Extract settings import

[XiangRongLin]

What is it?

• Codebase improvement (dev facing)

Description of the changes in your PR

• Extract logic for settings import out of ContentSettingsFragment into ContentSettingsManager and ZipHelper
• Add basic unit tests for ContentSettingsManager
• Introduce NewPipeFileLocator which resolves the db and settings files. Inject it into ContentSettingsManager
• remove subclass ExportTest. No benefit with only one test
• added real zip file and newpipe.settings of export as test resources

APK testing

app-debug.zip

https://github.com/TeamNewPipe/NewPipe/actions/runs/459642451

Due diligence

• I read the contribution guidelines.

Notes

• The git history went wide, because while extracting it I found my initial approach for DI and testing not good. Easiest would be to just squash everything together.
• With this changes to the import/export logic should always be covered by additional unit tests

[Stypox]

Looks good to me. Thank you!

[Stypox]

@XiangRongLin I am unable to run ContentSettingsManagerTest on my machine. I am unable to debug #5415 tests.

Cannot mock/spy class org.schabi.newpipe.settings.NewPipeFileLocator
Mockito cannot mock/spy because :
 - final class

If I make NewPipeFileLocator an open class (in kotlin classes are final by default), I get null pointer exceptions whenever something is being mocked, like 'when'(fileLocator.db).thenReturn(db).

[XiangRongLin]

@Stypox Did you sync the Gradle files? Because the mockito-inline dependency should fix the problem with mocking final classes/methods

[XiangRongLin]

@Stypox the NullPointerExceptionoccurs for the same reason. Methods are final by default, so mockito can't mock then out of the box.