Make CCoinsViewTest behave like CCoinsViewDB

src/test/coins_tests.cpp

@@ -45,14 +45,17 @@ public:
     bool BatchWrite(CCoinsMap& mapCoins, const uint256& hashBlock)
     {
         for (CCoinsMap::iterator it = mapCoins.begin(); it != mapCoins.end(); ) {
+            if (it->second.flags & CCoinsCacheEntry::DIRTY) {
+                // Same optimization used in CCoinsViewDB is to only write dirty entries.
                 map_[it->first] = it->second.coins;
                 if (it->second.coins.IsPruned() && insecure_rand() % 3 == 0) {
                     // Randomly delete empty entries on write.
                     map_.erase(it->first);
                 }
+            }
             mapCoins.erase(it++);
         }
-        mapCoins.clear();
+        if (!hashBlock.IsNull())
             hashBestBlock_ = hashBlock;
         return true;
     }