Example of Mockito s argumentCaptor

Question

Can anyone please provide me an example showing how to use the org mockito ArgumentCaptor class and how it is different from simple matchers that are provided with mockito   I read the provided mockito documents but those doesn t illustrate it clearly  none of them are able to explain it with clarity

User · Answer

Here I am giving you a proper example of one callback method . so suppose we have a method like method login() :

 public void login() {
    loginService = new LoginService();
    loginService.login(loginProvider, new LoginListener() {
        @Override
        public void onLoginSuccess() {
            loginService.getresult(true);
        }

        @Override
        public void onLoginFaliure() {
            loginService.getresult(false);

        }
    });
    System.out.print("@@##### get called");
}

I also put all the helper class here to make the example more clear: loginService class

public class LoginService implements Login.getresult{
public void login(LoginProvider loginProvider,LoginListener callback){

    String username  = loginProvider.getUsername();
    String pwd  = loginProvider.getPassword();
    if(username != null && pwd != null){
        callback.onLoginSuccess();
    }else{
        callback.onLoginFaliure();
    }

}

@Override
public void getresult(boolean value) {
    System.out.print("login success"+value);
}}

and we have listener LoginListener as :

interface LoginListener {
void onLoginSuccess();

void onLoginFaliure();

}

now I just wanted to test the method login() of class Login

 @Test
public void loginTest() throws Exception {
    LoginService service = mock(LoginService.class);
    LoginProvider provider = mock(LoginProvider.class);
    whenNew(LoginProvider.class).withNoArguments().thenReturn(provider);
    whenNew(LoginService.class).withNoArguments().thenReturn(service);
    when(provider.getPassword()).thenReturn("pwd");
    when(provider.getUsername()).thenReturn("username");
    login.getLoginDetail("username","password");

    verify(provider).setPassword("password");
    verify(provider).setUsername("username");

    verify(service).login(eq(provider),captor.capture());

    LoginListener listener = captor.getValue();

    listener.onLoginSuccess();

    verify(service).getresult(true);

also dont forget to add annotation above the test class as

@RunWith(PowerMockRunner.class)
@PrepareForTest(Login.class)

User · Answer

I agree with what  fge said  more over  Lets look at example  Consider you have a method   class A       public void foo OtherClass other            SomeData data   new SomeData  Some inner data            other doSomething data             Now if you want to check the inner data you can use the captor      Create a mock of the OtherClass OtherClass other   mock OtherClass class       Run the foo method with the mock new A   foo other       Capture the argument of the doSomething function ArgumentCaptor lt SomeData gt  captor   ArgumentCaptor forClass SomeData class   verify other  times 1   doSomething captor capture         Assert the argument SomeData actual   captor getValue    assertEquals  Some inner data   actual innerData

User · Answer

The steps in order to make a full check are  Prepare the captor   ArgumentCaptor lt SomeArgumentClass gt  someArgumentCaptor   ArgumentCaptor forClass SomeArgumentClass class    verify the call to dependent on component  collaborator of subject under test   times 1  is the default value  so ne need to add it  verify dependentOnComponent  times 1   send someArgumentCaptor capture      Get the argument passed to collaborator SomeArgumentClass someArgument   messageCaptor getValue     someArgument can be used for assertions

User · Answer

The two main differences are    when you capture even a single argument  you are able to make much more elaborate tests on this argument  and with more obvious code  an ArgumentCaptor can capture more than once    To illustrate the latter  say you have   final ArgumentCaptor lt Foo gt  captor   ArgumentCaptor forClass Foo class    verify x  times 4   someMethod captor capture        for instance   Then the captor will be able to give you access to all 4 arguments  which you can then perform assertions on separately   This or any number of arguments in fact  since a VerificationMode is not limited to a fixed number of invocations  in any event  the captor will give you access to all of them  if you wish   This also has the benefit that such tests are  imho  much easier to write than having to implement your own ArgumentMatchers -- particularly if you combine mockito with assertj   Oh  and please consider using TestNG instead of JUnit

[java] Example of Mockito's argumentCaptor

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