Most unit tests for a Processor or a Controller Service start by creating an instance of the TestRunner class. In order to add the necessary classes to your Processor, you can use the Maven dependency:

<dependency>
 <groupId>org.apache.nifi</groupId>
 <artifactId>nifi-mock</artifactId>
 <version>${nifi version}</version>
</dependency>

We create a new TestRunner by calling the static newTestRunner method of the TestRunners class (located in the org.apache.nifi.util package). This method takes a single argument. That argument can either be the class of the Processor to test or can be an instance of a Processor.