add some tests for Blockchain

Author: fluency03

src/main/scala/com/fluency03/blockchain/core/Blockchain.scala

@@ -6,6 +6,8 @@ import com.fluency03.blockchain.core.Blockchain._
 import org.json4s.native.JsonMethods.{compact, render}
 import org.json4s.{Extraction, JValue}
 
+import scala.annotation.tailrec
+
 /**
  * Blockchain with difficulty and the chain of Blocks.
  * @param difficulty Difficulty of a Blockchain
@@ -45,6 +47,7 @@ object Blockchain {
 
   def apply(difficulty: Int): Blockchain = new Blockchain(difficulty, Seq(Block.genesis(difficulty)))
 
+  @tailrec
   def isValidChain(chain: Seq[Block]): Boolean = chain match {
     case Nil => true
     case g +: Nil => g.previousHash == ZERO64 && g.index == 0 && g.hasValidHash

src/main/scala/com/fluency03/blockchain/core/Merkle.scala

@@ -1,9 +1,12 @@
 package com.fluency03.blockchain
 package core
 
+import scala.annotation.tailrec
+
 object Merkle {
   def computeRoot(trans: Seq[Transaction]): String = computeRootOfHashes(trans.map(_.id))
 
+  @tailrec
   def computeRootOfHashes(hashes: Seq[String]): String = hashes.length match {
     case 0 => ZERO64
     case 1 => hashes.head

src/test/scala/com/fluency03/blockchain/core/BlockchainTest.scala

@@ -1,6 +1,7 @@
 package com.fluency03.blockchain
 package core
 
+import com.fluency03.blockchain.core.Blockchain.isValidChain
 import com.fluency03.blockchain.core.Transaction.createCoinbaseTx
 import org.json4s.JsonDSL._
 import org.json4s.JValue
@@ -64,10 +65,16 @@ class BlockchainTest extends FlatSpec with Matchers  {
     blockchainAdded.lastBlock().get shouldEqual expected
     blockchainAdded.isValid shouldEqual true
     blockchainAdded.length shouldEqual 2
+
+    val blockchainAdded2 = blockchainToAdd.addBlock("This is next Block!", Seq(t1, t2))
+    blockchainAdded2.lastBlock().get shouldEqual expected
+    blockchainAdded2.isValid shouldEqual true
+    blockchainAdded2.length shouldEqual 2
   }
 
   "Blockchain" should "have be validatable." in {
     // TODO (Chang): isValidChain
+    isValidChain(Nil) shouldEqual false
   }
 
 }