test: Add loadtxoutset test with tip on snapshot block

Also pulls out the guarding assert and calls it explicitly before the test function is called. This is already done before the existing call of the test function so it was not needed there.

test/functional/feature_assumeutxo.py

@@ -19,7 +19,6 @@
 Interesting starting states could be loading a snapshot when the current chain tip is:
 
 - TODO: Not an ancestor of the snapshot block but has less work
-- TODO: The snapshot block
 - TODO: Not an ancestor or a descendant of the snapshot block and has more work
 
 """
@@ -197,7 +196,6 @@ def test_invalid_file_path(self):
     def test_snapshot_with_less_work(self, dump_output_path):
         self.log.info("Test bitcoind should fail when snapshot has less accumulated work than this node.")
         node = self.nodes[0]
-        assert_equal(node.getblockcount(), FINAL_HEIGHT)
         with node.assert_debug_log(expected_msgs=["[snapshot] activation failed - work does not exceed active chainstate"]):
             assert_raises_rpc_error(-32603, "Unable to load UTXO snapshot", node.loadtxoutset, dump_output_path)
 
@@ -263,6 +261,11 @@ def run_test(self):
         self.log.info(f"Creating a UTXO snapshot at height {SNAPSHOT_BASE_HEIGHT}")
         dump_output = n0.dumptxoutset('utxos.dat')
 
+        self.log.info("Test loading snapshot when the node tip is on the same block as the snapshot")
+        assert_equal(n0.getblockcount(), SNAPSHOT_BASE_HEIGHT)
+        assert_equal(n0.getblockchaininfo()["blocks"], SNAPSHOT_BASE_HEIGHT)
+        self.test_snapshot_with_less_work(dump_output['path'])
+
         self.log.info("Test loading snapshot when headers are not synced")
         self.test_headers_not_synced(dump_output['path'])