src/main/java/org/fest/assertions/ItemGroupAssert.java
protected final void assertContainsOnly(@NotNull Object... objects) {
    isNotNull();
    checkNotNull(objects);
    Set<Object> copy = actualAsSet();
    List<Object> notFound = notFoundInCopy(copy, newLinkedHashSet(objects));
    if (!notFound.isEmpty()) {
      throw failureIfExpectedElementsNotFound(notFound);
    }
    if (copy == null || copy.isEmpty()) {
      return;
    }
    throw failureIfUnexpectedElementsFound(copy);
  }
protected final void assertContainsOnly(@NotNull Object... objects) {
    isNotNull();
    checkNotNull(objects);
    Set<Object> copy = actualAsSet();
    List<Object> notFound = notFoundInCopy(copy, newLinkedHashSet(objects));
    if (!notFound.isEmpty()) {
      throw failureIfExpectedElementsNotFound(notFound);
    }
    if (copy == null || copy.isEmpty()) {
      return;
    }
    throw failureIfUnexpectedElementsFound(copy);
  }
Verifies that the actual group of objects contains the given objects <strong>only</strong>, in any order.

@param objects the objects to look for.
@throws AssertionError       if the actual group of objects is {@code null}.
@throws NullPointerException if the given group of objects is {@code null}.
@throws AssertionError       if the actual group of objects does not contain the given objects, or if the actual
group of objects contains elements other than the ones specified.