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Is there any way to Mock the private method , which is there in other class

As per my knowledge, We can Mock the private method in same class by using PowerMockito.
With in the same class is working fine for me , but when i'm calling private method from the other class it's not working.
Below Example i've 2 classes , Service class and Helper classes
Helper class having private method.
#RunWith(PowerMockRunner.class)
#PrepareForTest({ Helper.class,Service.class })
#PowerMockIgnore("javax.management.*")
public class EPartnerBatchServiceTest {
private Helper helper;
#InjectMocks
private ServiceClass serviceClass;
#Before
public void setUp() throws Exception {
helper = PowerMockito.spy(new Helper());
ServiceClass = PowerMockito.spy(new serviceClass());
MockitoAnnotations.initMocks(this);
}
#Test
public void testUpdateIndividualUserStatus() throws Exception {
PowerMockito.doReturn("Test").when(helper, "privateMethod", anyString(), Matchers.anyObject());
String response = serviceClass.update(loggerId, activityLogDTO);
}
}
Sample Classes :
Class A{
value=new B().method1();
}
Class B{
public method1(){
value = method2();
}
private method2(){
return "Test";
}
}

You shouldn't be worrying with testing explicitly your private methods, since they are not accessible for the ones calling it, it's function should be tested somewhere in the flow of your public methods. But, if for some reason you need to test them explicitly, then maybe reflections and setting those methods as accessible for testing may resolve your problem.
You'll find great examples here: https://www.baeldung.com/java-method-reflection

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.

Providing context for #Value fields from a unit test

I have a class like this:
#Service("someClient")
public class SomeClient {
#Value{some.value}
private String someValue;
public void someMethod() {
return someValue;
}
}
And a test like this:
#ContextConfiguration(locations = "classpath:/some/where/testApplicationContext.xml")
#RunWith(SpringJUnit4ClassRunner.class)
public class SomeClientTest extends TestCase {
#Value{some.value}
private String someValueTest;
#Test
public void shouldWork() {
...
someClient.someMethod()
...
}
}
When the wider application is running, the field someValue inside the SomeClient class is populated from a properties file referenced from testApplicationContext.xml. When I run the test in debug mode I can see that someValueTest is populated in the test, but when the test calls the class under test, the value is not populated.
I could use some advice! Obviously I can change the visibility of the field in the class, or provide a setter, however I would like to avoid that if possible. If it isn't, please advise.

In order to populate fields with #Value annotation in your test you need to configure PropertySourcesPlaceholderConfigurer.
Add the following to your test:
#Configuration
public static class Config {
#Bean
public static PropertySourcesPlaceholderConfigurer propertyConfigurer() {
return new PropertySourcesPlaceholderConfigurer();
}
}
To read the values from test property file you can add
#TestPropertySource(locations="classpath:test.properties") to your Test class declaration

You can use ReflectionTestUtils from org.springframework.test.util.ReflectionTestUtils package to mock any variable, including the ones that access the properties file.
#RunWith(SpringJUnit4ClassRunner.class)
public class SomeClientTest extends TestCase {
private SomeClient someClient;
#Test
public void shouldWork() {
//Initialize someClient
someClient = new SomeClient();
ReflectionTestUtils.setField(someClient, "variable name", "the variable value");
someClient.someMethod()
...
}
}

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
}
}