@Test
  public void testKeys() throws CacheException {
    String name = getUniqueName();

    Region<Object, Object> region = createRegion(name);
    assertEquals(0, region.keySet().size());

    region.put("A", "a");
    region.put("B", "b");
    region.put("C", "c");

    {
      Set keys = region.keySet();
      assertEquals(3, keys.size());

      assertTrue(keys.contains("A"));
      assertTrue(keys.contains("B"));
      assertTrue(keys.contains("C"));
    }
  }
Tests the {@link Region#keySet()} method.
geode-dunit/src/main/java/org/apache/geode/cache30/RegionTestCase.java