mockito-threadsafe-mockmaker - threadsafe mocks with Mockito

What it does

Executes the mock invocation under a synchronized(mockobject) { …​ } block. This makes it possible to use Mockito mocks in a multi-threaded test. Mockito is not thread-safe itself. One sign of problems are NullPointerExceptions without proper explanation. For example, a mocked method return value might be null from time to time and this leads to flaky tests. Multi-threaded tests are more common with the rise of popularity of reactive programming where a simple integration test scenario might be executed on multiple threads.

Usage

Adding the dependency will activate the Mockito MockMaker extension provided by this library.

This library is available via Jitpack. The repository information is at https://jitpack.io/#lhotari/mockito-threadsafe-mockmaker .

Adding dependency in Gradle

repositories {
    maven {
        url 'https://jitpack.io'
        content {
            // limits using the jitpack repository for specific artifacts
            includeGroup 'com.github.lhotari'
        }
    }
}

dependencies {
    testImplementation 'com.github.lhotari:mockito-threadsafe-mockmaker:0.1.0'
}

Adding dependency in Maven

<repositories>
    <repository>
        <id>jitpack.io</id>
        <url>https://jitpack.io</url>
    </repository>
</repositories>

<dependency>
    <groupId>com.github.lhotari</groupId>
    <artifactId>mockito-threadsafe-mockmaker</artifactId>
    <version>0.1.0</version>
    <scope>test</scope>
</dependency>

Usage in code

synchronize access on the mock object’s object monitor when stubbing the methods. synchronization is also required for verification.

SomeClass mymock = mock(SomeClass.class);
synchronized (mymock) {
    when(mymock.someMethod()).thenReturn(new Something());
    ....
}

...
// code that uses the mock in some other thread
...

synchronized (mymock) {
   verify(mymock, times(1)).someMethod();
}