add diff is zero test

test/libethereum/BlockTestsFiller/bcInvalidHeaderTestFiller.json

@@ -353,6 +353,65 @@
         ]
     },
 
+    "DifficultyIsZero" : {
+        "genesisBlockHeader" : {
+            "bloom" : "00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
+            "coinbase" : "0x8888f1f195afa192cfee860698584c030f4c9db1",
+            "difficulty" : "131072",
+            "extraData" : "0x42",
+            "gasLimit" : "3141592",
+            "gasUsed" : "0",
+            "mixHash" : "0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421",
+            "nonce" : "0x0102030405060708",
+            "number" : "0",
+            "parentHash" : "0x0000000000000000000000000000000000000000000000000000000000000000",
+            "receiptTrie" : "0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421",
+            "stateRoot" : "0xf99eb1626cfa6db435c0836235942d7ccaa935f1ae247d3f1c21e495685f903a",
+            "timestamp" : "0x54c98c81",
+            "transactionsTrie" : "0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421",
+            "uncleHash" : "0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347"
+        },
+        "expect" : {
+            "095e7baea6a6c7c4c2dfeb977efac326af552d87" : {
+                "balance" : "100"
+            }
+        },
+        "pre" : {
+            "a94f5374fce5edbc8e2a8697c15331677e6ebf0b" : {
+                "balance" : "100000000000",
+                "nonce" : "0",
+                "code" : "",
+                "storage": {}
+            },
+            "095e7baea6a6c7c4c2dfeb977efac326af552d87" : {
+                "balance" : "100",
+                "nonce" : "0",
+                "code" : "{ (MSTORE 0 0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff) (LOG1 0 32 0) }",
+                "storage": {}
+            }
+        },
+        "blocks" : [
+            {
+                "blockHeader" : {
+                    "difficulty" : "0"
+                },
+                "transactions" : [
+                    {
+                        "data" : "",
+                        "gasLimit" : "50000",
+                        "gasPrice" : "10",
+                        "nonce" : "0",
+                        "secretKey" : "45a915e4d060149eb4365960e6a7a45f334393093061116b197e3240065ff2d8",
+                        "to" : "095e7baea6a6c7c4c2dfeb977efac326af552d87",
+                        "value" : "5000"
+                    }
+                ],
+                "uncleHeaders" : [
+                ]
+            }
+        ]
+    },
+
     "DifferentExtraData1025" : {
         "genesisBlockHeader" : {
             "bloom" : "00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",

test/libethereum/blockchain.cpp

@@ -685,7 +685,7 @@ void overwriteBlockHeader(BlockInfo& _header, mObject& _blObj)
 			tmp.extraData = importByteArray(ho["extraData"].get_str());
 
 		// find new valid nonce
-		if (tmp != _header)
+		if (tmp != _header && tmp.difficulty)
 			mine(tmp);
 
 		if (ho.count("mixHash"))