diff --git a/gauth/gauth_test.go b/gauth/gauth_test.go
new file mode 100644
index 0000000..4bed176
--- /dev/null
+++ b/gauth/gauth_test.go
@@ -0,0 +1,30 @@
+package gauth_test
+
+import (
+	"testing"
+
+	"github.com/pcarrier/gauth/gauth"
+)
+
+func TestCode(t *testing.T) {
+	tests := []struct {
+		secret string
+		index  int64
+		want   string
+		fail   bool
+	}{
+		// Manually verified with the Google authenticator app.
+		{"ABCDEFGH", 51790421, "305441", false},
+
+		// Invalid Base32 input for the secret.
+		{"blargh!", 123, "", true},
+	}
+	for _, test := range tests {
+		got, err := gauth.Code(test.secret, test.index)
+		if err != nil && !test.fail {
+			t.Errorf("Code(%q, %d): unexpected error: %v", test.secret, test.index, err)
+		} else if got != test.want {
+			t.Errorf("Code(%q, %d): got %q, want %q", test.secret, test.index, got, test.want)
+		}
+	}
+}