junit - How to compare two Streams in Java 8

Question

What would be a good way to compare two Stream instances in Java 8 and find out whether they have the same elements, specifically for purposes of unit testing?

What I've got now is:

@Test
void testSomething() {
  Stream<Integer> expected;
  Stream<Integer> thingUnderTest;
  // (...)
  Assert.assertArrayEquals(expected.toArray(), thingUnderTest.toArray());
}

or alternatively:

Assert.assertEquals(
    expected.collect(Collectors.toList()),
    thingUnderTest.collect(Collectors.toList()));

But that means I'm constructing two collections and discarding them. It's not a performance issue, given the size of my test streams, but I'm wondering whether there's a canonical way to compare two streams.

Answer 1

static void assertStreamEquals(Stream<?> s1, Stream<?> s2) {
    Iterator<?> iter1 = s1.iterator(), iter2 = s2.iterator();
    while(iter1.hasNext() && iter2.hasNext())
        assertEquals(iter1.next(), iter2.next());
    assert !iter1.hasNext() && !iter2.hasNext();
}