Use test data in Java with DataFaker

DataFaker is a library for Java that allows you to easily generate test data. This can be useful in situations where data is needed to generate tests, a demonstration or simply to fill a database with test data, and avoid having to do it manually. This library is based on Java Faker (although it has not been updated for some time) and has more than 200 different data providers, so the type of data that can be generated is very varied.

Facility

DataFaker can be installed using Maven, Gradle or Ivy, in this case Maven will be used, so you only need to add the following dependency to the pom.xml file:

<dependency>
    <groupId>net.datafaker</groupId>
    <artifactId>datafaker</artifactId>
    <version>2.4.0</version>
</dependency>

Use

To use DataFaker, you must create an instance of the DataFaker class and then you can use the methods of this class to generate the test data.

Faker f = new Faker();

For example, if you need a first and last name you can use one of the methods within name():

var name = f.name().firstName();
var lastName = f.name().lastName();
System.out.println("Hello, my name is " + name + " " + lastName);

// Output
Hello, my name is Patsy Heller

If we run the above code a couple of times, we can see that the generated names are different and are in a different language. To make the data even more realistic you can specify a Locale parameter within the Faker constructor in one of the following ways:

Faker f = new Faker(Locale.ENGLISH);

Faker f = new Faker(Locale.forLanguageTag("es"));

Faker f = new Faker(Locale.forLanguageTag("es-MX"));

Faker f = new Faker(new Locale("es")); // Esto esta deprecado desde el JDK 19

Using any of the previous options, the data generated will be in the specified language, although it depends on each data provider whether it supports it or not. For more information about the Premises you can consult the official documentation.

To make a more varied example, consider the following record of type Person:

public record Person(Integer id, String firstName, String lastName, String username, String address, String job, String favoriteColor) { }

A list of 10 people with test data can now be generated as follows:

Faker f = new Faker(Locale.forLanguageTag("es-MX"));
List<Person> persons = new ArrayList<>();

for (int i = 0; i < 10; i++) {
    persons.add(
            new Person(
                    f.number().numberBetween(1, 1000),
                    f.name().firstName(),
                    f.name().lastName(),
                    f.internet().username(),
                    f.address().fullAddress(),
                    f.job().title(),
                    f.color().name()
            )
    );
}

Finally, the list of generated people can be printed:

persons.forEach(System.out::println);

In this way test data can be generated easily and quickly using DataFaker, for more information about the available data providers you can consult the official documentation.

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