While investigating #4157, I noticed that contains / doesNotContain assertions have the opposite behavior of Set::contains in case of instances with array elements.

For example:

Set<String[]> actual = Set.of(array("Homer"), array("Marge"));
String[] expected = array("Homer");

assertThat(actual.contains(expected)).isFalse(); // succeeds

assertThat(actual).contains(expected); // succeeds
assertThat(actual).doesNotContain(expected); // fails

This is due to the current implementation of iterableContains in StandardComparisonStrategy:

which delegates the comparison to areEqual, mimicking Objects::deepEquals under the hood.

However, when introducing the changes in #4157 to retain collection semantics, such a deep array comparison of collection elements is no longer performed, and the issue manifests in the current test cases.