Spring-Boot UnitTest: #Value in ConstraintValidator - spring-boot

Question

I'm currently providing coverage - testing the validation of my DTO through MockMVC request call.
I recently introduced a new field in my Registration ConstraintValidator, supportedSpecializations, of which I inject the values from application.properties for easy maintenance and expandability. see code fragment below:
#Component
public class RegistrationValidator implements ConstraintValidator<Registration, String> {
//campus.students.supportedspecializations="J2E,.NET,OracleDB,MySQL,Angular"
#Value("${campus.students.supportedspecializations}")
private String supportedSpecializations;
private String specializationExceptionMessage;
//All ExceptionMessages are maintained in a separate class
#Override
public void initialize(Registration constraintAnnotation) {
exceptionMessage = constraintAnnotation.regionException().getMessage();
}
#Override
public boolean isValid(RegistrationData regData, ConstraintValidatorContext context) {
String[] specializations = supportedSpecializations.split(",");
boolean isValidSpecialization = Arrays.stream(specializations)
.anyMatch(spec -> spec.equalsIgnoreCase(regData.getSpec()));
if (!isValidSpecialization){
context.disableDefaultConstraintViolation();
context.buildConstraintViolationWithTemplate(specializationExceptionMessage)
.addConstraintViolation();
return false;
}
//additional validation logic...
return true;
}
}
Unit tests now fail due to the field not being injected by the defined property of the #Value annotation.
I'm not sure if ReflectionTestUtils could help in my case, so any suggestions are greatly appreciated about how to inject the required values in UnitTests.
Spring version is 2.1.0
I'm currently testing with the following snippet:
#InjectMocks
private StudentController mockRestController;
#Mock
private StudentService mockStudentService;
#Mock
private ValidationExceptionTranslator mockExceptionTranslator;
#Value("${campus.students.supportedspecializations}")
private String supportedSpecializations;
private MockMvc mockMvc;
private static final String VALIDATION_SUCCESSFUL = "success";
private static final String VALIDATION_FAILED = "failed";
#Before
public void setup() {
MockitoAnnotations.initMocks(this);
this.mockMvc = MockMvcBuilders.standaloneSetup(mockRestController).build();
doReturn(
ResponseEntity.status(HttpStatus.OK)
.header("Content-Type", "text/html; charset=utf-8")
.body(VALIDATION_SUCCESSFUL))
.when(mockStudentService).insertStudent(Mockito.any());
doReturn(
ResponseEntity.status(HttpStatus.BAD_REQUEST)
.header("Content-Type", "application/json")
.body(VALIDATION_FAILED))
.when(mockExceptionTranslator).translate(Mockito.any());
}
#Test
public void testValidation_UnsupportedSpecialization() throws Exception {
MvcResult mvcResult = mockMvc.perform(
post("/Students").contentType(MediaType.APPLICATION_JSON_UTF8).content(
"{\"registrationData\":{\"spec\":\"unsupported\"}}"))
.andExpect(status().isBadRequest())
.andReturn();
assertEquals(VALIDATION_FAILED, mvcResult.getResponse().getContentAsString());
verify(mockExceptionTranslator, times(1)).translate(Mockito.any());
verify(mockStudentService, times(0)).insertStudent(Mockito.any());
}
I tried annotating my Test class with #RunWith(SpringRunner.class) and #SpringBootTest(classes = Application.class), but the validation test still fails due to #Value not being resolved. I might be wrong but I think the ConstraintValidator's instance is created before we reach the restController, so a MockMVC perform(...) call couldn't simply just make sure the appropriate #Value in the validator gets injected into supportedSpecializations.

Answer 1

Solved the issue the following way:
Added the following annotations to the Test Class
#RunWith(SpringRunner.class)
#SpringBootTest(classes = Application.class)
#AutoConfigureMockMvc
Then autowired the controller and mockMVC, finally annotated service and translator with Spring's #MockBean
So currently it looks something like this:
#RunWith(SpringRunner.class)
#SpringBootTest(classes = Application.class)
#AutoConfigureMockMvc
public class StudentValidatorTest {
#Autowired
private StudentController mockRestController;
#MockBean
private StudentService mockStudentService;
#MockBean
private ValidationExceptionTranslator mockExceptionTranslator;
#Autowired
private MockMvc mockMvc;
private static final String VALIDATION_SUCCESSFUL = "success";
private static final String VALIDATION_FAILED = "failed";
#Before
public void setup() {
MockitoAnnotations.initMocks(this);
this.mockMvc = MockMvcBuilders.standaloneSetup(mockRestController).build();
doReturn(
ResponseEntity.status(HttpStatus.OK)
.header("Content-Type", "text/html; charset=utf-8")
.body(VALIDATION_SUCCESSFUL))
.when(mockStudentService).insertStudent(Mockito.any());
doReturn(
ResponseEntity.status(HttpStatus.BAD_REQUEST)
.header("Content-Type", "application/json")
.body(VALIDATION_FAILED))
.when(mockExceptionTranslator).translate(Mockito.any());
}
//...and tests...

Answer 2

Yes,
use ReflectionTestUtil.
Use ReflectionTestUtil.setField to set the value of supportedSpecializationsin the
setup() method (junit < 1.4)
or in the #Before annotated method (junit > 1.4) in your unit test.
More Details
I recommend against using MockMVC for your unit tests;
it is fine for integration tests,
just not unit tests.
There is no need to start Spring for a Unit Test;
you never need Spring to perform injections for your unit tests.
Instead,
instantiate the class you are testing and call the methods directly.
Here is a simple example:
public class TestRegistrationValidator
{
private static final String VALUE_EXCEPTION_MESSAGE = "VALUE_EXCEPTION_MESSAGE";
private static final String VALUE_SUPPORTED_SPECIALIZATIONS = "BLAMMY,KAPOW";
private RegistrationValidator classToTest;
#Mock
private Registration mockRegistration;
#Mock
private RegionExceptionType mockRegionExceptionType; // use the actual type of regionExcpeption.
#Before
public void preTestSetup()
{
MockitoAnnotations.initMocks(this);
ReflectionTestUtils.setField(classToTest, "supportedSpecializations", VALUE_SUPPORTED_SPECIALIZATIONS);
doReturn(VALUE_EXCEPTION_MESSAGE).when(mockRegionExceptionType).getMessage();
doReturn(mockRegionExceptionType).when(mockRegion).regionException();
}
#Test
public void initialize_allGood_success()
{
classToTest.initialize(mockRegistration);
...assert some stuff.
...perhaps verify some stuff.
}
}

Answer 3

The best option i think for you is to use constructor injection in your RegistrationValidator.class , so that you can assign mock or test values directly for testing as well when required. Example :
#Component
class ExampleClass {
final String text
// Use #Autowired to get #Value to work.
#Autowired
ExampleClass(
// Refer to configuration property
// app.message.text to set value for
// constructor argument message.
#Value('${app.message.text}') final String text) {
this.text = text
}
}
This way you can set your mock values to the variables for unit testing.
Yes, you are right a custom constructor is not an option here, then you could introduce a configuration class where you have these values read from yml or property and autowire that in the validator .That should work for you.
Or
You can provide the #Value properties in a separate test.yml or test.properties and specify that to be taken up while running your integrated tests. In that case you should be able to resolve these values.
#RunWith(SpringJUnit4ClassRunner.class)
#SpringApplicationConfiguration(classes = ExampleApplication.class)
#TestPropertySource(locations="classpath:test.properties")
public class ExampleApplicationTests {
}
The #TestPropertySource annotation has higher precedence order and it should resolve your values.