T unrelated = groups.get(unrelatedGroupNumber).get(unrelatedItemNumber);
try {
assertion.assertUnrelated(item, unrelated);
} catch (TestAssertionFailure e) {
// TODO(gak): special handling for ComparisonFailure?
throw new TestAssertionFailure(e.getMessage()
.replace("$ITEM", itemString(item, groupNumber, itemNumber))
.replace("$UNRELATED", itemString(unrelated, unrelatedGroupNumber, unrelatedItemNumber)));
}
}