Mockito Unit test: Factory create newInstance

Question

For unit testing I want to test good and bad scenario's

I'm getting a bit stuck on the Factory.createFoo() method. How do I write proper unit tests for this (with Mockito)

public class Bar extends Foo {
    public Bar() {}
    public Bar(Scenario scenario){
       ...DoStuff..
    }
}

public static <T extends Foo> T createFoo(Class<T> fooClass) throws RuntimeException {
    try {
        return fooClass.newInstance();
    } catch (InstantiationException | IllegalAccessException | NoSuchMethodException | InvocationTargetException e) {
        throw new RuntimeException("Could not create the Foo: " + fooClass.getSimpleName(), e);
    }
}

public static <T extends Foo> T createFoo(Scenario scenario, Class<T> fooClass) throws RuntimeException {
    try {
        return fooClass.getDeclaredConstructor(Scenario.class).newInstance(scenario);
    } catch (InstantiationException | IllegalAccessException | NoSuchMethodException | InvocationTargetException e) {
        throw new RuntimeException("Could not create the needed Foo: " + fooClass.getSimpleName(), e);
    }
}

I would like to be able to mock the following parts:

fooClass.newInstance();

fooClass.getDeclaredConstructor(Scenario.class).newInstance(scenario);

I've found some factory examples, but all without the generic

Class<T>

making those examples invalid for me.

How to proceed to test these kind of factory methods? If there is a design flaw that is making this non testable, don't hesitate to point me those flaws ;-)

Personally I would not mock those methods, because that is basic Java.lang. I think it's totally fine, to test if the factory method returns an instance of an object that is equal to new T() for instance. — Christian Ziegler, May 16 '17 at 13:00
How do i get then in the catch? as for now it's always working. — W vd L, May 16 '17 at 13:01
Yes sorry, I just noticed I missed that. Let me see if I can get something working. — Christian Ziegler, May 16 '17 at 13:02
Check this: http://stackoverflow.com/questions/14292863/how-to-mock-a-final-class-with-mockito — Christian Ziegler, May 16 '17 at 13:14
That link aint helping me :( as far i checked it i still can't spy on/mock the fooClass.newInstance() — W vd L, May 16 '17 at 14:07
Rather than mocking, would it not be easier set up a test with real classes that will cause the required exceptions to be thrown? Example: To get an InstantiationException you can pass in an abstract class (defined as a nested class inside your test) and to get an IllegalAccessException you can send in a class with a private no-args constructor. Then test if RuntimeException was thrown. — mdewit, May 16 '17 at 14:23
@mdewit if you post your comment as reply, i can flag it as the right answer, as it is imo closer to the real-life-scenario and more elegant as mocking could be — W vd L, May 17 '17 at 08:00

score 0 · Accepted Answer · answered May 17 '17 at 08:10

0

Rather than mocking, would it not be easier set up a test with real classes that will cause the required exceptions to be thrown?

Example: To get an InstantiationException you can pass in an abstract class (defined as a nested class inside your test) and to get an IllegalAccessException you can send in a class with a private no-args constructor. Then test if RuntimeException was thrown.

answered May 17 '17 at 08:10

mdewit

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Mockito Unit test: Factory create newInstance

1 Answers1