core: make test chain format compatible with mainnet

Write uint32 length before every block.

pkg/core/helper_test.go

@@ -275,6 +275,7 @@ func _(t *testing.T) {
 		buf := io.NewBufBinWriter()
 		b.EncodeBinary(buf.BinWriter)
 		bytes := buf.Bytes()
+		writer.WriteU32LE(uint32(len(bytes)))
 		writer.WriteBytes(bytes)
 		require.NoError(t, writer.Err)
 	}

pkg/rpc/server/server_helper_test.go

@@ -52,6 +52,7 @@ func initServerWithInMemoryChain(t *testing.T) (*core.Blockchain, http.HandlerFu
 	nBlocks = br.ReadU32LE()
 	require.Nil(t, br.Err)
 	for i := 0; i < int(nBlocks); i++ {
+		_ = br.ReadU32LE()
 		b := &block.Block{}
 		b.DecodeBinary(br)
 		require.Nil(t, br.Err)