private void verifyPoolState(ExpectedState expectedState) {
    verifyPoolState(reserveFileDir, expectedState);
  }
Verify that the layout of the pool matches the expected state.
@param expectedState an {@link ExpectedState} object that describes the expected number of reserve files for each
                     size, or {@code null} if the directory should not exist.
ambry-store/src/test/java/com/github/ambry/store/DiskSpaceAllocatorTest.java