Creating objects

Fixture Monkey works in both Java and Kotlin. We have a separate 'Getting Started' page for each environment you can use: Java, Java without Lombok, and Kotlin.

This page explains the Java environment. Please refer to the appropriate page for your environment.

Creating test objects with Fixture Monkey is remarkably simple. Here's how you can use it:

@Test
void test() {
    // given
    FixtureMonkey fixtureMonkey = FixtureMonkey.builder()
        .objectIntrospector(ConstructorPropertiesArbitraryIntrospector.INSTANCE)
        .build();

    // when
    Product actual = fixtureMonkey.giveMeOne(Product.class);

    // then
    then(actual).isNotNull();
}

When you run this code, Fixture Monkey will generate a Product instance with random values. Below is just an example, and the actual values will be different each time:

Product(
    id=42,
    productName="product-value-1",
    price=1000,
    options=["option1", "option2"],
    createdAt=2024-03-21T10:15:30Z,
    productType=ELECTRONICS,
    merchantInfo={1="merchant1", 2="merchant2"}
)

Understanding the Setup

First, create a FixtureMonkey instance that facilitates the creation of test fixtures. The key part is choosing the right Introspector — it defines how Fixture Monkey creates objects.

Choosing an Introspector

The introspector you need depends on how your class is structured:

Your class has...	Use this introspector
Lombok @Value / @AllArgsConstructor	ConstructorPropertiesArbitraryIntrospector
No-args constructor + setters	BeanArbitraryIntrospector (default)
Jackson annotations	JacksonObjectArbitraryIntrospector (via Jackson Plugin)
Kotlin data class	PrimaryConstructorArbitraryIntrospector (via Kotlin Plugin)

For more details, see the Introspectors section.

Example Class

For this example, we use a Lombok @Value class:

tip

Add lombok.anyConstructor.addConstructorProperties=true to your lombok.config file. This is required for ConstructorPropertiesArbitraryIntrospector to work with Lombok.

@Value
public class Product {
    long id;
    String productName;
    long price;
    List<String> options;
    Instant createdAt;
    ProductType productType;
    Map<Integer, String> merchantInfo;
}

(If you're working without Lombok, see creating objects without Lombok)

Next Steps

Now that you can create objects, learn how to customize them to match your test scenarios.