message: Add test for `BlockHeadersBatch` correctly returning a lack of switch block
diff: @@ -3379,4 +3379,25 @@ mod tests {
  assert_eq!(expected_switch_block_height, actual_switch_block_height);
  }
  +
  + #[test]
  + fn returns_no_latest_switch_block_when_absent() {
  + let rng = TestRng::new();
  + let test_block = TestBlockSpec::new(rng, None);
  +
  + let mut test_block_iter = test_block.into_iter();
  +
  + let mut batch = test_block_iter
  + .by_ref()
  + .take(10)
  + .map(|block| block.take_header())
  + .collect::<Vec<_>>();
  + batch.reverse();
  +
  + let batch = BlockHeadersBatch::new(batch);
  +
  + let actual_switch_block_height = batch.latest_switch_block_header();
  +
  + assert!(actual_switch_block_height.is_none());
  + }
  }
  