Description: Trying to mock this class (from some library):
public class Signal{
public static Signal fromPool(){
// returns a recycled instance from a signal pool
}
public int getCode(){
// returns some signal code;
}
}
Class Sender uses Signal.fromPool() internally :
public class Sender{
private Signal sig;
public void ready(){
sig = Signal.fromPool();
System.out.println(sig);
}
public void send(OutputStream output){
output.write(sig.getCode());
}
}
And we need to write some unit tests for Sender.
But, In Unit test environment, Signal.fromPool() will fail, because environment lacks some internal dependencies.
Hence, we decide to use "JMockit" to mock Signal class:
public class SenderTest{
// mock signal class
static class MockSignal extends Mockup<Signal>{
@Mock
public static Signal fromPool(){
return new Signal();
}
@Mock
public int getCode(){
return 42;
}
}
@Test
public void testSending(@Mocked OutputStream stream){
// replace Signal with MockSignal
new MockSignal();
// should write 42
new Expectations(){{
stream.write(42);
}};
// test code
Sender sender = new Sender();
sender.ready();
sender.send(stream);
}
}
Problem: Mocked Signal.fromPool returns a null. This statement in above code prints null:
System.out.println(sig);
My understanding is that perhaps inside the mocked fromPool the Mocked class itself isn't being instantiated:
@Mock
public static Signal fromPool(){
return new Signal();
}
How can new Signal return null ? Anyone has a better perspective ?
