In the world of mobile app testing, it’s common to hear people talk about simulators and emulators as if the terms are synonymous.
To a certain extent, that makes sense. Simulators and emulators are similar in many ways, and the differences between them don’t always matter from the perspective of a test engineer.
But the fact remains that simulators and emulators are different beasts. If you want to make the most of each type of software testing tool, it’s important to understand what makes simulators different from emulators, and why you’d choose to use one or the other.
Simulators and Emulators: What They Have in Common
To begin, let me explain how simulators and emulators are similar to each other.
Emulators and simulators both make it possible to run software tests inside flexible, software-defined environments. In this way, they allow you to run tests more quickly and easily than you could if you had to set up a real hardware device. Both are essential for improving development efficiency and expanding testing coverage, particularly in cross-platform or multi-device scenarios.
That is why simulators and emulators are typically used to perform most software tests. Real-device testing tends to be performed only late in the software delivery pipeline, just before releasing software into production. That way, you can take advantage of the
speed and flexibility of simulated and emulated test environments for most software tests, while still getting a deep insight into real-device testing before you release your software to end users.
Simulators vs. Emulators: How They’re Different
A simulator is designed to create an environment containing all of the software variables and configurations that will exist in an app’s production environment- in contrast, an emulator attempts to mimic all of the hardware features of a production environment and software features.
For emulators, you typically need to write an emulator using assembly language to achieve this. However, simulators do not attempt to emulate the actual hardware that will host the application in production. Because simulators create only software environments, they can be implemented using high-level programming languages. In a sense, then, you can think of emulators as occupying a middle ground between simulators and real devices. Whereas simulators only mimic environment features that can be configured or defined using software, emulators mimic both hardware and software features.
Of course, because emulators may not do a perfect job of emulating the hardware and software of a production environment, they are not a substitute for real-device testing. They just allow you to set up an environment that is closer to the one you’d have on a real device.
When to Use Simulators
Typically, simulators are best for software testing scenarios in which you’re focused on making sure that an application performs as expected when interacting with external applications or environments.
For example, you may want to test an app’s ability to send data to another application. A simulated environment will typically suffice for this because the underlying hardware configuration is unlikely to have much of an impact on data transactions for your application. Similarly, if you want to make sure that an application’s interface displays properly under different screen resolutions, simulated testing environments are appropriate.
While iOS simulators are commonly used for testing iPhone and iPad apps on macOS, other platforms also have simulators. For example, Android simulators can simulate device behavior in a software environment, though Android emulators are more commonly used for replicating full device hardware and software. Simulators typically focus on the software layer, regardless of the platform.
When to Use Emulators
On the other hand, emulators are most useful when you need to test how software interacts with underlying hardware or a combination of hardware and software.
Do you want to know whether a firmware update will cause problems for your application? An emulator can help you find that out. Or perhaps you need to know how your application performs using different types of CPUs or different memory allocations. These are also scenarios where emulators come in handy.
Feature | Emulators | Simulators |
Device Representation | Recreates the complete hardware configuration (processor, memory, sensors, etc.). | Focuses on software aspects, without hardware-level precision. |
Testing Capabilities | Ideal for testing hardware-dependent features (e.g., sensors, graphics, device-specific behaviors). | Best for testing the functionality of the app, UI/UX behavior, and performance under normal conditions. |
Use Case | Suitable for testing apps with complex device interactions or specific hardware needs. | More suited for testing the app's behavior in a specific OS or interface scenario. |
Performance Testing | Can simulate real-world performance but may not be as fast as actual devices due to resource demands. | Does not simulate real-world device performance, often used for quick functional testing. |
Start Mobile Testing With Simulators, Emulators, and Real Devices
To ensure thorough app testing, it's crucial to combine emulators, simulators, and real devices. Emulators and simulators are ideal for early-stage testing of functionality and user experience, while real devices provide the most accurate insights into performance and hardware interactions. By using all three in your testing workflow, you can ensure your app delivers the best possible experience across a range of platforms. With Sauce Labs, you can seamlessly integrate emulators, simulators, and real devices into your testing process, helping you create reliable, high-performing apps.
