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POWhy does IsIterableContainingInOrder Hamcrest matcher fail to work with arrays?
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copied!<p>I am obviously confused about how to use Hamcrest's <code>IsIterableContainingInOrder</code> to verify List equality beyond just using <code>.equals()</code>. I'd like to see Hamcrest's helpful messages in my reports.</p> <p>Why are the tests below failing to even compile? Some of them are more counter-intuitive than others, at least for me. I get, I think, the general principle that the type parameter will be inferred to what I pass to a method with a varargs signature so it will consider arrays of T as varargs of T and so will generate a Matcher based on T and not on array of T, iterable of T, or anything like that.</p> <p>I could use an explanation, please, as to why some of the lines that are most intuitive actually fail to even compile.</p> <p>Particularly:</p> <ul> <li>3 and 4 show the asymmetry of array/List</li> <li>5 and 6 show that I can look in a List and not in an array (?)</li> </ul> <p>The compiler warning on the line marked as such is even more mysterious to me.</p> <hr> <pre><code>@org.junit.Test public void testTest() { String string1 = "A"; String string2 = "B"; String string3 = "C"; List<String> list1 = Lists.newArrayList(string1, string2, string3); List<String> list2 = Lists.newArrayList(string1, string2, "C"); String[] array1 = list1.toArray(new String[list1.size()]); String[] array2 = list2.toArray(new String[list2.size()]); // ------------------------------------------------------------------------- // 1) The assertion after this comment line DOES NOT COMPILE // Assert.assertThat(array2, IsIterableContainingInOrder.contains(array1)); // ------------------------------------------------------------------------- // 2) The assertion after this comment line DOES NOT COMPILE // Assert.assertThat(list2, IsIterableContainingInOrder.contains(list1)); // ------------------------------------------------------------------------- // 3) The assertion after this comment line SUCCEEDS Assert.assertThat(list2, IsIterableContainingInOrder.contains(array1)); // ------------------------------------------------------------------------- // 4) The assertion after this comment line DOES NOT COMPILE + HAS WARNING // Assert.assertThat(array2, IsIterableContainingInOrder.contains(list1)); // ------------------------------------------------------------------------- // 5) The assertion after this comment line DOES NOT COMPILE // Assert.assertThat(array2, IsIterableContainingInOrder.contains(string1)); // ------------------------------------------------------------------------- // 6) The assertion after this comment line COMPILES but fails Assert.assertThat(list2, IsIterableContainingInOrder.contains(string1)); // ------------------------------------------------------------------------- // 7) The assertion after this comment line COMPILES and succeeds Assert.assertThat(list2, IsIterableContainingInOrder.contains(string1, string2, string3)); // ------------------------------------------------------------------------- } </code></pre> <hr> <h3>Copious amounts of astonishment. :(</h3> <hr> <p>PS I realise all of the astonishment comes from my own ignorance and nothing else. I should brush up on Generics, type inference, varargs, etc. I could really use a thorough explanation on this, and I would probably refer back to it a few times going forward.</p> <p>PPS I <em>did</em> try to read the code first but look at it for a sec... ;) Not for the feint of heart:</p> <pre><code>@SuppressWarnings("unchecked") @Factory public static <E> Matcher<Iterable<? extends E>> contains(final Matcher<? super E> itemMatcher) { return contains(new ArrayList<Matcher<? super E>>(asList(itemMatcher))); } </code></pre>

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