This Android / Gradle project on GitHub shows how to integrate Couchbase, Robolectric and Dagger so that unit testing can occur without the need for a connected device or emulator.
I need a database for my TripComputer app so that users can keep a log of their Journeys. I could use SQL Lite, but I prefer not to use SQL if possible. With SQL you’re forced to maintain a fixed schema and SQL Lite doesn’t offer any out of the box cloud replication capabilities, unlike most NoSQL databases.
Couchbase Lite for Android is an exciting new embedded NoSQL database, but because its ‘Database’ and ‘Manager’ classes are Final and require native code, it’s not trivial to mock them or integrate them into apps that utilise the popular Robolectric testing framework.
Therefore, in order to support off-device Java VM based testing with Robolectric it is necessary to write custom interfaces and use a dependency injection framework that will allow the injection of mock objects to occur when testing. To achieve this ‘dependency injection’ of mocks, I’ve used Mockito and introduced the Dagger framework into the code.
- Couchbase-lite 184.108.40.206
- Robolectric 2.4
- Dagger 1.2.2
- Mockito 1.10.19
- Android Studio 1.1 Beta 3 (optional)
About The Sample App
The App I’ve built here is very simple. When the user clicks the Save button on the screen, in the background a new document (technically a `java.util.Map`) is created and saved to the embedded Couchbase NoSQL database. While saving the new document, Couchbase automatically assigns it an ID and it is this ID that is ultimately displayed to the user on the screen after they’ve clicked the Save button. The document id’s in Couchbase take the form of GUID’s.
The App Code
Roughly speaking, in the `app` codebase you’ll see the following…
1. `MyActivity.java` is a simple Android action bar activity that extends a `BaseActivity` and requires a `PersistanceManager` to be injected at runtime so it can talk to the database.
2. `PersisitanceManager.java` is a class that acts as a DAO object to `MyActivity`, managing the persistence of ‘Map’ objects. It offers only INSERT and GET operations in this sample and requires a `PersistanceAdapter` implementation to be injected into it.
3. `PersistanceAdapter.java` is an interface that defines INSERT and GET operations on `Map` objects. This interface is required later when mocking & testing.
4. `CouchbasePersistanceAdapter.java` is a concrete implementation of the `PersistanceAdapter` interface. It utilises Couchbase and depends on a couchbase `Database` object which must be constructed by Dagger and injected into it.
5. The injectable objects that require non-trivial instantiation (like the Couchbase `Database` object for example) are defined by `@Provides` methods in a Dagger `@Module` in the `MyActivityModule` class.
At runtime, Dagger, `MyActivity`, `BaseActivity` and the `App` application classes take care of constructing an `ObjectGraph` for the application and inserting the required dependencies so that all the various `@Inject` requirements can be met. The “Instrumentation (integration) Tests” in the Android App gradle project test that this integration and dependency injection is working as expected.
The Robolectric Tests
Because it’s also desirable to perform testing without a device or emulator, there’s a set of Robolectric tests for the App’s `MyActivity` class that test the same ‘Save’ feature but without the need for a connected or emulated device and without the need for an embedded Couchbase database.
In the `app-test` gradle project you’ll see the following…
1. `MyTestActivity.java` extends the MyActivity class and `@Overrides` the `getModules()` method. This method constructs and returns a `TestMyActivityModule` instance. `TestMyActivityModule` is an inner class which defines an alternative (overriding) Dagger `@Module` that can also provide a `PersistanceManager` for injection into the `MyTestActivity` when testing. This module `@Provides` a fake, programmable `PersistenceManager` _mock_, not a real persistance manager as is expected under normal conditions.
2. `MyActivityRobolectricTest.java` is a standard Robolectric test, but it’s Robolectric controller builds a new `MyTestActivity`. The method `testClickingSaveButtonSavesMapAndDisplaysId()` tests that clicking the _Save_ button has the required affect by pre-programming the `PersistenceManager` mock with behaviours and then verifying that this mock has indeed been called by the Activity as expected.
Running the Sample
To run the tests for yourself just clone or download this repository and then execute the following gradle commands. For completeness, I’ve included some Android Instrumentation Tests as well and you can run them with `gradlew connectedCheck` (assuming an emulator or device is present).
gradlew connectedCheck (this is optional and assumes a device is present)
Many thanks to Andy Dennie for his Dagger examples on GitHub. These were really helpful to this Dagger noob when trying to understand how to integrate Dagger with Android.
About the Author
Ben Wilcock is the developer of TripComputer, the only distance tracking app for Android with a battery-saving LOW POWER mode. It’s perfect for cyclists, runners, walkers, hand-gliders, pilots and drivers. It’s free! Download it from the Google Play Store now:- Get the App on Google Play