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

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

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  amp  amp  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

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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