How to initialize an instance of the constraint annotation while writing unit tests for a javax.validation.ConstraintValidator

ExampleConstraint.java

import javax.validation.Constraint;
import javax.validation.Payload;
import java.lang.annotation.*;

@Documented
@Constraint(validatedBy = ExampleConstraintValidator.class)
@Target({ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
public @interface ExampleConstraint {

    String message() default "{error.example_constraint.invalid}";

    String customField() default "...";

    Class<?>[] groups() default {};

    Class<? extends Payload>[] payload() default {};

}

ExampleConstraintValidator.java

import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;

public class ExampleConstraintValidator implements ConstraintValidator<ExampleConstraint, String> {

    private String customField;

    @Override
    public void initialize(ExampleConstraint constraintAnnotation) {
        this.customField = constraintAnnotation.customField();
    }

    @Override
    public boolean isValid(String value, ConstraintValidatorContext context) {
        // Your business logic
    }

}

ExampleConstraintValidatorTests.java

import org.hibernate.validator.internal.util.annotation.AnnotationDescriptor;
import org.junit.jupiter.api.Test;

import java.util.Collections;

import static org.assertj.core.api.Assertions.assertThat;

class ExampleConstraintValidatorTests {

    @Test
    void should...() {
        final ExampleConstraintValidator exampleConstraintValidator = new ExampleConstraintValidator();

        final ExampleConstraint exampleConstraint = new AnnotationDescriptor.Builder<>(ExampleConstraint.class, Collections.singletonMap("customField", "...")).build().getAnnotation();

        exampleConstraintValidator.initialize(exampleConstraint);

        assertThat(exampleConstraintValidator.isValid("...", null)).isTrue();
    }

}