Custom sharding JSON

[asadsalman]

I want to be able to provide a custom android_shards.json to Flank, so I can write custom sharding logic for my tests.

Solution
Flank produces an android_shards.json file after parsing APK etc. I want to be able to provide a custom one myself. Flank will construct and execute whatever shards are declared in the custom android_shards.json.

Alternatives
Flank (and gcloud) do provide test-targets-for-shard flag. That will achieve what I'm looking for but, in its current form, it would be pretty hard to use since I would have to write a flank.yml file for each shard.

[jan-goral]

Looks like a really nice feature.

TODO:

1. New config option
2. android_shards.json to InstrumentationTestContext mapper
3. Update List<AndroidTestContext>.setupShards function for using shards from android_shards.json if option is specified.
   • Validate data loaded from android_shards.json in AndroidArgs context
   • Print proper log if some error occurs.
4. Test the happy path and each known exception.

Just leaving a quick note for estimation.

[bootstraponline]

I think we should also support custom sharding JSON on iOS.