Stub value of Build.VERSION.SDK_INT in Local Unit Test

As an alternative to reflection, you can use your own class that checks for API and then use Mockito to test the API-Dependent logic in fast JVM unit tests.

Example class

import android.os.Build

class SdkChecker {

    fun deviceIsOreoOrAbove(): Boolean = Build.VERSION.SDK_INT >= Build.VERSION_CODES.O

}

---

Example tested method

fun createNotificationChannel(notificationManager: NotificationManager) {
    if (sdkChecker.deviceIsOreoOrAbove()) { // This sdkChecker will be mocked
        // If you target Android 8.0 (API level 26) you need a channel
        notificationManager.createNotificationChannel()
    }
}

---

Example unit tests

import com.nhaarman.mockito_kotlin.mock
import com.nhaarman.mockito_kotlin.verify
import com.nhaarman.mockito_kotlin.verifyZeroInteractions
import com.nhaarman.mockito_kotlin.whenever

@Test
fun createNotificationChannelOnOreoOrAbove() {
    whenever(mockSdkChecker.deviceIsOreoOrAbove()).thenReturn(true)

    testedClass.createNotificationChannel(mockNotificationManager)

    verify(mockNotificationManager).createNotificationChannel()
}

@Test
fun createNotificationChannelBelowOreo() {
    whenever(mockSdkChecker.deviceIsOreoOrAbove()).thenReturn(false)

    testedClass.createNotificationChannel(mockNotificationManager)

    verifyZeroInteractions(mockNotificationManager)
}

Change the value using reflection.

 static void setFinalStatic(Field field, Object newValue) throws Exception {
    field.setAccessible(true);

    Field modifiersField = Field.class.getDeclaredField("modifiers");
    modifiersField.setAccessible(true);
    modifiersField.setInt(field, field.getModifiers() & ~Modifier.FINAL);

    field.set(null, newValue);
 }

And then

 setFinalStatic(Build.VERSION.class.getField("SDK_INT"), 123);

It is tested. Works.

Update: There is a cleaner way to do it.

Create an interface

interface BuildVersionProvider {

    fun currentVersion(): Int

}

Implement the interface

class BuildVersionProviderImpl : BuildVersionProvider {

    override fun currentVersion() = Build.VERSION.SDK_INT

}

Inject this class as a constructor argument through the interface whenever you want current build version. Then in the tests when creating a SUT (System Under Test) object. You can implement the interface yourself. This way of doing things may be more code but follows the SOLID principles and gives you testable code without messing with reflection and system variables.