private void fillServerMap() {
   registerWithServerMap(firstKey);
   for (int i = 0; i < (numKeys - 2); i++) {
     registerWithServerMap("middle" + i);
   }
   registerWithServerMap(lastKey);
   assertThat(serverStore.get(lastKey), is(maxValue - 1));
 }
 @Test
 public void lastKeyReturnsMaxValue() {
   fillServerMap();
   assertThat(serverStore.get(lastKey), is(maxValue - 1));
 }
 @Test
 public void firstKeyReturnsMinValue() {
   fillServerMap();
   assertThat(serverStore.get(firstKey), is(minValue));
 }
 @Test
 public void getNonexistingReturnsNull() {
   fillServerMap();
   assertNull(serverStore.get("unusedKey"));
 }