doNothing void method with params in other class - junit

Question

I currently have 2 classes:
public class aClass{
public void meth1(){
bClass b = new bClass();
b.meth2();// i dont want to call this method
//buss logic
}
}
public class bClass{
public void meth2(){
// some logic
}
}
Currently I am creating a junit test case for the meth1 in the aClass.
However, I don't want to call the meth2 in the bClass, just execute the busslogic in aClass.
The Classes aClass and bClass are fixed - I cannot(and won't) change the code on aClass and bClass.
I tried many things like #injectmock and doNothing using mokito and power mock, but meth2 is always gets called when I am calling meth1 in aClass.
What can I do to fix this?

Answer 1

You can do this with Powermockito. The link explains all the details. Below is how it might look like for your example.
#RunWith(PowerMockRunner.class)
#PrepareForTest(aClass.class)
public class aClassTesting {
#Mock
bClass mockB;
#Test
public void testMeth1(){
//prepare mocks
whenNew(bClass.class).withNoArguments().thenReturn(mockB);
doNothing().when(mockB).meth2();
//run it
aClass instance = new aClass();
aClass.meth1();
//asserts and verify
verifyNew(bClass.class).withNoArguments();
verify(mockB, times(1)).meth2();
}
}
EDIT:
When you mock out the bClass instance using #Mock then it replaces all the methods in that instance with mock methods. If you only want to mock some of the methods in bCLas, then you must spy the bCLass instance instead of mocking it. Spy only mocks the methods you want. So just replace #Mock with #Spy in my example then only meth2 would be blocked but not any other methods in bClass.

Answer 2

As it stands, with the constraint that you cannot change AClass, then the only solution is to use Powermock (or similar tools) as Jose Martinez mentioned above. On its own, Mockito can't replace constructors (which are treated like static method calls), so your only solution is to rewrite aClass.
For any future readers that find this question who don't have that constraint, a quick refactor of bClass will make this much easier to test.
public class aClass{
public void meth1(){
meth1(new bClass());
}
/** Package private for testing. */
public void meth1(bClass b){
b.meth2();
//buss logic
}
}
At this point, you can pass a mock bClass and call the single-parameter overload to test your business logic. You can also move b.meth2() out of the single-parameter method and into the public parameterless method, if it behaves more like a setup call.

Answer 3

You can use the mockito...
public class aClass {
private final bClass b;
public aClass() {
this.b = new bClass()
}
public aClass(bClass b) {
this.b = b;
}
....
}
#RunWith(MockitoJUnitRunner.class)
public class aClassTest {
#Mock
private final bClass b;
#InjectMocks
private aClass a;
....
}