##junit-drools##

Tiny little library that helps you to unit test your Drools based business rules. Few simple annotations making Drools unit tests clean an easily maintainable.

Preface

Testing Drools rules can be annoying. Framework itself does not contain any helper classes or JUnit integrations that saves us from writing lots of boilerplate code in each test unit class.

Example of Drools unit test taken from Drools JBoss Rules 5.X Developer's Guide - this it NOT how we want to write unit tests:

public class ValidationTest {
  static StatelessKnowledgeSession session;
  
  @BeforeClass
  public static void setUpClass() throws Exception {
    KnowledgeBuilder builder = KnowledgeBuilderFactory.newKnowledgeBuilder();
    builder.add(ResourceFactory.newClassPathResource("validation.drl"), ResourceType.DRL);
    if (builder.hasErrors()) {
      throw new RuntimeException(builder.getErrors().toString());
    }
    
    KnowledgeBaseConfiguration configuration = KnowledgeBaseFactory.newKnowledgeBaseConfiguration();
    configuration.setOption(SequentialOption.YES);

    KnowledgeBase knowledgeBase = KnowledgeBaseFactory.newKnowledgeBase(configuration);
    knowledgeBase.addKnowledgePackages(builder.getKnowledgePackages());
    
    session = knowledgeBase.newStatelessKnowledgeSession();
  }
  
  ....
}

junit-drools's goal is to fix it and make testing Drools easy.

I am not very experienced with Drools so the library actually does what was needed in project I was working with. You are welcome to add your improvements by sending pull requests.

Installation

1. Clone git repository: git clone https://github.com/maciejwalkowiak/junit-drools.git
2. Build & install: mvn clean install
3. Add repository and dependency to your pom.xml:

    <repository>
        <id>maciejwalkowiak.pl</id>
        <url>https://github.com/maciejwalkowiak/maven-repo/raw/releases/</url>
    </repository>

    <dependency>
        <groupId>pl.maciejwalkowiak</groupId>
        <artifactId>junit-drools</artifactId>
        <version>1.0</version>
        <scope>test</scope>
    </dependency>

Usage

junit-drools provides DroolsJUnitRunner class that handles most boilerplate code you need to write to set up knowledge base and Drools session.

Lets consider following example:

@RunWith(DroolsJUnitRunner.class)
@DroolsFiles(value = "helloworld.drl", location = "/drl/")
public class AppTest {

    @DroolsSession
    StatefulSession session;

    @Test
    public void should_set_discount() {
        Purchase purchase = new Purchase(new Customer(17));

        session.insert(purchase);
        session.fireAllRules();

        assertTrue(purchase.getTicket().isDiscount());
    }

    @Test
    public void should_not_set_discount() {
        Purchase purchase = new Purchase(new Customer(22));

        session.insert(purchase);
        session.fireAllRules();

        assertFalse(purchase.getTicket().isDiscount());
    }
}

• @RunWith(DroolsJUnitRunner) - inits JUnit runner for testing drools rules
• @DroolsFiles - for specifying the content for the rules session
  • @DroolsFiles#value is a set of drl files. drl files have to be on class path
  • @DroolsFiles#dsl is an optional DSL used for building the drl files
  • @DroolsFiles#location is relative to src/test/resources or src/main/resources
• @DroolsSession - autoinjects Drools session to your test before execution

Find full example with drl file in src/test directory of the project

In case you don't want to use DroolsJUnitRunner, for example because you already want to use Mockito or Spring runner you can initialize Drools objects in @Before method:

@DroolsFiles(value = "helloworld.drl", location = "/drl/")
public class BeforeMethodBasedTest {
    @DroolsSession
    StatefulSession session;

    @Before
    public void initDrools() throws Exception {
        new DroolsInjector().initDrools(this);
    }

    @Test
    public void should_set_discount() {
        Purchase purchase = new Purchase(new Customer(17));

        session.insert(purchase);
        session.fireAllRules();

        assertTrue(purchase.getTicket().isDiscount());
    }
}