Setting up Tests

Reactor provides a dedicated set of classes for testing reactive sequences that are grouped in the artifact reactor-test.

This means that to use those classes, in addition to reactor-core, you must add reactor-test as a test dependency of your project.

In Maven, add the following to the dependencies section of your pom.xml file:

<dependency>
    <groupId>io.projectreactor</groupId>
    <artifactId>reactor-test</artifactId>
    <scope>test</scope>
</dependency>

Remember that if you use reactor-bom, you don’t need to specify a version.

If you use Gradle, add the following dependency to the build.gradle file:

dependencies {
   testCompile 'io.projectreactor:reactor-test'
}

After adding this dependency, the external libraries section of your project should look something like this:

If you open the reactor-test JAR file, you’ll see the following classes and interfaces:

The main interface of reactor-test is StepVerifier, which provides a step by step, declarative way of testing how a reactive sequence behaves upon subscription.

But there are others less-known classes or interfaces, that can be useful. For example, PublisherProbe and TestPublisher, which are both in the publisher package:

Let’s start with StepVerifier and its API.