migrated assertion to assertJ

src/test/java/org/springframework/samples/petclinic/model/ValidatorTests.java

@@ -8,8 +8,6 @@ import java.util.Set;
 import javax.validation.ConstraintViolation;
 import javax.validation.Validator;
 
-import org.assertj.core.api.Assertions;
-import org.junit.Assert;
 import org.junit.Test;
 import org.springframework.context.i18n.LocaleContextHolder;
 import org.springframework.validation.beanvalidation.LocalValidatorFactoryBean;
@@ -40,7 +38,7 @@ public class ValidatorTests {
         Validator validator = createValidator();
         Set<ConstraintViolation<Person>> constraintViolations = validator.validate(person);
 
-        Assert.assertEquals(1, constraintViolations.size());
+        assertThat(constraintViolations.size()).isEqualTo(1);
         ConstraintViolation<Person> violation =  constraintViolations.iterator().next();
         assertThat(violation.getPropertyPath().toString()).isEqualTo("firstName");
         assertThat(violation.getMessage()).isEqualTo("may not be empty");