@Test
public void testRefresh() {

    subject.put(FIRST_TEST_KEY, CACHE_ACTION);
    String value1 = subject.get(FIRST_TEST_KEY);
    // refresh item
    String value2 = subject.refresh(FIRST_TEST_KEY);
    assertNotEquals(value1, value2);
    // refresh all
    final Collection<String> expectedValues = new LinkedList<>();
    expectedValues.add(value2);
    final Collection<String> values = subject.refreshAll();
    assertNotEquals(expectedValues, values);
}