java - Mock creation of Object inside method -

problem description

i'm trying mock object creation inside of method. have loginfragment creating loginpresenterimpl inside of oncreate method, shown below:

public class loginfragment extends basefragment {     private loginpresenter mpresenter;      @override     public void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);          mpresenter = new loginpresenterimpl(this); <<-- should mocked     }  } 

i have problems combining robolectricgradletestrunner , powermockrunner in 1 test after reading this post, found way how that, test this:

baserobolectrictest.java

@runwith(powermockrunner.class) @powermockrunnerdelegate(robolectricgradletestrunner.class) @config(constants = buildconfig.class, sdk = 21) @powermockignore({"org.mockito.*", "org.robolectric.*", "android.*"}) public abstract class baserobolectrictest {  } 

test.java

@preparefortest({loginpresenterimpl.class}) public class test extends baserobolectrictest  {      private loginpresenterimpl mpresentermock;      @rule     public powermockrule rule = new powermockrule();      @before     public void setup() {         mockstatic(loginpresenterimpl.class);          mpresentermock = powermockito.mock(loginpresenterimpl.class);     }      @test     public void testing() throws exception {         when(mpresentermock.loadusername(any(context.class))).thenreturn(valid_username);         when(mpresentermock.loadpassword(any(context.class))).thenreturn(valid_password);         when(mpresentermock.canautologin(valid_username, valid_password)).thenreturn(true);          whennew(loginpresenterimpl.class).withanyarguments().thenreturn(mpresentermock);          fragmenttestutil.startfragment(createloginfragment());     }      private loginfragment createloginfragment() {         loginfragment loginfragment = loginfragment.newinstance();         return loginfragment;     } } 

this bad code , opposite of "dependency injection" pattern.

if used dependency injection framework dagger, such problem wouldn't happen used classed injected.

in test cases override modules provide mocks instead of real classes:

@module public class testdatamodule extends datamodule {      public testdatamodule(application application) {         super(application);     }      @override     public databasemanager providedatabasemanager(databaseutil databaseutil) {         return mock(databasemanager.class);     } } 

and mock behavior.

solid rules important in mainaining testable , reusable code.