed only after order validation succeeds, and order confirmation should appear only after payment completion.  

What System Testing Means

System testing checks the complete application. At this point, all modules are connected, and the product behaves like a finished system. The purpose is to validate the end-to-end behaviour, both functional and non-functional.

Unlike integration testing, which focuses on internal connections, system testing examines how the entire product behaves for real users.

What System Testing Usually Covers

Full User Journeys

System testing reviews complete user flows such as user registration, login, navigation, and task completion. These full-flow checks help reveal issues that appear only when a user moves through the entire sequence, not when features are viewed in isolation.

Example: A user should be able to move from browsing items to checkout, payment, and order confirmation without hitting broken screens or dead ends.

End-to-End Data Movement

System testing observes how data is stored, updated, retrieved, and displayed across the whole application. This catches problems that surface only when information travels through multiple features instead of stopping at a single step.

Example: Order details created during checkout should appear correctly in confirmation screens, order history, and follow-up actions like tracking.

Combined Behaviour of All Features

System testing evaluates how all features behave when the entire application runs together. Running everything at once helps expose issues caused by shared logic, shared state, or interactions that lower-level tests miss.

Example: Checkout, payment, inventory updates, notifications, and order history should all behave consistently when an order is placed.

UI and Interaction Behaviour

System testing includes how screens load, how elements respond, and how users interact with different parts of the interface. These interactions matter because slow or inconsistent UI behaviour can break the user experience even if the backend is correct.

Example: Buttons, loaders, and confirmations during order placement should respond correctly without freezing, duplicate actions, or skipped states.

Performance Under Expected Conditions

System testing reviews how the full application responds during typical usage patterns. This step highlights delays or instability that only appear when real workflows and real load come together.

Example: Order placement should complete within acceptable time limits even when multiple users are placing orders at the same time.

Error Handling Across the Application

System testing covers how the application responds to invalid inputs, failed operations, or missing information during complete flows. This helps reveal gaps that don’t appear in controlled or isolated tests.

Example: If payment fails or inventory runs out mid-flow, the user should see a clear error and a safe recovery path instead of a broken state.

Key Differences at a Glance

Also Read - What Is Reliability Testing and Why Does It Matter in Software Quality

How Integration Testing and System Testing Work Together With HeadSpin

Real Device Testing Across the Globe

HeadSpin allows teams to design, automate, and run both integration and system-level scenarios on real devices across more than 50 global locations and real networks.

For integration testing, teams can validate how connected features behave together by running defined integration flows, such as API calls, data updates, and UI confirmations, on real devices and triggering them through CI pipelines.

For system testing, end-to-end scenarios can be designed and automated as full end-to-end scenarios across different device models, OS versions, browsers, geographies, and network conditions. This helps teams confirm that the complete system behaves as expected across real ecosystem combinations instead of limited lab setups.

Performance Tracking With 130+ KPIs

HeadSpin tracks more than 130 performance KPIs across network behavior, device performance, and app responsiveness. These KPIs support non-functional performance checks during integration and system testing through performance monitoring and network condition simulation, allowing teams to assess response time, resource usage, and reliability while running the same integration and system test scenarios..

Session Recordings and Shareable Reports

Every session is recorded so teams can replay failures, reproduce issues, and confirm fixes. Shareable reports help developers and QA work with the same evidence during both integration and system testing.

Final Summary

Teams can treat integration testing and system testing as two checkpoints that guide how they shape the rest of their QA work. A practical way forward is to treat integration tests as a continuous activity throughout development rather than a one-time phase. System testing can then focus on real usage, performance, and behaviour rather than fixing basic interaction problems. 

See how HeadSpin helps teams test modules, APIs, and full workflows in one place. Connect with Us!

FAQs

Q1. When should Integration Testing be performed in the SDLC? 

Ans: Integration testing should begin once individual components or features have passed unit testing and are ready to work together. It usually runs after development teams complete a stable build of connected functions and before system testing begins.

Q2. What tools are commonly used for integration and system testing?

Ans: Integration tests often rely on API testing tools and component-level frameworks. System tests usually depend on real devices, UI automation tools, and environments that mirror production.

Q3. How do integration issues affect system testing?

Ans: Weak integration testing leads to system tests failing for reasons unrelated to full workflows. This increases noise, delays debugging, and forces system-level testers to trace problems back to basic module interactions.