Mockito verification for RxJava subscriptions

Mockito offers a powerful set of tools for JVM developers to create mock dependencies and verify particular method calls on them.

However, when your mocks return async RxJava types (e.g. Observable, Single, Completable) you often want to go a step further and verify that the reactive objects returned from your mocks were actually subscribed to.

This is a small extension to Mockito that allows you to do this.

More generally, this extension aims to allow you to verify asynchronous "invocations" on mocks in addition to regular synchronous ones, with minimal boilerplate code and impact on readability.

Basic Usage

Given a dependency you'd like to mock:

interface Repository {
    fun getItems(): Observable<String>
}

Create your mock passing a ReturnsTrackedRx1Types() or ReturnsTrackedRx2Types() as its default Answer:

val mockRepository = Mockito.mock(Repository::class.java, ReturnsTrackedRx1Types())

You can now verify subscriptions with wasSubscribedTo():

verify(mockRepository, wasSubscribedTo()).getItems()

I.e. this will cause your test to fail if the Observable returned by getItems() has not been subscribed to by the time it's run.

More Usage Examples

Verify that the mock's return value was never subscribed to with:

verify(mockRepository, neverSubscribedTo()).getItems()

Argument matchers work as expected:

verify(mockRepository, wasSubscribedTo()).getItems(limit = eq(10))

Calling reset on a mock will reset recorded subscriptions, just like regular invocations:

mockRepository.getItems().subscribe({}, {})

reset(mockRepository)

verify(mockRepository, wasSubscribedTo()).getItems()    // will fail!

For more usage examples, check out the Unit Tests.

RxJava 1 Support

wasSubscribedTo() will detect subscriptions on RxJava1 base types (Observable, Completable and Single) on mocks created with ReturnsTrackedRx1Types().

RxJava 2 Support

wasSubscribedTo() will detect subscriptions on RxJava2 base types (Flowable, Observable, Completable, Single and Maybe) on mocks created with ReturnsTrackedRx2Types().

Limitations (TODO)

This is currently missing support for:

• In-order verifications
• No informative error when attempting to use the verification without creating the mock correctly
• Subscriptions can't be currently be tracked if you provide your own stubs for observable-returning methods

Download

Step 1.

Add the JitPack repository to your root build.gradle at the end of repositories:

allprojects {
    repositories {
        // ...
        maven { url 'https://jitpack.io' }
    }
}

Step 2.

Add the dependency to your app's build.gradle

RxJava1:

dependencies {
    compile 'com.github.kiwiandroiddev.mockito-verify-subscriptions:rxjava1:v0.2-alpha'
}

RxJava2:

dependencies {
    compile 'com.github.kiwiandroiddev.mockito-verify-subscriptions:rxjava2:v0.2-alpha'
}