How to test validation annotations of a class using JUnit?

I need to test the validation annotations but it looks like they do not work. I am not sure if the JUnit is also correct. Currently, the test will be passed but as you can see the specified email address is wrong.

JUnit

public static void testContactSuccess() {
        Contact contact = new Contact();
        contact.setEmail("Jackyahoo.com");
        contact.setName("Jack");
        System.err.println(contact);
    }

Class to be tested

public class Contact {

    @NotNull
    @Size(min = 1, max = 10)
    String name;

    @NotNull
    @Pattern(regexp="[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\\."
            +"[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@"
            +"(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?",
                 message="{invalid.email}")
    String email;

    @Digits(fraction = 0, integer = 10)
    @Size(min = 10, max = 10)
    String phone;

    getters and setters

}

Solution 1:

The other answer saying that "the annotations do not do anything by themselves, you need to use a Validator to process the object" is correct, however, the answer lacks working instructions on how to do it using a Validator instance, which for me was what I really wanted.

Hibernate-validator is the reference implementation of such a validator. You can use it quite cleanly like this:

import static org.junit.Assert.assertFalse;

import java.util.Set;

import javax.validation.ConstraintViolation;
import javax.validation.Validation;
import javax.validation.Validator;
import javax.validation.ValidatorFactory;

import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;

public class ContactValidationTest {

    private Validator validator;

    @Before
    public void setUp() {
        ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
        validator = factory.getValidator();
    }
    @Test
    public void testContactSuccess() {
        // I'd name the test to something like 
        // invalidEmailShouldFailValidation()

        Contact contact = new Contact();
        contact.setEmail("Jackyahoo.com");
        contact.setName("Jack");
        Set<ConstraintViolation<Contact>> violations = validator.validate(contact);
        assertFalse(violations.isEmpty());
    }
}

This assumes you have validator implementation and junit as dependencies.

Example of dependencies using Maven pom:

<dependency>
    <groupId>org.hibernate</groupId>
    <version>5.2.4.Final</version>
    <artifactId>hibernate-validator</artifactId>
</dependency>
<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.12</version>
    <scope>test</scope>
</dependency>

Solution 2:

A simple way to test validation annotations using javax:

Declare the Validator at Class level:

private final Validator validator = Validation.buildDefaultValidatorFactory().getValidator();

Then in your test simply call it on the object you require validation on, with what exception you are validating:

Set<TheViolation<TheClassYouAreValidating> violations = validator.validate(theInstanceOfTheClassYouAreValidating);

Then simply assert the number of expected violations:

assertThat(violations.size()).isEqualTo(1);

You will need to add this to your dependencies (gradle):

compile group: 'javax.validation', name: 'validation-api', version: '2.0.1.Final'