Product flavor for using mock exposure notification API

In the code you mention a plan to add a product flavor that should use a mock exposure notification API: https://github.com/corona-warn-app/cwa-app-android/blob/a326bb4bfc2661b3e5ff8e53a1951b5ad351a395/Corona-Warn-App/build.gradle#L67-L77

Is this something that could be done as a contribution? Looking at InternalExposureNotificationClient it seems like one option could be to inject a different/mock ExposureNotificationClient implementation that returns some dummy values. This at least would allow launching the app without any API support on the device. Did you have more elaborate plans? (e.g. controlling the mocked API via an activity or test app?).

Would be interested in contributing this if possible.

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Internal Tracking ID: EXPOSUREAPP-1967

[pocmo]

Added a first iteration to my repository: https://github.com/pocmo/cwa-app-android/commit/7043609ea79b8ee062c2e1e6542d4c7391350424

In that patch I changed InternalExposureNotificationClient to delegate the creation of ExposureNotificationClient to a factory object. There are different versions of the factory for the device and deviceForTesters flavors. The device flavor continues to use Nearby.getExposureNotificationClient while the deviceForTesters returns a mock implementation that for now just returns hardcoded values for the API calls.

In further iterations I would like to (only in the deviceForTesters flavor):

• Introduce a test fragment (like you already have for testing the API and the risk level) that allows configuring what the API should return (e.g. values in ExposureSummary)
• Persist the values (e.g. SharedPreferences) to make them stable across app restarts and for background tasks.
• Provide a toggle in the test fragment to switch between using the actual API and the mock API.

[pocmo]

Alright, I’ll work in my fork for now and will report back once something interesting comes out of it.