@Test(timeout=60000)
public void testUncacheUnknownBlock() throws Exception {

  // Create a file
  Path fileName = new Path("/testUncacheUnknownBlock");
  int fileLen = 4096;
  DFSTestUtil.createFile(fs, fileName, fileLen, (short)1, 0xFDFD);
  HdfsBlockLocation[] locs = (HdfsBlockLocation[])fs.getFileBlockLocations(
      fileName, 0, fileLen);
  // Try to uncache it without caching it first
  setHeartbeatResponse(uncacheBlocks(locs));
  GenericTestUtils.waitFor(new Supplier<Boolean>() {
    @Override
    public Boolean get() {
      return fsd.getNumBlocksFailedToUncache() > 0;
    }
  }, 100, 10000);
}