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Metronome: A Fully Unit-Tested Rx-Based Reference Application

Cain Wong
Cain Wong
Jan 14, 2016 · 3 min read

Several months ago, as a way to get myself up to speed with using and unit-testing RxJava, I developed and posted this reference application. I had ambitions of immediately following it up with a blog post, but I got distracted and I never got around to sharing it with anyone. So better late than never I suppose.

Use Case

The application is that of a metronome with the following features:

  • A core metronome “engine” which triggers “beat” events on a timed interval. The engine exposes methods for starting and stopping the metronome, as well as a method for changing the tempo (i.e. the time between beats).

Implementation and Testing Details

I won’t cover every aspect of how I implemented the features of the application, but I think it is worth highlighting a few details:

  • I used Hugo Visser’s android-apt plugin because I found that the built-in Gradle “provided” functionality didn’t reliably do the apt code-generation for Dagger 2. Dagger 1 worked fine for me without this plug-in, but now that I have transitioned to Dagger 2, android-apt is a must.


The source code of the project is available here:

Also, here is a list of the tools/libraries that I used:

I hope that this post and the sample application are helpful. Feel free to ask me any questions or offer any suggestions. Cheers!

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