test: Add edge case of pruning up to index height

test/functional/feature_blockfilterindex_prune.py

@@ -24,9 +24,7 @@ class FeatureBlockfilterindexPruneTest(BitcoinTestFramework):
         self.log.info("check if we can access a blockfilter when pruning is enabled but no blocks are actually pruned")
         self.sync_index(height=200)
         assert_greater_than(len(self.nodes[0].getblockfilter(self.nodes[0].getbestblockhash())['filter']), 0)
-        # Mine two batches of blocks to avoid hitting NODE_NETWORK_LIMITED_MIN_BLOCKS disconnection
-        self.generate(self.nodes[0], 250)
-        self.generate(self.nodes[0], 250)
+        self.generate(self.nodes[0], 500)
         self.sync_index(height=700)
 
         self.log.info("prune some blocks")
@@ -39,16 +37,29 @@ class FeatureBlockfilterindexPruneTest(BitcoinTestFramework):
         self.log.info("check if we can access the blockfilter of a pruned block")
         assert_greater_than(len(self.nodes[0].getblockfilter(self.nodes[0].getblockhash(2))['filter']), 0)
 
+        # mine and sync index up to a height that will later be the pruneheight
+        self.generate(self.nodes[0], 298)
+        self.sync_index(height=998)
+
         self.log.info("start node without blockfilterindex")
         self.restart_node(0, extra_args=["-fastprune", "-prune=1"])
 
         self.log.info("make sure accessing the blockfilters throws an error")
         assert_raises_rpc_error(-1, "Index is not enabled for filtertype basic", self.nodes[0].getblockfilter, self.nodes[0].getblockhash(2))
-        self.generate(self.nodes[0], 1000)
+        self.generate(self.nodes[0], 502)
+
+        self.log.info("prune exactly up to the blockfilterindexes best block while blockfilters are disabled")
+        pruneheight_2 = self.nodes[0].pruneblockchain(1000)
+        assert_equal(pruneheight_2, 998)
+        self.restart_node(0, extra_args=["-fastprune", "-prune=1", "-blockfilterindex=1"])
+        self.log.info("make sure that we can continue with the partially synced index after having pruned up to the index height")
+        self.sync_index(height=1500)
 
         self.log.info("prune below the blockfilterindexes best block while blockfilters are disabled")
-        pruneheight_new = self.nodes[0].pruneblockchain(1000)
-        assert_greater_than(pruneheight_new, pruneheight)
+        self.restart_node(0, extra_args=["-fastprune", "-prune=1"])
+        self.generate(self.nodes[0], 1000)
+        pruneheight_3 = self.nodes[0].pruneblockchain(2000)
+        assert_greater_than(pruneheight_3, pruneheight_2)
         self.stop_node(0)
 
         self.log.info("make sure we get an init error when starting the node again with block filters")