diff --git a/builder_test.go b/builder_test.go
index 7a021ee..82c3b1c 100644
--- a/builder_test.go
+++ b/builder_test.go
@@ -6,7 +6,32 @@ import (
 	mh "github.com/multiformats/go-multihash"
 )
 
-func TestFormatV1(t *testing.T) {
+func TestV0Builder(t *testing.T) {
+	data := []byte("this is some test content")
+
+	// Construct c1
+	format := V0Builder{}
+	c1, err := format.Sum(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Construct c2
+	hash, err := mh.Sum(data, mh.SHA2_256, -1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	c2 := NewCidV0(hash)
+
+	if !c1.Equals(c2) {
+		t.Fatal("cids mismatch")
+	}
+	if c1.Prefix() != c2.Prefix() {
+		t.Fatal("prefixes mismatch")
+	}
+}
+
+func TestV1Builder(t *testing.T) {
 	data := []byte("this is some test content")
 
 	// Construct c1
@@ -31,27 +56,37 @@ func TestFormatV1(t *testing.T) {
 	}
 }
 
-func TestFormatV0(t *testing.T) {
+func TestCodecChange(t *testing.T) {
+	t.Run("Prefix-CidV0", func(t *testing.T) {
+		p := Prefix{Version: 0, Codec: DagProtobuf, MhType: mh.SHA2_256, MhLength: mh.DefaultLengths[mh.SHA2_256]}
+		testCodecChange(t, p)
+	})
+	t.Run("Prefix-CidV1", func(t *testing.T) {
+		p := Prefix{Version: 1, Codec: DagProtobuf, MhType: mh.SHA2_256, MhLength: mh.DefaultLengths[mh.SHA2_256]}
+		testCodecChange(t, p)
+	})
+	t.Run("V0Builder", func(t *testing.T) {
+		testCodecChange(t, V0Builder{})
+	})
+	t.Run("V1Builder", func(t *testing.T) {
+		testCodecChange(t, V1Builder{Codec: DagProtobuf, HashFun: mh.SHA2_256})
+	})
+}
+
+func testCodecChange(t *testing.T, b Builder) {
 	data := []byte("this is some test content")
 
-	// Construct c1
-	format := V0Builder{}
-	c1, err := format.Sum(data)
+	if b.GetCodec() != DagProtobuf {
+		t.Fatal("original builder not using Protobuf codec")
+	}
+
+	b = b.WithCodec(Raw)
+	c, err := b.Sum(data)
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	// Construct c2
-	hash, err := mh.Sum(data, mh.SHA2_256, -1)
-	if err != nil {
-		t.Fatal(err)
-	}
-	c2 := NewCidV0(hash)
-
-	if !c1.Equals(c2) {
-		t.Fatal("cids mismatch")
-	}
-	if c1.Prefix() != c2.Prefix() {
-		t.Fatal("prefixes mismatch")
+	if c.Type() != Raw {
+		t.Fatal("new cid codec did not change to Raw")
 	}
 }