How to create a Test Data Builder

Environment

• Maven
• Java JDK 21+
• Lombok plugin
• Enable Annotation Processing

Project Structure

The project structure is described in a logical way showing how is the easiest way to create an object with data to use in your test and, in the end, the recommendation using the Test Data Builder.

src/main

model/plain

The UserRegistration class is a plain object with getters and setters, constructor and toString().

The UserRegistrationBuilder is the Builder pattern applied using the UserRegistration class to make easier the object creation.

⚠️ This approach is not recommended but if you're not used to creating Java classes, this might be helpful.

model/lombok

To avoid you to write get, setters, toString, and builders you can use Lombok. On the UserRegistration class you can see the @Data and Builder that, respectively, automatically create the get and setters, and the builder.

⚠️ This approach is not recommended. The only difference between this and the plain approach is that now we are using less code.

data

This package contains the Test Data Builder classes. Both classes on this package use UserRegister object created with Lombok.

The UserRegistrationFixedData has all the methods to create different data but with fixed data, which means your tests will have the same data all the time.

The UserRegistrationData has all the methods to create different dynamic data. Faker is being used to generate the data. Even though you use the same method twice in your test, the data will be different.

src/test

plain

The class PlainClassTest shows how is the process to create a test with data to use in your test in the regular way.

The class PlainClassUsingBuilderTest shows how is the process to create a test with data using a builder.

lombok

The class UsingLombokBuilderTest shows the same approach of the previous one, but using lombok with the builder in order to have less code.

data

The class UsingFixedDataTest shows how is the process to create a test with the Test Data Builder having fixed data.

This class is being used on UsingDynamicDataTest to show how is the process to create a test with the Test Data Builder having dynamic data.

resources

Log4J2 properties files used to show the log information in the console. Note that Log4J2 is being using directly on test classes PlainClassTest, PlainClassUsingBuilderTest and UsingLombokBuilderTest but when we start using a concrete example of the Test Data Builder the log is being used on these tests.

I created this approach to add the responsibility of the data longing in the right place: the place they are being generated.

References

• https://martinfowler.com/bliki/ObjectMother.html
• https://reflectoring.io/objectmother-fluent-builder
• https://blog.codeleak.pl/2014/06/test-data-builders-and-object-mother.html