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Spring Boot #RestController #Autowired null in Unit tests

I can't understand why #Autowiring my #RestController class is returning null.
I want to do a basic unit test before doing an integrated test but its failing.
In fact anything that is being #Autowired is showing null in the test package.
I have a very simple test, I just want to see the basic works:
A very simple example:
#Component
public class SimpleComponent {
public int add(int a, int b){
return a + b;
}
}
And the test:
class SimpleComponentTest {
#Autowired
private SimpleComponent component;
#Test
public void givenSimpleComponentShouldNotBeNull(){
assertNotNull(component);//How on earth does this fail?
}
}
Here is the code from the Controller class:
#RestController
public class EmployeeAccountApi {
#PostMapping("/register")
public String register(){
return "Registering!";
}
}
public class EmployeeAccountApiUnitTest {
#Autowired
private EmployeeAccountApi employeeAccountApi;
#Test
public void testAutowiring(){
assertNotNull(employeeAccountApi);//Fails, Can't understand why
}
}
This works with the #Mock annotation:
But I dont want to mock it as that is the class I am unit testing.
I want to test that the method returns a basic string.
Question is why isn't it working?
#ExtendWith(MockitoExtension.class)
public class EmployeeAccountApiUnitTest {
#Mock
private EmployeeAccountApi employeeAccountApi;
#Test
public void testAutowiring(){
assertNotNull(employeeAccountApi);//This works
}
}
Even if I get the Employee Service that clearly worked and tested in the previous test also is null in this class:
public class EmployeeAccountApiUnitTest {
#Autowired
private EmployeeAccountApi employeeAccountApi;
#Autowired
private EmployeeService service;
#Test
public void testAutowiring(){
//assertNotNull(employeeAccountApi);
assertNotNull(service);
}
}
Why is #Autowired null in the Test?
Mocking is working fine
Plenty of similar questions but they are too specific and not provide any basic information

#Autowired only works if you are spinning up the application context for your application. Annotate the test class with #SpringBootTest, which tells the test to start the entire spring application context, and it should work.

#SpringBootTest has to be used on the test class for Spring to load your ApplicationContext and wire things up. Without out this there's nothing for Spring to inject.
You can use #WebMvcTest on the test class to focus your tests only on the Web Layer.
There's a whole bunch of annotations that allow you to "slice" your ApplicationContext up lots of other ways for testing various other parts of your application.
Spring's documentation and tutorials are really very good. You should check them out.
Testing the Web Layer

Feign client unit test

I would like to know what is the best way to write unit tests in this context :
MyApi :
#RestController
public class MyApi{
#Autowired
MyAction myAction;
#PostMapping
public ResponseEntity addAction(#ResponseBody MyDto myDto){
return myAction.addAction(myDto);
}
}
MyAction :
#Service
public class MyAction{
#Autowired
private MyClient myClient;
public ResponseEntity<AuthenticationResponseDto> login(MyDto myDto{
return ResponseEntity.ok(myClient.addClient(myDto));
}
}
For example, is it mandatory to add constructor ?
Thanks

It's considered a good practice to use constructor injection, however if you don't want to use it you need to use #Mock and #InjectMocks. It uses reflection and constructor is not required to be defined.
#RunWith(MockitoJUnitRunner.class)
public class Test {
#Mock
private Client client;
#InjectMocks
private ServiceImpl plannerService = new ServiceImpl();
#Test
public void test() throws Exception {
....
}
}

I'm sure there is a way to avoid using an autowired constructor and just autowiring a field, however I use constructors as I consider it a good practice. It also makes it easy to inject a mocked object like so
#Mock
MyAction myAction;
MyApi myApi;
ResponseEntity<AuthenticationResponseDto> testResponse = ResponseEntity.ok
(new AuthenticationResponseDto());
#Before
public void setup(){
myApi = new MyApi(myAction);
}
#Test
public void simpleMyApiTestExample (){
when(myAction.login(any())).thenAnswer(i-> testRespone);
ResponseEntity<?> actualResponse = myApi.addAction(new MyDto());
assertThat(actualResponse).isSameAs(testResponse);
}
Just to give you an idea. I just wrote this example in the SO text editor, so appologies for any typos/mistakes. But hopefully this shows why having constructors is useful for testing things that are autowired. It allows you to mock the objects necessary for instantiation by adding them to the constructor. In this example this would probably also apply to MyDto and AuthenticationResponseDto objects as well.

Unit test of Spring boot service with private fields and #PostConstruct

I have a Spring boot service defined like this
#Service
public class MyService {
private String field1;
private String field2;
#Autowired
private AnotherService anotherService
#PostConstruct
public void init() {
anotherService.initField1(field1);
anotherService.initField2(field2);
}
public String foo() {
return field1 + field2;
}
}
How should I write a unit test for foo. Well, it's more about how to deal with class fields and the PostConstruct methods.
Thanks!!
EDIT:
Added AnotherService as a field as well.

The following example shows a #Service Bean that uses constructor injection to obtain a required AnotherService bean:
#Service
public class MyService {
private String field1;
private String field2;
private final AnotherService anotherService;
public MyService(AnotherService anotherService) {
this.anotherService = anotherService;
this.anotherService.initField1(field1);
this.anotherService.initField2(field2);
}
public String foo() {
return field1 + field2;
}
}
Note you can omit the #Autowired becuase MyService has one constructor. See here for more info.
testing with Spring
Use the #RunWith(SpringRunner.class) and #SpringBootTest to inject MyService and start using it:
#RunWith(SpringRunner.class)
#SpringBootTest
public class MyServiceTest {
#Autowired
private MyService service;
#Test
public void testFoo() {
String expResult = "";
String result = service.foo();
assertEquals(expResult, result);
}
}
testing without Spring
public class MyServiceTest2 {
private MyService service;
#Before
public void setUp() {
service = new MyService(new AnotherService.Fake());
}
#Test
public void testFoo() {
String expResult = "";
String result = service.foo();
assertEquals(expResult, result);
}
}
Here Fake is a fake implementation of the AnotherService interface which allows you to have a pure unit test.

Writing good, testable code can be hard. There are some pitfalls waiting for everyone to fall into sooner or later.
As a rule of thumb, try to avoid field level injection, use constructor parameter injection instead:
#Service
public class MyService {
private AnotherService anotherService;
#Autowired
MyService (AnotherService anotherService) {
this.anotherService = anotherService;
}
}
This is the cleanest solution. You can call the constructor from your tests, spring will inject dependencies the same way at runtime. So there is no difference to deal with.
The same goes for any life cycle constructs like #PostConstruct. If you can avoid them, do it. Let the constructor handle it. If you absolutely have to keep them around, well, the only logical solution is to manually call them from your test code.
Now, how to setup services that at runtime would be autowired by the container?
For unit testing, you basically have three options (in no particular order):
If the required service is rather simple and can easily be constructed, create and pass it as the framework would do.
If the service has a limited interface that does not change too often, create a fake service.
Use a mocking lib like mockito (spring-boot-test provides it by default).

Best practice - Setting a field without setters in a unit test

Let's say you have the following class you would like to test:
public class SomeService {
public String someMethod(SomeEntity someEntity) {
return someEntity.getSomeProperty();
}
}
The SomeEntity looks like this:
public class SomeEntity {
private String someProperty;
public getSomeProperty() {
return this.someProperty;
}
}
The assertion you would like to do can be the following:
String result = someService.someMethod(someEntity);
assertThat(result).isEqualTo("someValue");
How can you make this test work?
1) Add a setter for 'someProperty' in the SomeEntity class. I don't think this a good solution because you don't change production code to make your tests work.
2) Use ReflectionUtils to set the value of this field. Test would look like this:
public class TestClass {
private SomeService someService;
#Test
public void testSomeProperty() {
SomeEntity someEntity = new SomeEntity();
ReflectionTestUtils.setField(someEntity, "someProperty", "someValue");
String result = someService.someMethod(someEntity);
assertThat(result).isEqualTo("someValue");
}
}
3) You create an inner class in your test class that extends the SomeEntity class and adds the setter for this field. However, for this to work you will also need to change the SomeEntity class because the field should become 'protected' instead of 'private'. Test class might look like this:
public class TestClass {
private SomeService someService;
#Test
public void testSomeProperty() {
SomeEntityWithSetters someEntity = new SomeEntityTestWithSetters();
someEntity.setSomeProperty("someValue");
String result = someService.someMethod(someEntity);
assertThat(result).isEqualTo("someValue");
}
public class SomeEntityWithSetters extends SomeEntity {
public setSomeProperty(String someProperty) {
this.someProperty = someProperty;
}
}
}
4) You use Mockito to mock SomeEntity. Seems fine if you only need to mock only one property in the class, but what if you need to mock like 10 properties are so. The test might look like this:
public class TestClass {
private SomeService someService;
#Test
public void testSomeProperty() {
SomeEntity someEntity = mock(SomeEntity.class);
when(someEntity.getSomeProperty()).thenReturn("someValue");
String result = someService.someMethod(someEntity);
assertThat(result).isEqualTo("someValue");
}
}

you can set the value using reflection. It doesn't need any change in production code.
ReflectionTestUtils.setField(YourClass.class, "fieldName", fieldValue);

You can add a setter with default (package private) scope.

With junit testing of SomeService.someMethod()
alternative 1. should not use this as no need to change entity for writing junit.
alternative 2. can be used.
alternative 3. again same a 3, no need to extend for just junit. how about when the class cannot be extended.
alternative 4. yes, a good option. mockito is being used for the same reason.

What is the behavior / contract specific to SomeService that is testable? Based upon your skeletal code, there really isn't any. It will either throw a NPE on bad input, or return a String that may or may not be null, depending on Hibernate magic. Not sure what you can actually test.

I have been through this same dilemma many times before, a quick solution is to make the field you want to mock package protected, or provide a protected setter. Of course both will alter production code.
Alternatively, you can consider dependency injection framework, such as Dagger. Below is an example they give:
#Module
class DripCoffeeModule {
#Provides Heater provideHeater(Executor executor) {
return new CpuHeater(executor);
}
}
This JUnit test overrides DripCoffeeModule's binding for Heater with a mock object from Mockito. The mock gets injected into the CoffeeMaker and also into the test.
public class CoffeeMakerTest {
#Inject CoffeeMaker coffeeMaker;
#Inject Heater heater;
#Before public void setUp() {
ObjectGraph.create(new TestModule()).inject(this);
}
#Module(
includes = DripCoffeeModule.class,
injects = CoffeeMakerTest.class,
overrides = true
)
static class TestModule {
#Provides #Singleton Heater provideHeater() {
return Mockito.mock(Heater.class);
}
}
#Test public void testHeaterIsTurnedOnAndThenOff() {
Mockito.when(heater.isHot()).thenReturn(true);
coffeeMaker.brew();
Mockito.verify(heater, Mockito.times(1)).on();
Mockito.verify(heater, Mockito.times(1)).off();
}
}

Injecting #Autowired private field during testing

I have a component setup that is essentially a launcher for an application. It is configured like so:
#Component
public class MyLauncher {
#Autowired
MyService myService;
//other methods
}
MyService is annotated with the #Service Spring annotation and is autowired into my launcher class without any issues.
I would like to write some jUnit test cases for MyLauncher, to do so I started a class like this:
public class MyLauncherTest
private MyLauncher myLauncher = new MyLauncher();
#Test
public void someTest() {
}
}
Can I create a Mock object for MyService and inject it into myLauncher in my test class? I currently don't have a getter or setter in myLauncher as Spring is handling the autowiring. If possible, I'd like to not have to add getters and setters. Can I tell the test case to inject a mock object into the autowired variable using an #Before init method?
If I'm going about this completely wrong, feel free to say that. I'm still new to this. My main goal is to just have some Java code or annotation that puts a mock object in that #Autowired variable without me having to write a setter method or having to use an applicationContext-test.xml file. I would much rather maintain everything for the test cases in the .java file instead of having to maintain a separate application content just for my tests.
I am hoping to use Mockito for the mock objects. In the past I have done this by using org.mockito.Mockito and creating my objects with Mockito.mock(MyClass.class).

You can absolutely inject mocks on MyLauncher in your test. I am sure if you show what mocking framework you are using someone would be quick to provide an answer. With mockito I would look into using #RunWith(MockitoJUnitRunner.class) and using annotations for myLauncher. It would look something like what is below.
#RunWith(MockitoJUnitRunner.class)
public class MyLauncherTest
#InjectMocks
private MyLauncher myLauncher = new MyLauncher();
#Mock
private MyService myService;
#Test
public void someTest() {
}
}

The accepted answer (use MockitoJUnitRunner and #InjectMocks) is great. But if you want something a little more lightweight (no special JUnit runner), and less "magical" (more transparent) especially for occasional use, you could just set the private fields directly using introspection.
If you use Spring, you already have a utility class for this : org.springframework.test.util.ReflectionTestUtils
The use is quite straightforward :
ReflectionTestUtils.setField(myLauncher, "myService", myService);
The first argument is your target bean, the second is the name of the (usually private) field, and the last is the value to inject.
If you don't use Spring, it is quite trivial to implement such a utility method. Here is the code I used before I found this Spring class :
public static void setPrivateField(Object target, String fieldName, Object value){
try{
Field privateField = target.getClass().getDeclaredField(fieldName);
privateField.setAccessible(true);
privateField.set(target, value);
}catch(Exception e){
throw new RuntimeException(e);
}
}

Sometimes you can refactor your #Component to use constructor or setter based injection to setup your testcase (you can and still rely on #Autowired). Now, you can create your test entirely without a mocking framework by implementing test stubs instead (e.g. Martin Fowler's MailServiceStub):
#Component
public class MyLauncher {
private MyService myService;
#Autowired
MyLauncher(MyService myService) {
this.myService = myService;
}
// other methods
}
public class MyServiceStub implements MyService {
// ...
}
public class MyLauncherTest
private MyLauncher myLauncher;
private MyServiceStub myServiceStub;
#Before
public void setUp() {
myServiceStub = new MyServiceStub();
myLauncher = new MyLauncher(myServiceStub);
}
#Test
public void someTest() {
}
}
This technique especially useful if the test and the class under test is located in the same package because then you can use the default, package-private access modifier to prevent other classes from accessing it. Note that you can still have your production code in src/main/java but your tests in src/main/test directories.
If you like Mockito then you will appreciate the MockitoJUnitRunner. It allows you to do "magic" things like #Manuel showed you:
#RunWith(MockitoJUnitRunner.class)
public class MyLauncherTest
#InjectMocks
private MyLauncher myLauncher; // no need to call the constructor
#Mock
private MyService myService;
#Test
public void someTest() {
}
}
Alternatively, you can use the default JUnit runner and call the MockitoAnnotations.initMocks() in a setUp() method to let Mockito initialize the annotated values. You can find more information in the javadoc of #InjectMocks and in a blog post that I have written.

I believe in order to have auto-wiring work on your MyLauncher class (for myService), you will need to let Spring initialize it instead of calling the constructor, by auto-wiring myLauncher. Once that is being auto-wired (and myService is also getting auto-wired), Spring (1.4.0 and up) provides a #MockBean annotation you can put in your test. This will replace a matching single beans in context with a mock of that type. You can then further define what mocking you want, in a #Before method.
public class MyLauncherTest
#MockBean
private MyService myService;
#Autowired
private MyLauncher myLauncher;
#Before
private void setupMockBean() {
doNothing().when(myService).someVoidMethod();
doReturn("Some Value").when(myService).someStringMethod();
}
#Test
public void someTest() {
myLauncher.doSomething();
}
}
Your MyLauncher class can then remain unmodified, and your MyService bean will be a mock whose methods return values as you defined:
#Component
public class MyLauncher {
#Autowired
MyService myService;
public void doSomething() {
myService.someVoidMethod();
myService.someMethodThatCallsSomeStringMethod();
}
//other methods
}
A couple advantages of this over other methods mentioned is that:
You don't need to manually inject myService.
You don't need use the Mockito runner or rules.

I'm a new user for Spring. I found a different solution for this. Using reflection and making public necessary fields and assign mock objects.
This is my auth controller and it has some Autowired private properties.
#RestController
public class AuthController {
#Autowired
private UsersDAOInterface usersDao;
#Autowired
private TokensDAOInterface tokensDao;
#RequestMapping(path = "/auth/getToken", method = RequestMethod.POST)
public #ResponseBody Object getToken(#RequestParam String username,
#RequestParam String password) {
User user = usersDao.getLoginUser(username, password);
if (user == null)
return new ErrorResult("Kullanıcıadı veya şifre hatalı");
Token token = new Token();
token.setTokenId("aergaerg");
token.setUserId(1);
token.setInsertDatetime(new Date());
return token;
}
}
And this is my Junit test for AuthController. I'm making public needed private properties and assign mock objects to them and rock :)
public class AuthControllerTest {
#Test
public void getToken() {
try {
UsersDAO mockUsersDao = mock(UsersDAO.class);
TokensDAO mockTokensDao = mock(TokensDAO.class);
User dummyUser = new User();
dummyUser.setId(10);
dummyUser.setUsername("nixarsoft");
dummyUser.setTopId(0);
when(mockUsersDao.getLoginUser(Matchers.anyString(), Matchers.anyString())) //
.thenReturn(dummyUser);
AuthController ctrl = new AuthController();
Field usersDaoField = ctrl.getClass().getDeclaredField("usersDao");
usersDaoField.setAccessible(true);
usersDaoField.set(ctrl, mockUsersDao);
Field tokensDaoField = ctrl.getClass().getDeclaredField("tokensDao");
tokensDaoField.setAccessible(true);
tokensDaoField.set(ctrl, mockTokensDao);
Token t = (Token) ctrl.getToken("test", "aergaeg");
Assert.assertNotNull(t);
} catch (Exception ex) {
System.out.println(ex);
}
}
}
I don't know advantages and disadvantages for this way but this is working. This technic has a little bit more code but these codes can be seperated by different methods etc. There are more good answers for this question but I want to point to different solution. Sorry for my bad english. Have a good java to everybody :)

Look at this link
Then write your test case as
#RunWith(SpringJUnit4ClassRunner.class)
#ContextConfiguration({"/applicationContext.xml"})
public class MyLauncherTest{
#Resource
private MyLauncher myLauncher ;
#Test
public void someTest() {
//test code
}
}