Test network upgrade logic

Also demonstrates how to specify a network upgrade.

src/consensus/upgrades.cpp

@@ -13,6 +13,11 @@ const struct NUInfo NetworkUpgradeInfo[Consensus::MAX_NETWORK_UPGRADES] = {
         /*.nBranchId =*/ 0,
         /*.strName =*/ "Sprout",
         /*.strInfo =*/ "The Zcash network at launch",
+    },
+    {
+        /*.nBranchId =*/ 0x74736554,
+        /*.strName =*/ "Test dummy",
+        /*.strInfo =*/ "Test dummy info",
     }
 };