diff --git a/examples/sha1/asm.go b/examples/sha1/asm.go
index 8888ad0..6ad6581 100644
--- a/examples/sha1/asm.go
+++ b/examples/sha1/asm.go
@@ -5,7 +5,7 @@ package main
 import (
 	. "github.com/mmcloughlin/avo/build"
 	. "github.com/mmcloughlin/avo/operand"
-	"github.com/mmcloughlin/avo/reg"
+	. "github.com/mmcloughlin/avo/reg"
 )
 
 func main() {
@@ -37,7 +37,7 @@ func main() {
 
 	// Generate round updates.
 	quarter := []struct {
-		F func(reg.Register, reg.Register, reg.Register) reg.Register
+		F func(Register, Register, Register) Register
 		K uint32
 	}{
 		{choose, 0x5a827999},
@@ -95,7 +95,7 @@ func main() {
 	Generate()
 }
 
-func choose(b, c, d reg.Register) reg.Register {
+func choose(b, c, d Register) Register {
 	r := GP32v()
 	MOVL(d, r)
 	XORL(c, r)
@@ -104,7 +104,7 @@ func choose(b, c, d reg.Register) reg.Register {
 	return r
 }
 
-func xor(b, c, d reg.Register) reg.Register {
+func xor(b, c, d Register) Register {
 	r := GP32v()
 	MOVL(b, r)
 	XORL(c, r)
@@ -112,7 +112,7 @@ func xor(b, c, d reg.Register) reg.Register {
 	return r
 }
 
-func majority(b, c, d reg.Register) reg.Register {
+func majority(b, c, d Register) Register {
 	t, r := GP32v(), GP32v()
 	MOVL(b, t)
 	ORL(c, t)
diff --git a/examples/sha1/sha1.go b/examples/sha1/sha1.go
new file mode 100644
index 0000000..a1159fd
--- /dev/null
+++ b/examples/sha1/sha1.go
@@ -0,0 +1,44 @@
+package sha1
+
+import (
+	"encoding/binary"
+)
+
+const (
+	Size      = 20
+	BlockSize = 64
+)
+
+func Sum(data []byte) [Size]byte {
+	n := len(data)
+	h := [5]uint32{0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476, 0xc3d2e1f0}
+
+	// Consume full blocks.
+	for len(data) >= BlockSize {
+		block(&h, data)
+		data = data[BlockSize:]
+	}
+
+	// Final block.
+	tmp := make([]byte, BlockSize)
+	copy(tmp[:], data)
+	tmp[len(data)] = 0x80
+
+	if len(data) >= 56 {
+		block(&h, tmp)
+		for i := 0; i < BlockSize; i++ {
+			tmp[i] = 0
+		}
+	}
+
+	binary.BigEndian.PutUint64(tmp[56:], uint64(8*n))
+	block(&h, tmp)
+
+	// Write into byte array.
+	var digest [Size]byte
+	for i := 0; i < 5; i++ {
+		binary.BigEndian.PutUint32(digest[4*i:], h[i])
+	}
+
+	return digest
+}
diff --git a/examples/sha1/sha1_test.go b/examples/sha1/sha1_test.go
index 892762f..b06fd2a 100644
--- a/examples/sha1/sha1_test.go
+++ b/examples/sha1/sha1_test.go
@@ -1,26 +1,46 @@
 package sha1
 
 import (
-	"log"
-	"reflect"
+	"bytes"
+	"crypto/sha1"
+	"encoding/hex"
 	"testing"
+	"testing/quick"
 )
 
 //go:generate go run asm.go -out sha1.s -stubs stub.go
 
-func TestEmptyString(t *testing.T) {
-	h := [...]uint32{0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476, 0xc3d2e1f0}
-	m := make([]byte, 64)
-	m[0] = 0x80
-
-	block(&h, m)
-
-	expect := [...]uint32{0xda39a3ee, 0x5e6b4b0d, 0x3255bfef, 0x95601890, 0xafd80709}
-
-	for i := 0; i < 5; i++ {
-		log.Printf("h[%d] = %08x", i, h[i])
+func TestVectors(t *testing.T) {
+	cases := []struct {
+		Data      string
+		HexDigest string
+	}{
+		{"", "da39a3ee5e6b4b0d3255bfef95601890afd80709"},
+		{"The quick brown fox jumps over the lazy dog", "2fd4e1c67a2d28fced849ee1bb76e7391b93eb12"},
+		{"The quick brown fox jumps over the lazy cog", "de9f2c7fd25e1b3afad3e85a0bd17d9b100db4b3"},
 	}
-	if !reflect.DeepEqual(expect, h) {
-		t.Fatal("incorrect hash")
+	for _, c := range cases {
+		digest := Sum([]byte(c.Data))
+		got := hex.EncodeToString(digest[:])
+		if got != c.HexDigest {
+			t.Errorf("Sum(%#v) = %s; expect %s", c.Data, got, c.HexDigest)
+		}
+	}
+}
+
+func TestCmp(t *testing.T) {
+	if err := quick.CheckEqual(Sum, sha1.Sum, nil); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestLengths(t *testing.T) {
+	data := make([]byte, BlockSize)
+	for n := 0; n <= BlockSize; n++ {
+		got := Sum(data[:n])
+		expect := sha1.Sum(data[:n])
+		if !bytes.Equal(got[:], expect[:]) {
+			t.Errorf("failed on length %d", n)
+		}
 	}
 }