diff --git a/pkg/users/utils_test.go b/pkg/users/utils_test.go
new file mode 100644
index 0000000..f1dfa12
--- /dev/null
+++ b/pkg/users/utils_test.go
@@ -0,0 +1,40 @@
+// Copyright (c) 2022 Lukasz Janyst <lukasz@jany.st>
+//
+// This file is part of Peroxide.
+//
+// Peroxide is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Peroxide is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Peroxide.  If not, see <https://www.gnu.org/licenses/>.
+
+package users
+
+import (
+	"testing"
+
+	r "github.com/stretchr/testify/require"
+)
+
+func TestLoginDecoder(t *testing.T) {
+	test := func(login, parsedLogin, parsedKeySlot string) {
+		l, ks := DecodeLogin(login)
+		r.Equal(t, parsedLogin, l)
+		r.Equal(t, parsedKeySlot, ks)
+	}
+
+	test("", "", "main")
+	test("foo@bar@baz", "foo@bar@baz", "main")
+	test("foo..test@bar@baz", "foo..test@bar@baz", "main")
+	test("foo..test..test@bar@baz", "foo..test..test@bar@baz", "main")
+	test("foo", "foo", "main")
+	test("foo@bar", "foo@bar", "main")
+	test("foo..test@bar", "foo@bar", "test")
+}