test: add transport layer (#97)

The purpose of transport layer is to abstract the way to send messages and setup connections between peers in a p2p network. The peer discovery is simulated by a hosted server: every peer sends its address to a known server. Once collecting enough peers, respond the whole peers lists to all peers.

Changes:
- Add test.Trasnport interface
- Add test.Transport implementation by golang channel.
- Add test.transport implementation by TCP connection.
- Move LatencyModel to core/test package
- Add Marshaller interface

1 files changed, 4 insertions, 4 deletions

diff --git a/integration_test/validator.go b/integration_test/validator.go
index bfe517f..5909b46 100644
--- a/integration_test/validator.go
+++ b/integration_test/validator.go
@@ -68,8 +68,8 @@ type Validator struct {
 	chainID          uint32
 	cons             *core.Consensus
 	gov              core.Governance
-	networkLatency   LatencyModel
-	proposingLatency LatencyModel
+	networkLatency   test.LatencyModel
+	proposingLatency test.LatencyModel
 }
 
 // NewValidator constructs an instance of Validator.
@@ -79,8 +79,8 @@ func NewValidator(
 	db blockdb.BlockDatabase,
 	privateKey crypto.PrivateKey,
 	vID types.ValidatorID,
-	networkLatency LatencyModel,
-	proposingLatency LatencyModel) *Validator {
+	networkLatency test.LatencyModel,
+	proposingLatency test.LatencyModel) *Validator {
 
 	hashes := make(common.Hashes, 0)
 	for vID := range gov.GetValidatorSet() {