Spring MVC Integration Testing: Assert the given model attribute(s) have global errors

In order to report a global error in Spring MVC using Bean Validation we can create a custom class level constraint annotation. Global errors are not associated with any specific fields in the validated bean. In this article I will show how to write a test with Spring Test that verifies if the given model attribute has global validation errors.

30/03/2016 - The project referenced in this article got a solid upgrade, as well as the related blog post: Different ways of validating @RequestBody in Spring MVC with @Valid annotation.

Custom (Class Level) Constraint

For the sake of this article, I created a relatively simple class level constraint called SamePassword, validated by SamePasswordValidator:

@Target({TYPE, ANNOTATION_TYPE})
@Retention(RUNTIME)
@Constraint(validatedBy = SamePasswordsValidator.class)
@Documented
public @interface SamePasswords {
    String message() default "passwords do not match";
    Class<?>[] groups() default {}; 
    Class<? extends Payload>[] payload() default {};
}

As you can see below, the validator is really simple:

public class SamePasswordsValidator implements ConstraintValidator<SamePasswords, PasswordForm> {

    @Override
    public void initialize(SamePasswords constraintAnnotation) {}

    @Override
    public boolean isValid(PasswordForm value, ConstraintValidatorContext context) {
        if(value.getConfirmedPassword() == null) {
            return true;
        }
        return value.getConfirmedPassword()
                    .equals(value.getPassword());
    }
}

The PasswordForm is just a POJO with some constraint annotations, inclduing the once I have just created:

@SamePasswords
public class PasswordForm {
    @NotBlank
    private String password;
    @NotBlank
    private String confirmedPassword;

    // getters and setters omitted for redability

}

@Controller

The controller has two methods: to display the form and to handle the submission of the form:

@Controller
@RequestMapping("globalerrors")
public class PasswordController {

    @RequestMapping(value = "password")
    public String password(Model model) {
        model.addAttribute(new PasswordForm());
        return "globalerrors/password";
    }

    @RequestMapping(value = "password", method = RequestMethod.POST)
    public String stepTwo(@Valid PasswordForm passwordForm, Errors errors) {
        if (errors.hasErrors()) {
            return "globalerrors/password";
        }
        return "redirect:password";
    }
}

When the password validation fails, a global error is registered in a BindingResult (Errors in the above example) object. We could then display this error on top of the form in a HTML page for example. In Thymeleaf this would be:

<div th:if="${#fields.hasGlobalErrors()}">
  <p th:each="err : ${#fields.globalErrors()}" th:text="${err}">...</p>
</div>

Integration Testing with Spring Test

Let’s setup an integration test:

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = Application.class)
@WebAppConfiguration
public class AccountValidationIntegrationTest {

    @Autowired
    private WebApplicationContext wac;
    private MockMvc mockMvc;

    @Before
    public void setUp() throws Exception {
        mockMvc = MockMvcBuilders.webAppContextSetup(wac).build();
    }
}

The first test verifies that sending a form with empty password and confirmedPassword fails:

    @Test
    public void failsWhenEmptyPasswordsGiven() throws Exception {
        this.mockMvc.perform(post("/globalerrors/password")
                .param("password", "").param("confirmedPassword", ""))
                .andExpect(
                    model().attributeHasFieldErrors(
                        "passwordForm", "password", "confirmedPassword"
                    )
                )
                .andExpect(status().isOk())
                .andExpect(view().name("globalerrors/password"));
    }

In the above example, the test verifies if there are field errors for both password and confirmedPassword fields.

Similarly, I would like to verify that when given passwords do not match, I get a specific, global error. So I would expect something like this: .andExpect(model().hasGlobalError("passwordForm", "passwords do not match")). Unfortunately, ModelResultMatchers returned by MockMvcResultMatchers#model() does not provide methods to assert the given model attribute(s) have global errors

Since it is not there, I created my own matcher that extends from ModelResultMatchers. The Java 8 version of the code is below:

public class GlobalErrorsMatchers extends ModelResultMatchers {

    private GlobalErrorsMatchers() {
    }

    public static GlobalErrorsMatchers globalErrors() {
        return new GlobalErrorsMatchers();
    }

    public ResultMatcher hasGlobalError(String attribute, String expectedMessage) {
        return result -> {
            BindingResult bindingResult = getBindingResult(
                result.getModelAndView(), attribute
            );
            bindingResult.getGlobalErrors()
                .stream()
                .filter(oe -> attribute.equals(oe.getObjectName()))
                .forEach(oe -> assertEquals(
                    "Expected default message", expectedMessage, oe.getDefaultMessage())
                );
        };
    }

    private BindingResult getBindingResult(ModelAndView mav, String name) {
        BindingResult result = (BindingResult) mav.getModel().get(BindingResult.MODEL_KEY_PREFIX + name);
        assertTrue(
            "No BindingResult for attribute: " + name, result != null
        );
        assertTrue(
            "No global errors for attribute: " + name, result.getGlobalErrorCount() > 0
        );
        return result;
    }
}

With the above addition I am now able to verify global validation errors like here below:

import static pl.codeleak.demo.globalerrors.GlobalErrorsMatchers.globalErrors;

@Test
public void failsWithGlobalErrorWhenDifferentPasswordsGiven() throws Exception {
    this.mockMvc.perform(post("/globalerrors/password")
            .param("password", "test").param("confirmedPassword", "other"))
            .andExpect(globalErrors().hasGlobalError(
                "passwordForm", "passwords do not match")
            )
            .andExpect(status().isOk())
            .andExpect(view().name("globalerrors/password"));
}

As you can see extending Spring Test’s matchers and providing you own is relatively easy and can be used to improve validation verification in an integration test.

Resources

The source code for this article can be found here: https://github.com/kolorobot/spring-mvc-beanvalidation11-demo