How to fake InitialContext with default constructor

Question

All,

I'm trying to do some unit testing in some archaic java code (no interfaces, no abstraction, etc.)

This is a servlet that uses a ServletContext (which I'm assuming is set up by Tomcat) and it has database information is set up in the web.xml/context.xml file. Now, I've figured out how to make a Fake ServletContext, but the code has

 InitialContext _ic = new InitialContext();

all over the place (so it isn't feasible to replace it). I need to find a way to make a default InitialContext() able to do the _ic.lookup(val) without throwing an exception.

I'm assuming there is some way that the context.xml is getting loaded, but how that magic works, I'm drawing a blank. Anyone have any ideas?

Answer 1

Take advantage of the fact that InitialContext uses an SPI to handle its creation. You can hook into its lifecycle by creating an implementation of javax.naming.spi.InitialContextFactory and passing that to your tests via the system property javax.naming.factory.initial (Context.INTITIAL_CONTEXT_FACTORY). It's simpler than it sounds.

Given this class:

public class UseInitialContext {

    public UseInitialContext() {
        try {
            InitialContext ic = new InitialContext();
            Object myObject = ic.lookup("myObject");
            System.out.println(myObject);
        } catch (NamingException e) {
            e.printStackTrace();
        }
    }


} 

And this impl of InitialContextFactory:

public class MyInitialContextFactory implements InitialContextFactory {

    public Context getInitialContext(Hashtable<?, ?> arg0)
            throws NamingException {

        Context context = Mockito.mock(Context.class);
        Mockito.when(context.lookup("myObject")).thenReturn("This is my object!!");
        return context;
    }
}

Creating an instance of UseInitialContext in a junit test with

-Djava.naming.initial.factory=initial.context.test.MyInitialContext

on the command line outputs This is my object!! (easy to set up in eclipse). I like Mockito for mocking and stubbing. I'd also recommend Micheal Feather's Working Effectively with Legacy Code if you deal with lots of legacy code. It's all about how to find seams in programs in order to isolate specific pieces for testing.