Feature request: "Dry run" / Testability

[alixwar]

I feel that MixpanelAPI is lacking in terms of testability.

Situation right now (5.5.1)

• MixpanelAPI is not final which is good (= Possible to mock without bytecode manipulation)
• MixpanelAPI does not have a public constructor (= Not possible to create dummy subclasses)
• MixpanelAPI.getInstance() returns null under Robolectric ( = Tests fail due to NPE)

Workaround

• Setting up a wrapper class for MixpanelAPI where the tests replace the "real" instance (=null) with a mock instance

Suggestions (alternatives)

• (my favourite suggestion) Make constructor public so that integrators can create their own dummy implementations of MixpanelAPI and e.g. use the Shadow feature of Robolectric
• (perhaps too much....) Release a mocking-library, mixpanel-android-mock with an API that configures Mixpanel ("dry run") to return reasonable dummy objects. Example of such library: https://github.com/square/retrofit/tree/master/retrofit-mock

[patedit]

Thanks a lot for the suggestion! So I understand it a bit better, can you pass a mock context when creating a Mixpanel instance?

[alwa]

@patedit Yes, Robolectric can create such fake contexts

[alixwar]

@patedit Any updates on this?

[alixwar]

My workaround:

New class:

package com.mixpanel.android.mpmetrics;

// Imports...
public class StubbedMixpanelAPI extends MixpanelAPI {

    @SuppressLint("NewApi")
    public StubbedMixpanelAPI(@NonNull Context context) {
        super(context, CompletableFuture.completedFuture(
                context.getSharedPreferences("dummy", Context.MODE_PRIVATE)), "", true);
    }

}

When I instantiate MixpanelAPI:

...

isRoboUnitTest() ? new StubbedMixpanelAPI(context) : MixpanelAPI.getInstance(context, BuildConfig.ANALYTICS_TOKEN, false);

...

private static boolean isRoboUnitTest() {
   return "robolectric".equals(Build.FINGERPRINT);
}

[patedit]

Thanks for the snippet @alixwar. Sadly adding this feature is not on our roadmap and since there is an existing workaround, other devs will find this useful.

[alixwar]

With the new "Looper mode" in Robolectric, the workaround is now broken unfortunately