diff --git a/blocks/blocks.go b/blocks/blocks.go
index d5f4df700a1..c41e1323a11 100644
--- a/blocks/blocks.go
+++ b/blocks/blocks.go
@@ -11,6 +11,8 @@ import (
 	u "gx/ipfs/QmZNVWh8LLjAavuQ2JXuFmuYH3C11xo988vSgp7UQrTRj1/go-ipfs-util"
 )
 
+var ErrWrongHash = errors.New("data did not match given hash!")
+
 type Block interface {
 	Multihash() mh.Multihash
 	Data() []byte
@@ -37,7 +39,7 @@ func NewBlockWithHash(data []byte, h mh.Multihash) (*BasicBlock, error) {
 	if u.Debug {
 		chk := u.Hash(data)
 		if string(chk) != string(h) {
-			return nil, errors.New("Data did not match given hash!")
+			return nil, ErrWrongHash
 		}
 	}
 	return &BasicBlock{data: data, multihash: h}, nil
diff --git a/blocks/blocks_test.go b/blocks/blocks_test.go
index 53a85227575..1fecff84457 100644
--- a/blocks/blocks_test.go
+++ b/blocks/blocks_test.go
@@ -1,6 +1,12 @@
 package blocks
 
-import "testing"
+import (
+	"bytes"
+	"testing"
+
+	mh "gx/ipfs/QmYf7ng2hG5XBtJA3tN34DQ2GUN5HNksEw1rLDkmr6vGku/go-multihash"
+	u "gx/ipfs/QmZNVWh8LLjAavuQ2JXuFmuYH3C11xo988vSgp7UQrTRj1/go-ipfs-util"
+)
 
 func TestBlocksBasic(t *testing.T) {
 
@@ -14,3 +20,77 @@ func TestBlocksBasic(t *testing.T) {
 	// Test some data
 	NewBlock([]byte("Hello world!"))
 }
+
+func TestData(t *testing.T) {
+	data := []byte("some data")
+	block := NewBlock(data)
+
+	if !bytes.Equal(block.Data(), data) {
+		t.Error("data is wrong")
+	}
+}
+
+func TestHash(t *testing.T) {
+	data := []byte("some other data")
+	block := NewBlock(data)
+
+	hash, err := mh.Sum(data, mh.SHA2_256, -1)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if !bytes.Equal(block.Multihash(), hash) {
+		t.Error("wrong multihash")
+	}
+}
+
+func TestKey(t *testing.T) {
+	data := []byte("yet another data")
+	block := NewBlock(data)
+	key := block.Key()
+
+	if !bytes.Equal(block.Multihash(), key.ToMultihash()) {
+		t.Error("key contains wrong data")
+	}
+}
+
+func TestManualHash(t *testing.T) {
+	oldDebugState := u.Debug
+	defer (func() {
+		u.Debug = oldDebugState
+	})()
+
+	data := []byte("I can't figure out more names .. data")
+	hash, err := mh.Sum(data, mh.SHA2_256, -1)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	u.Debug = false
+	block, err := NewBlockWithHash(data, hash)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if !bytes.Equal(block.Multihash(), hash) {
+		t.Error("wrong multihash")
+	}
+
+	data[5] = byte((uint32(data[5]) + 5) % 256) // Transfrom hash to be different
+	block, err = NewBlockWithHash(data, hash)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if !bytes.Equal(block.Multihash(), hash) {
+		t.Error("wrong multihash")
+	}
+
+	u.Debug = true
+
+	block, err = NewBlockWithHash(data, hash)
+	if err != ErrWrongHash {
+		t.Fatal(err)
+	}
+
+}