JUnit: How to test your private methods

Some weeks ago I was creating some unit tests for a hobby project I'm working with. But I found myself stuck trying to test some private methods.

My first though was "Should I even need to test those methods?" I invested some time looking for alternatives, but those methods must be private. What could I do?

One option was to modify those methods to be public, anyway this is a hobby project and I know I'm not going to call them from outside. But since the main reason of this project is to learn I though I would best invest the needed time to find the correct solution.

Being a fan of the Java reflection API, I decided to investigate this approach. This is the result:

/**
* Convenient method to execute private methods from other classes.
* @param test Instance of the class we want to test
* @param methodName Name of the method we want to test
* @param params Arguments we want to pass to the method
* @return Object with the result of the executed method
* @throws Exception
*/
private Object invokePrivateMethod (Object test, String methodName, Object params[]) throws Exception {
   Object ret = null;

   final Method[] methods =
           test.getClass().getDeclaredMethods();
   for (int i = 0; i < methods.length; ++i) {
       if (methods[i].getName().equals(methodName)) {
           methods[i].setAccessible(true);
           ret = methods[i].invoke(test, params);
           break;
       }
   }

   return ret;
}

As you can see the code is simply doing the next steps:

1. Retrieve an array of declared methods
2. Loop the array looking for the method we want to test
3. Once found, set the method as public
4. Execute the method and return the result

And we want to use it, we only need to do something like:

MyClass instance = new MyClass();
String expResult = "Expected Result";
Object[] params = {"A String Value", "Another Value"};
String result = (String) this.invokePrivateMethod(instance, "myPrivateName", params);
assertEquals(expResult, result);

This is the best I could find. Fair enough but, do you know of a better or more elegant solution?

See you soon.