How to JUnit test that two List<E> contain the same elements in the same order?

Question

Context

I am writing a simple JUnit test for the MyObject class.

A MyObject can be created from a static factory method that takes a varargs of String.

MyObject.ofComponents("Uno", "Dos", "Tres");

At any time during the existence of MyObject, clients can inspect the parameters it was created by in the form of a List<E>, through the .getComponents() method.

myObject.ofComponents(); // -> List<String>: { "Uno", "Dos", "Tres" }

In other words, a MyObject both remembers and exposes the list of parameters that brought it into existence. More details about this contract:

• The order of getComponents will be the same as the one chosen for object creation
• Duplicate subsequent String components are allowed and retained in order
• Behaviour on null is undefined (other code guarantees no null gets to the factory)
• There are no ways to alter the list of components after object instantiation

I am writing a simple test that creates a MyObject from a list of String and checks that it can return the same list via .getComponents(). I do this immediately but this is supposed to happen at a distance in a realistic code path.

Code

Here my attempt:

---

List<String> argumentComponents = Lists.newArrayList("One", "Two", "Three");
List<String> returnedComponents =
    MyObject.ofComponents(
        argumentComponents.toArray(new String[argumentComponents.size()]))
        .getComponents();
assertTrue(Iterables.elementsEqual(argumentComponents, returnedComponents));

---

Question

• Is Google Guava Iterables.elementsEqual() the best way, provided I have the library in my build path, to compare those two lists? this is something I have been agonizing about; should I use this helper method which goes over an Iterable<E>.. check size and then iterate running .equals().. or any other of the methods that an Internet search suggests? what's the canonical way to compare lists for unit tests?

Optional insights I would love to get

• Is the method test designed reasonably? I am not an expert in JUnit!
• Is .toArray() the best way to convert a List<E> to a varargs of E?

Answer 1

Why not simply use List#equals?

assertEquals(argumentComponents, imapPathComponents);

Contract of List#equals:

two lists are defined to be equal if they contain the same elements in the same order.