@Test(expected = IOException.class)
  public void testCleanUpStagingDirectoryTargetPathDoesNotExist() throws IOException {
    String targetPath = tempDir.getAbsolutePath() + "/nonExistentTarget";
    String stagingDirectoryName = "staging";
    String storeId = "store1";

    // Call cleanUpStagingDirectory
    fileStore.cleanUpStagingDirectory(targetPath, stagingDirectoryName, storeId);
  }
Returns the number of segments remaining in the reserve pool for the given store ID and segment size.
@param storeId the ID of the store.
@param segmentSize the size of the segment.
@return the number of segments remaining in the reserve pool.
ambry-store/src/test/java/com/github/ambry/store/FileStoreTest.java