How to check if an array is one of the elements in a two-dimensional array

Question

I am trying to assert that an array of string elements is one of the elements of a 2-dimensional array using the standard Collection.isIn matcher provided with Hamcrest library. Unfortunately receiving the following assertion exception:

java.lang.AssertionError: 
Expected: one of {["A", "B", "C"], ["A", "B", "C"]}
   but: was ["A", "B", "C"]

Code:

String[][] expected = new String[][] { { "A", "B", "C" }, { "A", "B", "C" } };
String[] actual = new String[] { "A", "B", "C" };

assertThat(actual, isIn(expected));

Can I validate using hamcrest in such a manner? Or do I need to create my own matcher for the given scenario?

Answer 1

The issue is that Object.equals() doesn't do what you might expect when the objects are arrays. As you probably already know, you have to use Arrays.equals() -- but Hamcrest isIn() does not allow for this.

Probably the simplest solution is to convert to List even if only for the test -- because List.equals() works as Hamcrest expects:

...
import static org.hamcrest.CoreMatchers.is;
import static org.hamcrest.collection.IsIn.in;
...

String[][] expected = new String[][] { { "A", "B", "C" }, { "A", "B", "C" } };

Object[] expectedLists = Arrays.stream(expected).map(Arrays::asList).toArray();

String[] actual = new String[] { "A", "B", "C" };

assertThat(Arrays.asList(actual), is(in(expectedLists)));