test: Use mockable time in GuessVerificationProgress

Also add a test.

src/kernel/chainparams.cpp

@@ -613,9 +613,9 @@ public:
         };
 
         chainTxData = ChainTxData{
-            0,
+            .nTime = 0,
-            0,
+            .tx_count = 0,
-            0
+            .dTxRate = 0.001, // Set a non-zero rate to make it testable
         };
 
         base58Prefixes[PUBKEY_ADDRESS] = std::vector<unsigned char>(1,111);

src/validation.cpp

@@ -5572,7 +5572,7 @@ double ChainstateManager::GuessVerificationProgress(const CBlockIndex* pindex) c
         return 0.0;
     }
 
-    int64_t nNow = time(nullptr);
+    const int64_t nNow{TicksSinceEpoch<std::chrono::seconds>(NodeClock::now())};
 
     double fTxTotal;
 

test/functional/rpc_blockchain.py

@@ -101,6 +101,7 @@ class BlockchainTest(BitcoinTestFramework):
         self._test_waitforblockheight()
         self._test_getblock()
         self._test_getdeploymentinfo()
+        self._test_verificationprogress()
         self._test_y2106()
         assert self.nodes[0].verifychain(4, 0)
 
@@ -280,6 +281,14 @@ class BlockchainTest(BitcoinTestFramework):
         # calling with an explicit hash works
         self.check_signalling_deploymentinfo_result(self.nodes[0].getdeploymentinfo(gbci207["bestblockhash"]), gbci207["blocks"], gbci207["bestblockhash"], "started")
 
+    def _test_verificationprogress(self):
+        self.log.info("Check that verificationprogress is less than 1 when the block tip is old")
+        future = 2 * 60 * 60
+        self.nodes[0].setmocktime(self.nodes[0].getblockchaininfo()["time"] + future + 1)
+        assert_greater_than(1, self.nodes[0].getblockchaininfo()["verificationprogress"])
+        self.nodes[0].setmocktime(self.nodes[0].getblockchaininfo()["time"] + future)
+        assert_greater_than(1, self.nodes[0].getblockchaininfo()["verificationprogress"])
+
     def _test_y2106(self):
         self.log.info("Check that block timestamps work until year 2106")
         self.generate(self.nodes[0], 8)[-1]