Testing
Unit Testing
Skip always transpiles your XCTest unit tests into JUnit tests for Android. This means that you can only perform Android tests on compiled Swift that has been bridged to Kotlin/Java. Unit tests involving unbridged types should be excluded from Android testing.
final class MyNativeSwiftTests: XCTestCase {
...
#if !os(Android)
func testSomeUnbridgedSwift() {
...
}
#endif
...
}
We will offer Android unit testing of unbridged native code in a future release. If you are using Skip Lite, all of your code is transpiled, so you do not have to limit your testing to bridged types.
Robolectric Testing
The SkipUnit module documentation describes the ability to unit test your code in an Android environment running on your Mac, which can be faster than using the Android emulator. If you choose to test on your Mac, Skip uses a simulated Android environment called Robolectric.
#if os(Android) checks will evaluate to false under Robolectric, even though you should generally be exercising the Android code path. So Skip also defines the ROBOLECTRIC symbol in your Robolectric testing builds. If you want to be sure that your compiled Swift takes the Android code path whether running on device, emulator, or in Robolectric, use #if os(Android) || ROBOLECTRIC.
Android Emulator/Device Testing
To run your test cases on an Android device or emulator, you can specify the ANDROID_SERIAL environment variable in the Xcode scheme’s Run action arguments for the target. The default emulator is usually “emulator-5554”, and to see the list of identifiers for any connected devices, run the command adb devices.
Running tests against an emulator or device is slower than running against Robolectric, but the results will be much more representative of how the code will behave in the real world. This is true for both purely transpiled projects, as well as a natively-compiled SkipFuse project.
For an example of a repository that utilizes SkipFuse bridge testing, along with GitHub CI actions that automatically perform the testing against an Android emulator, see https://github.com/skiptools/skip-fuse-samples.
Non-Skip Packages
Testing of native Swift packages that compile for both iOS and Android and do not have a skip.yml - such as the thousands of third-party packages tracked by swiftpackageindex.com’s Android compatibility testing - is discussed in the Porting Guide.
Performance Testing
There is often a significant difference between Debug and Release build performance on Android devices. Always run on a device using a Release build when testing real-world performance.