Compatibility Test (Compatibility Testing)

Compatibility testing is a type of non-functional testing designed to determine whether software operates consistently and without errors across different hardware and software environments, browsers, devices, and network configurations. It enables early detection of bugs that compromise the user experience across various environment combinations, thereby enhancing product quality.

This testing process typically encompasses the following environments:

• Operating systems (Windows, macOS, Linuxetc.)
• Web browsers (Chrome, Firefox, Safari, Edge etc.)
• Hardware configurations (RAM, CPU, graphics card etc.)
• Mobile platforms (Android, iOS)
• Network environments (Wi-Fi, 4G, 5G, different bandwidths)

Compatibility testing emerged as a critical practice during periods when software development processes became increasingly complex and the diversity of platforms and devices expanded. Initially, it was driven by the need for desktop software to function reliably across different hardware and operating systems. However, for many years this testing type remained overshadowed by functional testing and was not systematically treated as a process designed to uncover issues directly impacting user experience.

With the rise of web-based applications, differences among browsers and variations in HTML/CSS interpretation caused software to behave inconsistently across environments. During this period, developers were compelled to test their applications on different browsers such as Internet Explorer, Netscape, and Mozilla. However, these tests were typically conducted manually and inconsistently.

The global proliferation of Android and iOS operating systems created a need to test mobile application user interfaces across varying screen sizes, processor architectures, and OS versions. By 2017, Android’s market share in the mobile sector reached 85.9%, further underscoring the necessity of compatibility testing.

During this time, developers realized that ensuring an application worked on just one device was no longer sufficient; there was a growing need to develop applications compatible with thousands of devices and dozens of OS versions. This led to the increasing adoption of test automation concepts, with approaches such as GUI Rippling and Model-Based Testing (MBT) gaining prominence.

Manual testing of the vast array of devices and environments became impractical, prompting the development of automated compatibility testing tools. These tools include:

• Web-based tools such as BrowserStack, LambdaTest, and TestingBot that enable testing across different browsers and devices through virtualization.
• Academic projects like SlumDroid and GUIAnalyzer that have enabled model-based testing systems for Android applications.
• The TriTest Framework, which integrates compatibility testing with functionality and performance testing.
• In industrial control systems, software and hardware compatibility can now be tested using Siemens TIA Portal’s Openness API.

Today, compatibility testing is no longer limited to verifying whether software functions correctly in a given environment. It is now supported by quantitative criteria such as the selection of high-error-detection-capacity environments. Mathematical metrics like Environment Sensitivity Measure (ESM) allow testers to determine which environments are most valuable for testing. This approach has enabled software testing to become systematic and data-driven rather than intuitive.

In modern software development processes, where multi-platform and multi-layered systems are widespread, compatibility testing is one of the most critical test types for directly influencing user experience. It has a broad range of applications in verifying that software operates stably, error-free, and as expected across various combinations of hardware, software, networks, browsers, and devices.

Below are the primary application areas of compatibility testing explained in detail:

Due to differences in how various web browsers interpret HTML, CSS, and JavaScript, web applications may behave differently across environments. Compatibility testing addresses these issues by helping prevent:

• Clickability of buttons and links
• Functionality and data submission of forms
• Page layout, alignment, and font issues
• Browser-specific CSS/JavaScript errors

Tools used: BrowserStack, LambdaTest, CrossBrowserTesting

Mobile applications are used across a wide variety of devices and OS versions. Particularly within the Android ecosystem, manufacturer-specific UI layers, hardware differences, and version fragmentation can cause the same application to behave differently on different devices.

Compatibility testing monitors these variations:

• UI distortions caused by screen resolution and DPI differences
• Operating system version differences (e.g., Android 9 vs Android 13)
• Performance and battery consumption across different device models

Comprehensive testing strategy: Model-based or GUI ripper systems such as SlumDroid, TriTest, and Responsinator are employed.

Compatibility testing for desktop software involves testing across different operating systems, processor architectures (x86, x64, ARM), driver compatibility, and hardware parameters such as graphics cards.

Key areas of verification include:

• Application functionality across different Windows, macOS, and Linux versions
• Compatibility with graphics drivers and rendering engines
• Application behavior under RAM/CPU usage limits

This testing is particularly critical for graphically intensive applications, 3D rendering engines, games, and engineering software.

In industrial control systems (e.g., PLCs), compatibility between software and hardware components is vital for the safety and continuity of production processes.

Example compatibility test scenarios include:

• Whether a newly loaded control software can operate with the existing hardware topology
• Whether the device functions correctly after software installation (e.g., absence of an HMI device)
• Whether software and hardware remain synchronized after hardware restart

Siemens’ TIA Portal and Openness API architecture enable test automation in these processes.

In environments where software exchanges data with other systems, compatibility testing ensures integrated systems operate coherently.

Particularly in RESTful APIs, the following are tested:

• Correct processing of data types from different clients
• Control of backward compatibility issues during version transitions
• Compatibility of formats, encoding, and authentication protocols

IoT devices and embedded systems typically have limited processing power, memory, and network connectivity. Therefore, the application’s behavior in these constrained environments must be carefully tested:

• Operation with different firmware versions
• Compatibility with sensors and hardware drivers
• System behavior during connection interruptions

Compatibility testing enhances the stability of IoT solutions.

Application behavior under varying network speeds, connection instability, and layers such as VPNs is tested:

• Performance under 3G, 4G, 5G, and Wi-Fi scenarios
• Application response under packet loss and latency scenarios
• Effects of proxies and firewalls

Such tests are especially critical for video conferencing, VoIP, and live streaming applications.

The compatibility of text length, text direction (LTR/RTL), and date/time/currency formats across different languages is tested. Example: A button label that fits in English may overflow in German.

Compatibility testing is a planned and systematic process for evaluating whether software operates stably and as expected across different platforms, devices, networks, hardware, and browsers. While this process varies according to test strategy, environment diversity, and tools used, below is a step-by-step description of a general, academically grounded compatibility testing process.

As with any testing process, compatibility testing begins with developing a test plan.

In this phase:

• Target platforms (Windows, macOS, Linux; Android, iOS etc.)
• Browsers and versions (Chrome 120, Firefox ESR, Safari 17 etc.)
• Device types (tablet, phone, desktop)
• Network scenarios (4G, Wi-Fi, low bandwidth etc.)
• Hardware variations (RAM, CPU, GPU, HMI etc.) are defined.

This plan clarifies the scope of testing, prioritized scenarios, and the timing of each test.

• Use of Physical Devices: If testing is performed on real devices, these devices must be physically acquired. While this yields more accurate results, it is time-consuming and costly.
• Virtualization and Cloud Environments: Tools such as BrowserStack, LambdaTest, and SauceLabs enable simulation of various device and browser combinations in virtual environments.
• In Industrial Environments: In industrial control systems, compatibility between PLC hardware and software is tested using Siemens’ TIA Portal and Openness API. Realistic test environments are created using Software-in-the-Loop (SiL) and Hardware-in-the-Loop (HiL) strategies.

User scenarios to be tested in each target environment are defined. Examples:

Model-based testing tools (e.g., GUIAnalyzer, TriTest) can automatically generate test scenarios by scanning GUI elements during this phase.

Methods:

• Manual Testing: Simulates real user behavior and is especially important for detecting UI distortions.
• Automated Testing: Test scenarios are scripted and executed continuously and repeatably. Tools such as Selenium and Appium are commonly used.

In industrial systems:

• Tests are automatically initiated via an I-PC, verifying the match between PLC software and hardware.
• Target and current states are compared using XML/AML files used in the software.

Compatibility testing often reveals the following types of defects:

• Misaligned UI elements
• Corrupted fonts or colors
• Browser-specific JavaScript errors
• Buttons not functioning on specific devices
• API integration issues or timeouts
• Insufficient PLC configuration (e.g., undefined HMI device)

Detected defects must be reported in detail, clearly specifying the tested environment, version, and scenario.

Identified incompatibilities are shared with the software development team. After fixes are implemented, retesting is performed on the same environments. This step is critical to confirm that defects have been fully resolved.

An iterative model is applied in compatibility testing: Defect → Fix → Retest.

Each environment has a different capacity for detecting errors. The “Environment Sensitivity Measure (ESM)” method identifies environments more prone to uncovering test failures.

For example:

• Firefox 2.0.0.12 on Linux detected 96.3% of test failures.
• Such environments are designated as “priority test environments,” enabling optimized test sequences.

This makes the testing process more efficient by directing resources to the most critical environments.

In modern software processes, compatibility tests are integrated into CI/CD pipelines and executed automatically after every build. This enables immediate detection of potential incompatibilities after each update.

Since compatibility testing evaluates whether software operates consistently under different conditions, it is subdivided into various types based on its purpose and scope. These types vary according to the platform, version, hardware, network environment, and software component being tested. Below are the most common types of compatibility testing:

This type determines whether software functions correctly with various software components. Software compatibility testing identifies issues arising from interactions between the application and other software systems (databases, operating systems, libraries).

Tested environments:

• Operating systems (Windows, macOS, Linux)
• Databases (MySQL, PostgreSQL, Oracle)
• Third-party software (MS Office, browser extensions)

Example issue:

• A document creation application failing to integrate with the Outlook email client

This test type is particularly critical for API compatibility and service-based software integration.

This tests how software performs across different hardware configurations. This type is especially important for embedded systems, graphically intensive applications, and industrial control systems.

Tested components:

• RAM, processor (32-bit, 64-bit)
• Graphics card, sound card
• Embedded system microcontrollers
• Field equipment such as HMI and PLC

Industrial example:

• A newly loaded software on a PLC via Siemens TIA Portal is tested for compatibility with existing I/O modules.

This test determines how well a software application works with older or newer versions. It has two main subtypes:

• Backward Compatibility: The newly developed software is expected to function seamlessly with older system versions or hardware. Example: A mobile application still working on Android 9.0.

• Forward Compatibility: An older software version is evaluated for its ability to run on future operating systems or hardware. Example: An old game launching successfully on Windows 11.

Methods such as TriTest Framework and Environment Sensitivity Measure (ESM) can be applied to this test type.

This type examines how web-based applications perform across different web browsers.

Tested browsers:

• Chrome, Firefox, Safari, Edge, Opera
• Browser versions (e.g., Chrome 100 vs Chrome 120)

Tested elements:

• UI alignment, CSS loading
• Execution of JavaScript events
• Page load times

Performed using tools such as Responsinator and BrowserStack. These tests are especially important for responsive design validation.

This verifies whether an application functions identically across different physical devices (phones, tablets, desktops, IoT devices).

Factors considered:

• Screen size and resolution
• Processor type
• Availability of hardware resources

Example:

• A mobile game works correctly on an iPhone 13 but crashes on a Samsung Galaxy A50

This test type is critical for mobile application developers.

This tests how software performs under different network conditions and connection types.

Parameters considered:

• 3G, 4G, 5G, Wi-Fi, Ethernet
• Slow connections, high latency
• VPN, Proxy, Firewall environments

Example test:

• Whether a video conferencing application maintains video quality under low bandwidth

This type of compatibility testing is vital for real-time applications (VoIP, live streaming, cloud systems).

This evaluates whether an application functions correctly across different mobile operating systems and versions. It is especially important due to the diversity among Android devices.

Tested elements:

• Version differences such as iOS 15 vs iOS 17
• Android versions (API 28 to API 34)
• Manufacturer-specific layers (One UI, MIUI etc.)

Example:

• An application working on Android 13 crashes on Android 10

Tools such as SlumDroid can be used for this purpose.

This tests the compatibility of an application with desktop operating systems.

Commonly tested operating systems:

• Windows 7, 10, 11
• macOS Catalina, Big Sur, Monterey
• Linux distributions (Ubuntu, Fedora, CentOS)

Example:

• An enterprise software running on Windows 10 experiences font distortion after migration to Windows 11

Especially in industrial automation systems, this verifies whether software behaves identically in simulation environments (SiL) and on actual hardware (HiL).

Purpose:

• To test without exposing real hardware to risk
• To detect failure scenarios in advance

Compatibility testing is essential to ensure software products function correctly across numerous environments (different operating systems, browsers, hardware, networks, devices). However, implementing these tests is both costly and complex. The diversity of environments, number of devices, version differences, and frequent updates create various challenges in compatibility testing.

Below are these challenges categorized by topic:

One of the most fundamental challenges in compatibility testing is the sheer number of environments that must be tested.

Examples:

• The Android device market includes diverse manufacturers, processors, screen sizes, and interfaces.
• Web applications must be tested across dozens of different browsers and versions.
• Desktop applications must function on both 32-bit and 64-bit systems.

This diversity complicates defining test scope, prioritizing environments, and acquiring devices.

Operating systems, mobile platforms, and web browsers are continuously updated. These updates can sometimes cause existing software to behave incompatibly.

Issues:

• Application crashes after a new iOS update
• UI behavior breaks due to changes in Chrome’s JavaScript engine

Failure to synchronize compatibility testing with these updates can lead to serious user experience issues.

Compatibility testing is performed based on current platforms. However, testing on future devices, operating systems, or network architectures is impossible. For example: It is unknown whether software will work with an Android version to be released next year.

This weakens the “future-proofing” approach to software development.

Testing on real devices provides more accurate results than virtual devices. However, this method is expensive.

Cost components:

• Device purchase and update costs
• Test lab setup
• Hardware maintenance and security issues

Therefore, companies often use emulators/simulators; however, these cannot fully reflect all hardware behaviors and may produce misleading results. The recommended solution is to use web-based testing services (BrowserStack, Sauce Labs, etc.) for test automation.

Compatibility testing requires executing tests across various environment combinations, either manually or automatically. This process:

• Is time-consuming (repeated testing in each environment)
• Requires a large testing engineering team

For limited teams, compatibility testing is often delayed or inadequately performed, leading to post-release user complaints.

The most common errors found in compatibility testing are interface issues. These errors manifest differently across platforms.

Common UI errors:

• Font changes
• Button alignment issues
• Color, theme, or icon distortions
• Scroll bar problems
• Content overflow or overlapping

These errors are typically detected through manual testing; however, automation tools often lack the ability to accurately recognize UI elements.

Since browsers differ in their CSS, HTML, and JavaScript engines, a web application may not appear or function identically across all browsers.

Issues:

• An animation working in Chrome but not in Safari
• JavaScript errors in Internet Explorer
• Safari’s inability to properly display high-resolution media content

These issues can cause both functional and aesthetic disruptions.

In software integrated with other systems (e.g., REST APIs, external services), integration incompatibilities may occur.

Causes:

• Differences in JSON/XML formats
• Incompatible authentication protocols
• Synchronization errors in real-time data transmission

Such issues can lead to business interruptions and customer dissatisfaction, especially in enterprise software.

Since it is impossible to test all platforms, priority environments must be identified. However, errors in this phase:

• Lead to overlooking critical platforms
• Fail to simulate real user environments

Different results across environments make it difficult to distinguish between general issues (present everywhere) and environment-specific ones. This can misdirect error-fixing priorities.