diff --git a/pkg/stringutil/utils.go b/pkg/stringutil/utils.go
index e303eba..c91ff85 100644
--- a/pkg/stringutil/utils.go
+++ b/pkg/stringutil/utils.go
@@ -2,7 +2,7 @@ package stringutil
 
 import (
 	"crypto/sha1"
-	"fmt"
+	"encoding/hex"
 	"io"
 	"net/mail"
 	"strings"
@@ -13,10 +13,11 @@ import (
 func HashMailboxName(mailbox string) string {
 	h := sha1.New()
 	if _, err := io.WriteString(h, mailbox); err != nil {
-		// This shouldn't ever happen
+		// This should never happen.
 		return ""
 	}
-	return fmt.Sprintf("%x", h.Sum(nil))
+
+	return hex.EncodeToString(h.Sum(nil))
 }
 
 // StringAddress converts an Address to a UTF-8 string.
diff --git a/pkg/stringutil/utils_test.go b/pkg/stringutil/utils_test.go
index 1bfa638..e6fdbfe 100644
--- a/pkg/stringutil/utils_test.go
+++ b/pkg/stringutil/utils_test.go
@@ -6,14 +6,17 @@ import (
 	"testing"
 
 	"github.com/inbucket/inbucket/v3/pkg/stringutil"
+	"github.com/stretchr/testify/assert"
 )
 
 func TestHashMailboxName(t *testing.T) {
-	want := "1d6e1cf70ec6f9ab28d3ea4b27a49a77654d370e"
-	got := stringutil.HashMailboxName("mail")
-	if got != want {
-		t.Errorf("Got %q, want %q", got, want)
-	}
+	want := "da39a3ee5e6b4b0d3255bfef95601890afd80709"
+	got := stringutil.HashMailboxName("")
+	assert.Equal(t, want, got, "for empty string")
+
+	want = "1d6e1cf70ec6f9ab28d3ea4b27a49a77654d370e"
+	got = stringutil.HashMailboxName("mail")
+	assert.Equal(t, want, got, "for 'mail'")
 }
 
 func TestStringAddressList(t *testing.T) {
diff --git a/pkg/test/integration_test.go b/pkg/test/integration_test.go
index 6246875..7f9ef77 100644
--- a/pkg/test/integration_test.go
+++ b/pkg/test/integration_test.go
@@ -43,7 +43,7 @@ type IntegrationSuite struct {
 
 func (s *IntegrationSuite) SetupSuite() {
 	stopServer, err := startServer()
-	s.NoError(err)
+	s.Require().NoError(err)
 	s.stopServer = stopServer
 }