diff --git a/core/Blockchain.go b/core/Blockchain.go
index deeb576..761a875 100644
--- a/core/Blockchain.go
+++ b/core/Blockchain.go
@@ -21,12 +21,12 @@ func (bc *Blockchain) MineBlock() Block {
 	// Mine Block
 	log.Print("Mining Block...")
 	for {
-		if strings.HasPrefix(block.Hash(), "00000") {
+		if strings.HasPrefix(block.Hash(), "0000") {
 
 			bc.Blocks = append(bc.Blocks, block)
 			bc.PendingTransactions = []Transaction{}
 
-			log.Print("Block Added: ", block.Hash)
+			log.Print("Block Added: ", block.Hash())
 			return block
 		}
 		block.Proof++
@@ -62,6 +62,17 @@ func (bc *Blockchain) GetLastHash() string {
 	return bc.Blocks[len(bc.Blocks)-1].Hash()
 }
 
+// IsValid checks, if the chain has any faulty blocks
+func (bc *Blockchain) IsValid() bool {
+	for i := 1; i < len(bc.Blocks); i++ {
+		if bc.Blocks[i-1].Hash() != bc.Blocks[i].PreviousHash {
+			return false
+		}
+	}
+
+	return true
+}
+
 // JSONBlockchain is needed, because the hash of each block is calculated dynamically, and therefore is not stored in the `Block` struct
 type JSONBlockchain struct {
 	Blocks              []JSONBlock
diff --git a/core/block_test.go b/core/block_test.go
index 2e6443a..9a8bc95 100644
--- a/core/block_test.go
+++ b/core/block_test.go
@@ -1,18 +1 @@
 package core
-
-import (
-	"testing"
-)
-
-func TestBlock_AddTransaction(t *testing.T) {
-	block := Block{}
-	transaction := Transaction{Sender: "foo", Receiver: "bar", Message: "Test", Amount: 100}
-	block.AddTransaction(transaction)
-
-	want := transaction
-	got := block.Data[0]
-
-	if want != got {
-		t.Errorf("Want: %v, but got %v", want, got)
-	}
-}
diff --git a/core/blockchain_test.go b/core/blockchain_test.go
index b3f22c1..4dde69f 100644
--- a/core/blockchain_test.go
+++ b/core/blockchain_test.go
@@ -4,8 +4,8 @@ import (
 	"testing"
 )
 
-func Test_generateGenesisBlock(t *testing.T) {
-	genesisBlock := generateGenesisBlock()
+func Test_hasGenesisBlock(t *testing.T) {
+	genesisBlock := NewBlockchain().Blocks[0]
 
 	if len(genesisBlock.PreviousHash) > 1 {
 		t.Errorf("Previous hash of Genesis Block is not empty!")
@@ -23,10 +23,34 @@ func TestNewBlockchain(t *testing.T) {
 func TestBlockchain_GetLastHash(t *testing.T) {
 	blockchain := NewBlockchain()
 
-	blockchain.MineBlock(Block{})
-	want := blockchain.Blocks[1].Hash
+	blockchain.MineBlock()
+	want := blockchain.Blocks[1].Hash()
 	got := blockchain.GetLastHash()
 	if got != want {
 		t.Errorf("Want: %v, but got %v", want, got)
 	}
 }
+
+func TestBlockchain_IsValid(t *testing.T) {
+	blockchain := NewBlockchain()
+	blockchain.MineBlock()
+
+	want := true
+	got := blockchain.IsValid()
+	if got != want {
+		t.Errorf("Want: %v, but got %v", want, got)
+	}
+}
+
+func TestBlockchain_IsNotValid(t *testing.T) {
+	blockchain := NewBlockchain()
+	blockchain.MineBlock()
+	blockchain.MineBlock()
+	blockchain.Blocks[1].Proof++
+
+	want := false
+	got := blockchain.IsValid()
+	if got != want {
+		t.Errorf("Want: %v, but got %v", want, got)
+	}
+}
diff --git a/server/webserver.go b/server/webserver.go
index 6903cc3..42b4d41 100644
--- a/server/webserver.go
+++ b/server/webserver.go
@@ -32,6 +32,7 @@ func registerRouteHandlers() {
 	http.HandleFunc("/mine_block", handleMineBlock)
 	http.HandleFunc("/pending_transactions", handleListPendingTransactions)
 	http.HandleFunc("/add_transaction", handleAddTransaction)
+	http.HandleFunc("/is_valid", handleIsValid)
 }
 
 func handleError(err error, w http.ResponseWriter, r *http.Request) {
@@ -64,3 +65,8 @@ func handleMineBlock(w http.ResponseWriter, r *http.Request) {
 func handleListPendingTransactions(w http.ResponseWriter, r *http.Request) {
 	json.NewEncoder(w).Encode(blockchain.PendingTransactions)
 }
+
+func handleIsValid(w http.ResponseWriter, r *http.Request) {
+	valid := blockchain.IsValid()
+	json.NewEncoder(w).Encode(valid)
+}