error saying expected true, returned false despite setting thenRetun true

[Monica Shiralkar]

I have the below code using Junit and Mockito:

public class Database {

    public boolean isAvailable() {
        return false;
    }
    public int getUniqueId() {
        return 100;
    }
}

public class Service {

    Database database = new Database();

    public Service(Database database) {
        this.database = database;
    }

    public boolean query(String query) {
        return database.isAvailable();
    }


    @Override
    public String toString() {
        return "Using database with id: " + String.valueOf(database.getUniqueId());
    }
}



import static org.junit.jupiter.api.Assertions.assertNotNull;
import static org.junit.jupiter.api.Assertions.assertTrue;
import static org.mockito.Mockito.when;

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.mockito.Mock;
import org.mockito.junit.jupiter.MockitoExtension;

@ExtendWith(MockitoExtension.class)                         
class ServiceTest {

    @Mock
    Database databaseMock;                                  

    @Test
    public void testQuery()  {
        assertNotNull(databaseMock);
        when(databaseMock.isAvailable()).thenReturn(true);  
        Service t  = new Service();             
        boolean check = t.query("* from t");                
        assertTrue(check);
    }
}

It is giving assertion failure. I have set  

when(databaseMock.isAvailable()).thenReturn(true);  

so am expecting that when databaseMock.isAvailable() will be called it will return true but it is returning false and the assertion is failing. Why is it not returning true?
thanks

[Rob Spoor]

Monica Shiralkar wrote:

Service t  = new Service();

How does that even compile, if the Service class has only one constructor that takes a Database? Did you add that constructor after you wrote the test? Because then the Service instance uses its own Database that it creates itself.

[Monica Shiralkar]

Sorry. Below is the code which I am trying (without specifying any constructor )

public class Database {

    public boolean isAvailable() {
        return false;
    }
    public int getUniqueId() {
        return 100;
    }
}

public class Service {

    Database database = new Database();


    public boolean query(String query) {
        return database.isAvailable();
    }


    @Override
    public String toString() {
        return "Using database with id: " + String.valueOf(database.getUniqueId());
    }
}

[Rob Spoor]

So the Service creates and contains its own Database instance. That's not the mock you create.

[Monica Shiralkar]

I was thinking that if we have to mock any method of any class all we have to do is first declare variable of that type with mock annotation like this :

@Mock
Database databaseMock;

And then specify in the when-thenReturns format that when this method is called then return this.

when(databaseMock.isAvailable()).thenReturn(true)

I thought thats all what is required. But now I came to know that that's not all what is required and that's something else is also required apart from this. I will read further and understand what else is required for this.

Thanks.

[Monica Shiralkar]

Found the issue.

My code is simply calling the method using the database object and not the mockDatabase object, and thus not returning based on the mock behaviour (and instead returning false the default value of boolean ).

I added constructor to set this.database = mockObject , then passed the mockObject and it worked as expected.

Thanks.

[Monica Shiralkar]

Is mocking a method call possible if the object on which the mocking method  call is made is not even member variable of that class ?


I had a field like this in the class whose method was being tested :

Database database;

And it was getting set in  constructor like this :

   public Service(Database database) {
       this.database = database;
   }
   

Then we could mock the below call for available method:

   public boolean query(String query) {
       return database.isAvailable();
   }

Is it possible to mock some call if the object using which the external method is called is not even member of the class and thus can't be set using the constructor ?  Or for such case we cannot mock the call at all ?